Search Results

Search found 602 results on 25 pages for 'chunks'.

Page 23/25 | < Previous Page | 19 20 21 22 23 24 25  | Next Page >

• Interesting things – Twitter annotations and your phone as a web server

  - by jamiet

  I overheard/read a couple of things today that really made me, data junkie that I am, take a step back and think, “Hmmm, yeah, that could be really interesting” and I wanted to make a note of them here so that (a) I could bring them to the attention of anyone that happens to read this and (b) I can maybe come back here in a few years and see if either of these have come to fruition. Your phone as a web server While listening to Jon Udell’s (twitter) “Interviews with Innovators Podcast” today in which he interviewed Herbert Van de Sompel (twitter) about his Momento project. During the interview Jon and Herbert made the following remarks: Jon: [some people] really had this vision of a web of servers, the notion that every node on the internet, every connected entity, is potentially a server and a client…we can see where we’re getting to a point where these endpoint devices we have in our pockets are going to be massively capable and it may be in the not too distant future that significant chunks of the web archive will be cached all over the place including on your own machine… Herbert: wasn’t it Opera who at one point turned your browser into a server? That really got my brain ticking. We all carry a mobile phone with us and therefore we all potentially carry a mobile web server with us as well and to my mind the only thing really stopping that from happening is the capabilities of the phone hardware, the capabilities of the network infrastructure and the will to just bloody do it. Certainly all the standards required for addressing a web server on a phone already exist (to this uninitiated observer DNS and IPv6 seem to solve that problem) so why not? I tweeted about the idea and Rory Street answered back with “why would you want a phone to be a web server?”: Its a fair question and one that I would like to try and answer. Mobile phones are increasingly becoming our window onto the world as we use them to upload messages to Twitter, record our location on FourSquare or interact with our friends on Facebook but in each of these cases some other service is acting as our intermediary; to see what I’m thinking you have to go via Twitter, to see where I am you have to go to FourSquare (I’m using ‘I’ liberally, I don’t actually use FourSquare before you ask). Why should this have to be the case? Why can’t that data be decentralised? Why can’t we be masters of our own data universe? If my phone acted as a web server then I could expose all of that information without needing those intermediary services. I see a time when we can pass around URLs such as the following: http://jamiesphone.net/location/current - Where is Jamie right now? http://jamiesphone.net/location/2010-04-21 – Where was Jamie on 21st April 2010? http://jamiesphone.net/thoughts/current – What’s on Jamie’s mind right now? http://jamiesphone.net/blog – What documents is Jamie sharing with me? http://jamiesphone.net/calendar/next7days – Where is Jamie planning to be over the next 7 days? and those URLs get served off of the phone in our pockets. If we govern that data then we can control who has access to it and (crucially) how long its available for. Want to wipe yourself off the face of the web? its pretty easy if you’re in control of all the data – just turn your phone off. None of this exists today but I look forward to a time when it does. Opera really were onto something last June when they announced Opera Unite (admittedly Unite only works because Opera provide an intermediary DNS-alike system – it isn’t totally decentralised). Opening up Twitter annotations Last week Twitter held their first developer conference called Chirp where they announced an upcoming new feature called ‘Twitter Annotations’; in short this will allow us to attach metadata to a Tweet thus enhancing the tweet itself. Think of it as a richer version of hashtags. To think of it another way Twitter are turning their data into a humongous Entity-Attribute-Value or triple-tuple store. That alone has huge implications both for the web and Twitter as a whole – the ability to enrich that 140 characters data and thus make it more useful is indeed compelling however today I stumbled upon a blog post from Eugene Mandel entitled Tweet Annotations – a Way to a Metadata Marketplace? where he proposed the idea of allowing tweets to have metadata added by people other than the person who tweeted the original tweet. This idea really fascinated me especially when I read some of the potential uses that Eugene and his commenters suggested. They included: Amazon could attach an ISBN to a tweet that mentions a book. Specialist clients apps for book lovers could be built up around this metadata. Advertisers could pay to place adverts in metadata. The revenue generated from those adverts could be shared with the tweeter or people who add the metadata. Granted, allowing anyone to add metadata to a tweet has the potential to create a spam problem the like of which we haven’t even envisaged but spam hasn’t halted the growth of the web and neither should it halt the growth of data annotations either. The original tweeter should of course be able to determine who can add metadata and whether it should be moderated. As Eugene says himself: Opening publishing tweet annotations to anyone will open the way to a marketplace of metadata where client developers, data mining companies and advertisers can add new meaning to Twitter and build innovative businesses. What Eugene and his followers did not mention is what I think is potentially the most fascinating use of opening up annotations. Google’s success today is built on their page rank algorithm that measures the validity of a web page by the number of incoming links to it and the page rank of the sites containing those links – its a system built on reputation. Twitter annotations could open up a new paradigm however – let’s call it People rank- where reputation can be measured by the metadata that people choose to apply to links and the websites containing those links. Its not hard to see why Google and Microsoft have paid big bucks to get access to the Twitter firehose! Neither of these features, phones as a web server or the ability to add annotations to other people’s tweets, exist today but I strongly believe that they could dramatically enhance the web as we know it today. I hope to look back on this blog post in a few years in the knowledge that these ideas have been put into place. @Jamiet Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

  Read the article

• Session memory – who’s this guy named Max and what’s he doing with my memory?

  - by extended_events

  SQL Server MVP Jonathan Kehayias (blog) emailed me a question last week when he noticed that the total memory used by the buffers for an event session was larger than the value he specified for the MAX_MEMORY option in the CREATE EVENT SESSION DDL. The answer here seems like an excellent subject for me to kick-off my new “401 – Internals” tag that identifies posts where I pull back the curtains a bit and let you peek into what’s going on inside the extended events engine. In a previous post (Option Trading: Getting the most out of the event session options) I explained that we use a set of buffers to store the event data before  we write the event data to asynchronous targets. The MAX_MEMORY along with the MEMORY_PARTITION_MODE defines how big each buffer will be. Theoretically, that means that I can predict the size of each buffer using the following formula: max memory / # of buffers = buffer size If it was that simple I wouldn’t be writing this post. I’ll take “boundary” for 64K Alex For a number of reasons that are beyond the scope of this blog, we create event buffers in 64K chunks. The result of this is that the buffer size indicated by the formula above is rounded up to the next 64K boundary and that is the size used to create the buffers. If you think visually, this means that the graph of your max_memory option compared to the actual buffer size that results will look like a set of stairs rather than a smooth line. You can see this behavior by looking at the output of dm_xe_sessions, specifically the fields related to the buffer sizes, over a range of different memory inputs: Note: This test was run on a 2 core machine using per_cpu partitioning which results in 5 buffers. (Seem my previous post referenced above for the math behind buffer count.) input_memory_kb total_regular_buffers regular_buffer_size total_buffer_size 637 5 130867 654335 638 5 130867 654335 639 5 130867 654335 640 5 196403 982015 641 5 196403 982015 642 5 196403 982015 This is just a segment of the results that shows one of the “jumps” between the buffer boundary at 639 KB and 640 KB. You can verify the size boundary by doing the math on the regular_buffer_size field, which is returned in bytes: 196403 – 130867 = 65536 bytes 65536 / 1024 = 64 KB The relationship between the input for max_memory and when the regular_buffer_size is going to jump from one 64K boundary to the next is going to change based on the number of buffers being created. The number of buffers is dependent on the partition mode you choose. If you choose any partition mode other than NONE, the number of buffers will depend on your hardware configuration. (Again, see the earlier post referenced above.) With the default partition mode of none, you always get three buffers, regardless of machine configuration, so I generated a “range table” for max_memory settings between 1 KB and 4096 KB as an example. start_memory_range_kb end_memory_range_kb total_regular_buffers regular_buffer_size total_buffer_size 1 191 NULL NULL NULL 192 383 3 130867 392601 384 575 3 196403 589209 576 767 3 261939 785817 768 959 3 327475 982425 960 1151 3 393011 1179033 1152 1343 3 458547 1375641 1344 1535 3 524083 1572249 1536 1727 3 589619 1768857 1728 1919 3 655155 1965465 1920 2111 3 720691 2162073 2112 2303 3 786227 2358681 2304 2495 3 851763 2555289 2496 2687 3 917299 2751897 2688 2879 3 982835 2948505 2880 3071 3 1048371 3145113 3072 3263 3 1113907 3341721 3264 3455 3 1179443 3538329 3456 3647 3 1244979 3734937 3648 3839 3 1310515 3931545 3840 4031 3 1376051 4128153 4032 4096 3 1441587 4324761 As you can see, there are 21 “steps” within this range and max_memory values below 192 KB fall below the 64K per buffer limit so they generate an error when you attempt to specify them. Max approximates True as memory approaches 64K The upshot of this is that the max_memory option does not imply a contract for the maximum memory that will be used for the session buffers (Those of you who read Take it to the Max (and beyond) know that max_memory is really only referring to the event session buffer memory.) but is more of an estimate of total buffer size to the nearest higher multiple of 64K times the number of buffers you have. The maximum delta between your initial max_memory setting and the true total buffer size occurs right after you break through a 64K boundary, for example if you set max_memory = 576 KB (see the green line in the table), your actual buffer size will be closer to 767 KB in a non-partitioned event session. You get “stepped up” for every 191 KB block of initial max_memory which isn’t likely to cause a problem for most machines. Things get more interesting when you consider a partitioned event session on a computer that has a large number of logical CPUs or NUMA nodes. Since each buffer gets “stepped up” when you break a boundary, the delta can get much larger because it’s multiplied by the number of buffers. For example, a machine with 64 logical CPUs will have 160 buffers using per_cpu partitioning or if you have 8 NUMA nodes configured on that machine you would have 24 buffers when using per_node. If you’ve just broken through a 64K boundary and get “stepped up” to the next buffer size you’ll end up with total buffer size approximately 10240 KB and 1536 KB respectively (64K * # of buffers) larger than max_memory value you might think you’re getting. Using per_cpu partitioning on large machine has the most impact because of the large number of buffers created. If the amount of memory being used by your system within these ranges is important to you then this is something worth paying attention to and considering when you configure your event sessions. The DMV dm_xe_sessions is the tool to use to identify the exact buffer size for your sessions. In addition to the regular buffers (read: event session buffers) you’ll also see the details for large buffers if you have configured MAX_EVENT_SIZE. The “buffer steps” for any given hardware configuration should be static within each partition mode so if you want to have a handy reference available when you configure your event sessions you can use the following code to generate a range table similar to the one above that is applicable for your specific machine and chosen partition mode. DECLARE @buf_size_output table (input_memory_kb bigint, total_regular_buffers bigint, regular_buffer_size bigint, total_buffer_size bigint) DECLARE @buf_size int, @part_mode varchar(8) SET @buf_size = 1 -- Set to the begining of your max_memory range (KB) SET @part_mode = 'per_cpu' -- Set to the partition mode for the table you want to generate WHILE @buf_size <= 4096 -- Set to the end of your max_memory range (KB) BEGIN     BEGIN TRY         IF EXISTS (SELECT * from sys.server_event_sessions WHERE name = 'buffer_size_test')             DROP EVENT SESSION buffer_size_test ON SERVER         DECLARE @session nvarchar(max)         SET @session = 'create event session buffer_size_test on server                         add event sql_statement_completed                         add target ring_buffer                         with (max_memory = ' + CAST(@buf_size as nvarchar(4)) + ' KB, memory_partition_mode = ' + @part_mode + ')'         EXEC sp_executesql @session         SET @session = 'alter event session buffer_size_test on server                         state = start'         EXEC sp_executesql @session         INSERT @buf_size_output (input_memory_kb, total_regular_buffers, regular_buffer_size, total_buffer_size)             SELECT @buf_size, total_regular_buffers, regular_buffer_size, total_buffer_size FROM sys.dm_xe_sessions WHERE name = 'buffer_size_test'     END TRY     BEGIN CATCH         INSERT @buf_size_output (input_memory_kb)             SELECT @buf_size     END CATCH     SET @buf_size = @buf_size + 1 END DROP EVENT SESSION buffer_size_test ON SERVER SELECT MIN(input_memory_kb) start_memory_range_kb, MAX(input_memory_kb) end_memory_range_kb, total_regular_buffers, regular_buffer_size, total_buffer_size from @buf_size_output group by total_regular_buffers, regular_buffer_size, total_buffer_size Thanks to Jonathan for an interesting question and a chance to explore some of the details of Extended Event internals. - Mike

  Read the article

• Create PDF document using iTextSharp in ASP.Net 4.0 and MemoryMappedFile

  - by sreejukg

  In this article I am going to demonstrate how ASP.Net developers can programmatically create PDF documents using iTextSharp. iTextSharp is a software component, that allows developers to programmatically create or manipulate PDF documents. Also this article discusses the process of creating in-memory file, read/write data from/to the in-memory file utilizing the new feature MemoryMappedFile. I have a database of users, where I need to send a notice to all my users as a PDF document. The sending mail part of it is not covered in this article. The PDF document will contain the company letter head, to make it more official. I have a list of users stored in a database table named “tblusers”. For each user I need to send customized message addressed to them personally. The database structure for the users is give below. id Title Full Name 1 Mr. Sreeju Nair K. G. 2 Dr. Alberto Mathews 3 Prof. Venketachalam Now I am going to generate the pdf document that contains some message to the user, in the following format. Dear <Title> <FullName>, The message for the user. Regards, Administrator Also I have an image, bg.jpg that contains the background for the document generated. I have created .Net 4.0 empty web application project named “iTextSharpSample”. First thing I need to do is to download the iTextSharp dll from the source forge. You can find the url for the download here. http://sourceforge.net/projects/itextsharp/files/ I have extracted the Zip file and added the itextsharp.dll as a reference to my project. Also I have added a web form named default.aspx to my project. After doing all this, the solution explorer have the following view. In the default.aspx page, I inserted one grid view and associated it with a SQL Data source control that bind data from tblusers. I have added a button column in the grid view with text “generate pdf”. The output of the page in the browser is as follows. Now I am going to create a pdf document when the user clicking on the Generate PDF button. As I mentioned before, I am going to work with the file in memory, I am not going to create a file in the disk. I added an event handler for button by specifying onrowcommand event handler. My gridview source looks like <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataSourceID="SqlDataSource1" Width="481px" CellPadding="4" ForeColor="#333333" GridLines="None" onrowcommand="Generate_PDF" > ………………………………………………………………………….. ………………………………………………………………………….. </asp:GridView> In the code behind, I wrote the corresponding event handler. protected void Generate_PDF(object sender, GridViewCommandEventArgs e) { // The button click event handler code. // I am going to explain the code for this section in the remaining part of the article } The Generate_PDF method is straight forward, It get the title, fullname and message to some variables, then create the pdf using these variables. The code for getting data from the grid view is as follows // get the row index stored in the CommandArgument property int index = Convert.ToInt32(e.CommandArgument); // get the GridViewRow where the command is raised GridViewRow selectedRow = ((GridView)e.CommandSource).Rows[index]; string title = selectedRow.Cells[1].Text; string fullname = selectedRow.Cells[2].Text; string msg = @"There are some changes in the company policy, due to this matter you need to submit your latest address to us. Please update your contact details / personnal details by visiting the member area of the website. ................................... "; since I don’t want to save the file in the disk, I am going the new feature introduced in .Net framework 4, called Memory-Mapped Files. Using Memory-Mapped mapped file, you can created non-persisted memory mapped files, that are not associated with a file in a disk. So I am going to create a temporary file in memory, add the pdf content to it, then write it to the output stream. To read more about MemoryMappedFile, read this msdn article http://msdn.microsoft.com/en-us/library/dd997372.aspx The below portion of the code using MemoryMappedFile object to create a test pdf document in memory and perform read/write operation on file. The CreateViewStream() object will give you a stream that can be used to read or write data to/from file. The code is very straight forward and I included comment so that you can understand the code. using (MemoryMappedFile mmf = MemoryMappedFile.CreateNew("test1.pdf", 1000000)) { // Create a new pdf document object using the constructor. The parameters passed are document size, left margin, right margin, top margin and bottom margin. iTextSharp.text.Document d = new iTextSharp.text.Document(PageSize.A4, 72,72,172,72); //get an instance of the memory mapped file to stream object so that user can write to this using (MemoryMappedViewStream stream = mmf.CreateViewStream()) { // associate the document to the stream. PdfWriter.GetInstance(d, stream); /* add an image as bg*/ iTextSharp.text.Image jpg = iTextSharp.text.Image.GetInstance(Server.MapPath("Image/bg.png")); jpg.Alignment = iTextSharp.text.Image.UNDERLYING; jpg.SetAbsolutePosition(0, 0); //this is the size of my background letter head image. the size is in points. this will fit to A4 size document. jpg.ScaleToFit(595, 842); d.Open(); d.Add(jpg); d.Add(new Paragraph(String.Format("Dear {0} {1},", title, fullname))); d.Add(new Paragraph("\n")); d.Add(new Paragraph(msg)); d.Add(new Paragraph("\n")); d.Add(new Paragraph(String.Format("Administrator"))); d.Close(); } //read the file data byte[] b; using (MemoryMappedViewStream stream = mmf.CreateViewStream()) { BinaryReader rdr = new BinaryReader(stream); b = new byte[mmf.CreateViewStream().Length]; rdr.Read(b, 0, (int)mmf.CreateViewStream().Length); } Response.Clear(); Response.ContentType = "Application/pdf"; Response.BinaryWrite(b); Response.End(); } Press ctrl + f5 to run the application. First I got the user list. Click on the generate pdf icon. The created looks as follows. Summary: Creating pdf document using iTextSharp is easy. You will get lot of information while surfing the www. Some useful resources and references are mentioned below http://itextsharp.com/ http://www.mikesdotnetting.com/Article/82/iTextSharp-Adding-Text-with-Chunks-Phrases-and-Paragraphs http://somewebguy.wordpress.com/2009/05/08/itextsharp-simplify-your-html-to-pdf-creation/ Hope you enjoyed the article.

  Read the article

• Company Review: Google Products

  Google, Inc offers an array of products and services to all of its end-users. However their search capabilities are the foundation for Google’s current success and their primary business focus. Currently, Google offers over twenty different search applications that allow users to search the internet for books, maps, videos, images, products and much more. Their product decisions have allowed users demands to be met while focusing on the free based model. This allows users to access Google data free of charge and indirectly gives Google a strong competitive advantage of other competitors along with the accuracy of the search results. According to Google, Inc, they offer the following types of searching capabilities: Alerts Get email updates on the topics of your choice Blog Search Find blogs on your favorite topics  Books Search the full text of books  Custom Search Create a customized search experience for your community  Desktop Search and personalize your computer  Dictionary Search for definitions of words and phrases Directory Search the web, organized by topic or category Earth Explore the world from your computer Finance Business info, news and interactive charts GOOG-411 Find and connect for free with businesses from your phone  Images Search for images on the web Maps View maps and directions News Search thousands of news stories Patent Search Search the full text of US Patents Product Search Search for stuff to buy Scholar Search scholarly papers Toolbar Add a search box to your browser Trends Explore past and present search trends Videos Search for videos on the web Web Search Search billions of web pages Web Search Features Find movies, music, stocks, books and more mapping Google’s free based business model is only one way it differentiates itself from its competition. There is also a strong focus on the accuracy of search results and the speed in which they are returned to the end-user. Quality function deployment (QFD) is a structured method used to help connect user needs to the design features of a project proposed to address those needs. This method is particularly useful in accounting for needs that are not easily articulated or precisely defined according to the U. S. Department of Transportation Federal Highway Administration. Due to the fact that QFD is so customer driven Google is always in a constant state of change in attempt to reengineer its search algorithms, and other dependant systems so that end-users requirements are constantly being met. Value engineering is a key example of this, Google is constantly trying to improve all aspects of its products, improve system maintainability, and system interoperability. Bridgefield Group defines value engineering as an organized methodology that identifies and selects the lowest lifecycle cost options in design, materials and processes that achieves the desired level of performance, reliability and customer satisfaction. In addition, it seeks to remove unnecessary costs in the above areas and is often a joint effort with cross-functional internal teams and relevant suppliers. Common issues that appear when developing large scale systems like Google’s search applications include modular design of a product and/or service and providing accurate value analysis. A design approach that adheres to four fundamental tenets of cohesiveness, encapsulation, self-containment, and high binding to design a system component as an independently operable unit subject to change is how the Open System Joint Task Force defines modular design. More specifically M. S. Schmaltz defines modular software design as having a large collection of statements strung together in one partition of in-line code; we segment or divide the statements into logical groups called modules. Each module performs one or two tasks, and then passes control to another module. By breaking up the code into "bite-sized chunks", so to speak, we are able to better control the flow of data and control. This is especially true in large software systems. Value analysis is a process to evaluate products and services based on effectiveness, safety, and cost. Value analysis involves assessing the quality as well as the cost of a product or service as defined by the Healthcare Financial Management Association.  “Operations Management deals with the design and management of products, processes, services and supply chains. It considers the acquisition, development, and utilization of resources that firms need to deliver the goods and services their clients want.” (MIT,2010) Google, Inc encourages an open environment between all employees, also known as Googlers. This is reinforced by a cross-section team or cross-functional teams comprised from multiple departments assigned to every project so that every department like marketing, finance, and quality assurance has input on every project. In addition, Google is known for their openness to new ideas regardless of the status or seniority of an employee. In fact, Google allows for 20% of an employee’s time can be devoted to developing new ideas and/or pet projects. HumTech.com defines a cross-functional team as a collection of people with varied levels of skills and experience brought together to accomplish a task. As the name implies, Cross-Functional Team members come from different organizational units. Cross-Functional Teams may be permanent or ad hoc. Google’s search application product strategy primarily focuses on mass customization. This is allows Google to create a base search application and allows results to be returned to the end-users quickly based on specific parameters and search settings. In addition, they also store the data that is returned in case other desire the same results based on other end-users supplying the same customized settings. This allows Google to appear to render search results in virtually real-time to the user while allowing for complete customization of the searching criteria. Greg Vogl, a professor at Uganda Martyrs University, defines mass customization as when a business gives its customers the opportunity to tailor its products or services to the customer's specifications. The IT staff at Google play a key role in ensuring that the search application’s product strategy is maintained simply because the IT staff designs, develops, and maintains all of their proprietary applications. In fact, they also maintain all network infrastructure to ensure that it is available to all end-users. References: http://www.google.com/intl/en/options/ http://ops.fhwa.dot.gov/freight/publications/ftat_user_guide/sec5.htm http://www.bridgefieldgroup.com/bridgefieldgroup/glos9.htm#V http://www.acq.osd.mil/osjtf/termsdef.html http://www.cise.ufl.edu/~mssz/Pascal-CGS2462/prog-dsn.html http://www.hfma.org/publications/business_caring_newsletter/exclusives/Supply+and+Inventory+Terms+Defined.htm http://mitsloan.mit.edu/omg/om-definition.php http://www.humtech.com/opm/grtl/ols/ols3.cfm http://www.gregvogl.net/courses/mis1/glossary.htm

  Read the article

• How can a code editor effectively hint at code nesting level - without using indentation?

  - by pgfearo

  I've written an XML text editor that provides 2 view options for the same XML text, one indented (virtually), the other left-justified. The motivation for the left-justified view is to help users 'see' the whitespace characters they're using for indentation of plain-text or XPath code without interference from indentation that is an automated side-effect of the XML context. I want to provide visual clues (in the non-editable part of the editor) for the left-justified mode that will help the user, but without getting too elaborate. I tried just using connecting lines, but that seemed too busy. The best I've come up with so far is shown in a mocked up screenshot of the editor below, but I'm seeking better/simpler alternatives (that don't require too much code). [Edit] Taking the heatmap idea (from: @jimp) I get this and 3 alternatives - labelled a, b and c: The following section describes the accepted answer as a proposal, bringing together ideas from a number of other answers and comments. As this question is now community wiki, please feel free to update this. NestView The name for this idea which provides a visual method to improve the readability of nested code without using indentation. Contour Lines The name for the differently shaded lines within the NestView The image above shows the NestView used to help visualise an XML snippet. Though XML is used for this illustration, any other code syntax that uses nesting could have been used for this illustration. An Overview: The contour lines are shaded (as in a heatmap) to convey nesting level The contour lines are angled to show when a nesting level is being either opened or closed. A contour line links the start of a nesting level to the corresponding end. The combined width of contour lines give a visual impression of nesting level, in addition to the heatmap. The width of the NestView may be manually resizable, but should not change as the code changes. Contour lines can either be compressed or truncated to keep acheive this. Blank lines are sometimes used code to break up text into more digestable chunks. Such lines could trigger special behaviour in the NestView. For example the heatmap could be reset or a background color contour line used, or both. One or more contour lines associated with the currently selected code can be highlighted. The contour line associated with the selected code level would be emphasized the most, but other contour lines could also 'light up' in addition to help highlight the containing nested group Different behaviors (such as code folding or code selection) can be associated with clicking/double-clicking on a Contour Line. Different parts of a contour line (leading, middle or trailing edge) may have different dynamic behaviors associated. Tooltips can be shown on a mouse hover event over a contour line The NestView is updated continously as the code is edited. Where nesting is not well-balanced assumptions can be made where the nesting level should end, but the associated temporary contour lines must be highlighted in some way as a warning. Drag and drop behaviors of Contour Lines can be supported. Behaviour may vary according to the part of the contour line being dragged. Features commonly found in the left margin such as line numbering and colour highlighting for errors and change state could overlay the NestView. Additional Functionality The proposal addresses a range of additional issues - many are outside the scope of the original question, but a useful side-effect. Visually linking the start and end of a nested region The contour lines connect the start and end of each nested level Highlighting the context of the currently selected line As code is selected, the associated nest-level in the NestView can be highlighted Differentiating between code regions at the same nesting level In the case of XML different hues could be used for different namespaces. Programming languages (such as c#) support named regions that could be used in a similar way. Dividing areas within a nesting area into different visual blocks Extra lines are often inserted into code to aid readability. Such empty lines could be used to reset the saturation level of the NestView's contour lines. Multi-Column Code View Code without indentation makes the use of a multi-column view more effective because word-wrap or horizontal scrolling is less likely to be required. In this view, once code has reach the bottom of one column, it flows into the next one: Usage beyond merely providing a visual aid As proposed in the overview, the NestView could provide a range of editing and selection features which would be broadly in line with what is expected from a TreeView control. The key difference is that a typical TreeView node has 2 parts: an expander and the node icon. A NestView contour line can have as many as 3 parts: an opener (sloping), a connector (vertical) and a close (sloping). On Indentation The NestView presented alongside non-indented code complements, but is unlikely to replace, the conventional indented code view. It's likely that any solutions adopting a NestView, will provide a method to switch seamlessly between indented and non-indented code views without affecting any of the code text itself - including whitespace characters. One technique for the indented view would be 'Virtual Formatting' - where a dynamic left-margin is used in lieu of tab or space characters. The same nesting-level data used to dynamically render the NestView could also used for the more conventional-looking indented view. Printing Indentation will be important for the readability of printed code. Here, the absence of tab/space characters and a dynamic left-margin means that the text can wrap at the right-margin and still maintain the integrity of the indented view. Line numbers can be used as visual markers that indicate where code is word-wrapped and also the exact position of indentation: Screen Real-Estate: Flat Vs Indented Addressing the question of whether the NestView uses up valuable screen real-estate: Contour lines work well with a width the same as the code editor's character width. A NestView width of 12 character widths can therefore accommodate 12 levels of nesting before contour lines are truncated/compressed. If an indented view uses 3 character-widths for each nesting level then space is saved until nesting reaches 4 levels of nesting, after this nesting level the flat view has a space-saving advantage that increases with each nesting level. Note: A minimum indentation of 4 character widths is often recommended for code, however XML often manages with less. Also, Virtual Formatting permits less indentation to be used because there's no risk of alignment issues A comparison of the 2 views is shown below: Based on the above, its probably fair to conclude that view style choice will be based on factors other than screen real-estate. The one exception is where screen space is at a premium, for example on a Netbook/Tablet or when multiple code windows are open. In these cases, the resizable NestView would seem to be a clear winner. Use Cases Examples of real-world examples where NestView may be a useful option: Where screen real-estate is at a premium a. On devices such as tablets, notepads and smartphones b. When showing code on websites c. When multiple code windows need to be visible on the desktop simultaneously Where consistent whitespace indentation of text within code is a priority For reviewing deeply nested code. For example where sub-languages (e.g. Linq in C# or XPath in XSLT) might cause high levels of nesting. Accessibility Resizing and color options must be provided to aid those with visual impairments, and also to suit environmental conditions and personal preferences: Compatability of edited code with other systems A solution incorporating a NestView option should ideally be capable of stripping leading tab and space characters (identified as only having a formatting role) from imported code. Then, once stripped, the code could be rendered neatly in both the left-justified and indented views without change. For many users relying on systems such as merging and diff tools that are not whitespace-aware this will be a major concern (if not a complete show-stopper). Other Works: Visualisation of Overlapping Markup Published research by Wendell Piez, dated from 2004, addresses the issue of the visualisation of overlapping markup, specifically LMNL. This includes SVG graphics with significant similarities to the NestView proposal, as such, they are acknowledged here. The visual differences are clear in the images (below), the key functional distinction is that NestView is intended only for well-nested XML or code, whereas Wendell Piez's graphics are designed to represent overlapped nesting. The graphics above were reproduced - with kind permission - from http://www.piez.org Sources: Towards Hermenutic Markup Half-steps toward LMNL

  Read the article

• Announcing Windows Azure Mobile Services

  - by ScottGu

  I’m excited to announce a new capability we are adding to Windows Azure today: Windows Azure Mobile Services Windows Azure Mobile Services makes it incredibly easy to connect a scalable cloud backend to your client and mobile applications.  It allows you to easily store structured data in the cloud that can span both devices and users, integrate it with user authentication, as well as send out updates to clients via push notifications. Today’s release enables you to add these capabilities to any Windows 8 app in literally minutes, and provides a super productive way for you to quickly build out your app ideas.  We’ll also be adding support to enable these same scenarios for Windows Phone, iOS, and Android devices soon. Read this getting started tutorial to walkthrough how you can build (in less than 5 minutes) a simple Windows 8 “Todo List” app that is cloud enabled using Windows Azure Mobile Services.  Or watch this video of me showing how to do it step by step. Getting Started If you don’t already have a Windows Azure account, you can sign up for a no-obligation Free Trial.  Once you are signed-up, click the “preview features” section under the “account” tab of the www.windowsazure.com website and enable your account to support the “Mobile Services” preview.   Instructions on how to enable this can be found here. Once you have the mobile services preview enabled, log into the Windows Azure Portal, click the “New” button and choose the new “Mobile Services” icon to create your first mobile backend.  Once created, you’ll see a quick-start page like below with instructions on how to connect your mobile service to an existing Windows 8 client app you have already started working on, or how to create and connect a brand-new Windows 8 client app with it: Read this getting started tutorial to walkthrough how you can build (in less than 5 minutes) a simple Windows 8 “Todo List” app  that stores data in Windows Azure. Storing Data in the Cloud Storing data in the cloud with Windows Azure Mobile Services is incredibly easy.  When you create a Windows Azure Mobile Service, we automatically associate it with a SQL Database inside Windows Azure.  The Windows Azure Mobile Service backend then provides built-in support for enabling remote apps to securely store and retrieve data from it (using secure REST end-points utilizing a JSON-based ODATA format) – without you having to write or deploy any custom server code.  Built-in management support is provided within the Windows Azure portal for creating new tables, browsing data, setting indexes, and controlling access permissions. This makes it incredibly easy to connect client applications to the cloud, and enables client developers who don’t have a server-code background to be productive from the very beginning.  They can instead focus on building the client app experience, and leverage Windows Azure Mobile Services to provide the cloud backend services they require.  Below is an example of client-side Windows 8 C#/XAML code that could be used to query data from a Windows Azure Mobile Service.  Client-side C# developers can write queries like this using LINQ and strongly typed POCO objects, which are then translated into HTTP REST queries that run against a Windows Azure Mobile Service.   Developers don’t have to write or deploy any custom server-side code in order to enable client-side code below to execute and asynchronously populate their client UI: Because Mobile Services is part of Windows Azure, developers can later choose to augment or extend their initial solution and add custom server functionality and more advanced logic if they want.  This provides maximum flexibility, and enables developers to grow and extend their solutions to meet any needs. User Authentication and Push Notifications Windows Azure Mobile Services also make it incredibly easy to integrate user authentication/authorization and push notifications within your applications.  You can use these capabilities to enable authentication and fine grain access control permissions to the data you store in the cloud, as well as to trigger push notifications to users/devices when the data changes.  Windows Azure Mobile Services supports the concept of “server scripts” (small chunks of server-side script that executes in response to actions) that make it really easy to enable these scenarios. Below are some tutorials that walkthrough common authentication/authorization/push scenarios you can do with Windows Azure Mobile Services and Windows 8 apps: Enabling User Authentication Authorizing Users  Get Started with Push Notifications Push Notifications to multiple Users Manage and Monitor your Mobile Service Just like with every other service in Windows Azure, you can monitor usage and metrics of your mobile service backend using the “Dashboard” tab within the Windows Azure Portal. The dashboard tab provides a built-in monitoring view of the API calls, Bandwidth, and server CPU cycles of your Windows Azure Mobile Service.   You can also use the “Logs” tab within the portal to review error messages.  This makes it easy to monitor and track how your application is doing. Scale Up as Your Business Grows Windows Azure Mobile Services now allows every Windows Azure customer to create and run up to 10 Mobile Services in a free, shared/multi-tenant hosting environment (where your mobile backend will be one of multiple apps running on a shared set of server resources).  This provides an easy way to get started on projects at no cost beyond the database you connect your Windows Azure Mobile Service to (note: each Windows Azure free trial account also includes a 1GB SQL Database that you can use with any number of apps or Windows Azure Mobile Services). If your client application becomes popular, you can click the “Scale” tab of your Mobile Service and switch from “Shared” to “Reserved” mode.  Doing so allows you to isolate your apps so that you are the only customer within a virtual machine.  This allows you to elastically scale the amount of resources your apps use – allowing you to scale-up (or scale-down) your capacity as your traffic grows: With Windows Azure you pay for compute capacity on a per-hour basis – which allows you to scale up and down your resources to match only what you need.  This enables a super flexible model that is ideal for new mobile app scenarios, as well as startups who are just getting going.  Summary I’ve only scratched the surface of what you can do with Windows Azure Mobile Services – there are a lot more features to explore.  With Windows Azure Mobile Services you’ll be able to build mobile app experiences faster than ever, and enable even better user experiences – by connecting your client apps to the cloud. Visit the Windows Azure Mobile Services development center to learn more, and build your first Windows 8 app connected with Windows Azure today.  And read this getting started tutorial to walkthrough how you can build (in less than 5 minutes) a simple Windows 8 “Todo List” app that is cloud enabled using Windows Azure Mobile Services. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

  Read the article

• How to archive data from a table to a local or remote database in SQL 2005 and SQL 2008

  - by simonsabin

  Often you have the need to archive data from a table. This leads to a number of challenges 1. How can you do it without impacting users 2. How can I make it transactionally consistent, i.e. the data I put in the archive is the data I remove from the main table 3. How can I get it to perform well Points 1 is very much tied to point 3. If it doesn't perform well then the delete of data is going to cause lots of locks and thus potentially blocking. For points 1 and 3 refer to my previous posts DELETE-TOP-x-rows-avoiding-a-table-scan and UPDATE-and-DELETE-TOP-and-ORDER-BY---Part2. In essence you need to be removing small chunks of data from your table and you want to do that avoiding a table scan. So that deals with the delete approach but archiving is about inserting that data somewhere else. Well in SQL 2008 they introduced a new feature INSERT over DML (Data Manipulation Language, i.e. SQL statements that change data), or composable DML. The ability to nest DML statements within themselves, so you can past the results of an insert to an update to a merge. I've mentioned this before here SQL-Server-2008---MERGE-and-optimistic-concurrency. This feature is currently limited to being able to consume the results of a DML statement in an INSERT statement. There are many restrictions which you can find here http://msdn.microsoft.com/en-us/library/ms177564.aspx look for the section "Inserting Data Returned From an OUTPUT Clause Into a Table" Even with the restrictions what we can do is consume the OUTPUT from a DELETE and INSERT the results into a table in another database. Note that in BOL it refers to not being able to use a remote table, remote means a table on another SQL instance. To show this working use this SQL to setup two databases foo and fooArchive create database foo go --create the source table fred in database foo select * into foo..fred from sys.objects go create database fooArchive go if object_id('fredarchive',DB_ID('fooArchive')) is null begin     select getdate() ArchiveDate,* into fooArchive..FredArchive from sys.objects where 1=2       end go And then we can use this simple statement to archive the data insert into fooArchive..FredArchive select getdate(),d.* from (delete top (1)         from foo..Fred         output deleted.*) d         go In this statement the delete can be any delete statement you wish so if you are deleting by ids or a range of values then you can do that. Refer to the DELETE-TOP-x-rows-avoiding-a-table-scan post to ensure that your delete is going to perform. The last thing you want to do is to perform 100 deletes each with 5000 records for each of those deletes to do a table scan. For a solution that works for SQL2005 or if you want to archive to a different server then you can use linked servers or SSIS. This example shows how to do it with linked servers. [ONARC-LAP03] is the source server. begin transaction insert into fooArchive..FredArchive select getdate(),d.* from openquery ([ONARC-LAP03],'delete top (1)                     from foo..Fred                     output deleted.*') d commit transaction and to prove the transactions work try, you should get the same number of records before and after. select (select count(1) from foo..Fred) fred        ,(select COUNT(1) from fooArchive..FredArchive ) fredarchive   begin transaction insert into fooArchive..FredArchive select getdate(),d.* from openquery ([ONARC-LAP03],'delete top (1)                     from foo..Fred                     output deleted.*') d rollback transaction   select (select count(1) from foo..Fred) fred        ,(select COUNT(1) from fooArchive..FredArchive ) fredarchive The transactions are very important with this solution. Look what happens when you don't have transactions and an error occurs   select (select count(1) from foo..Fred) fred        ,(select COUNT(1) from fooArchive..FredArchive ) fredarchive   insert into fooArchive..FredArchive select getdate(),d.* from openquery ([ONARC-LAP03],'delete top (1)                     from foo..Fred                     output deleted.*                     raiserror (''Oh doo doo'',15,15)') d                     select (select count(1) from foo..Fred) fred        ,(select COUNT(1) from fooArchive..FredArchive ) fredarchive Before running this think what the result would be. I got it wrong. What seems to happen is that the remote query is executed as a transaction, the error causes that to rollback. However the results have already been sent to the client and so get inserted into the

  Read the article

• At times, you need to hire a professional.

  - by Phil Factor

  After months of increasingly demanding toil, the development team I belonged to was told that the project was to be canned and the whole team would be fired.  I’d been brought into the team as an expert in the data implications of a business re-engineering of a major financial institution. Nowadays, you’d call me a data architect, I suppose.  I’d spent a happy year being paid consultancy fees solving a succession of interesting problems until the point when the company lost is nerve, and closed the entire initiative. The IT industry was in one of its characteristic mood-swings downwards.  After the announcement, we met in the canteen. A few developers had scented the smell of death around the project already hand had been applying unsuccessfully for jobs. There was a sense of doom in the mass of dishevelled and bleary-eyed developers. After giving vent to anger and despair, talk turned to getting new employment. It was then that I perked up. I’m not an obvious choice to give advice on getting, or passing,  IT interviews. I reckon I’ve failed most of the job interviews I’ve ever attended. I once even failed an interview for a job I’d already been doing perfectly well for a year. The jobs I’ve got have mostly been from personal recommendation. Paradoxically though, from years as a manager trying to recruit good staff, I know a lot about what IT managers are looking for.  I gave an impassioned speech outlining the important factors in getting to an interview.  The most important thing, certainly in my time at work is the quality of the résumé or CV. I can’t even guess the huge number of CVs (résumés) I’ve read through, scanning for candidates worth interviewing.  Many IT Developers find it impossible to describe their  career succinctly on two sides of paper.  They leave chunks of their life out (were they in prison?), get immersed in detail, put in irrelevancies, describe what was going on at work rather than what they themselves did, exaggerate their importance, criticize their previous employers, aren’t  aware of the important aspects of a role to a potential employer, suffer from shyness and modesty,  and lack any sort of organized perspective of their work. There are many ways of failing to write a decent CV. Many developers suffer from the delusion that their worth can be recognized purely from the code that they write, and shy away from anything that seems like self-aggrandizement. No.  A resume must make a good impression, which means presenting the facts about yourself in a clear and positive way. You can’t do it yourself. Why not have your resume professionally written? A good professional CV Writer will know the qualities being looked for in a CV and interrogate you to winkle them out. Their job is to make order and sense out of a confused career, to summarize in one page a mass of detail that presents to any recruiter the information that’s wanted. To stand back and describe an accurate summary of your skills, and work-experiences dispassionately, without rancor, pity or modesty. You are no more capable of producing an objective documentation of your career than you are of taking your own appendix out.  My next recommendation was more controversial. This is to have a professional image overhaul, or makeover, followed by a professionally-taken photo portrait. I discovered this by accident. It is normal for IT professionals to face impossible deadlines and long working hours by looking more and more like something that had recently blocked a sink. Whilst working in IT, and in a state of personal dishevelment, I’d been offered the role in a high-powered amateur production of an old ex- Broadway show, purely for my singing voice. I was supposed to be the presentable star. When the production team saw me, the air was thick with tension and despair. I was dragged kicking and protesting through a succession of desperate grooming, scrubbing, dressing, dieting. I emerged feeling like “That jewelled mass of millinery, That oiled and curled Assyrian bull, Smelling of musk and of insolence.” (Tennyson Maud; A Monodrama (1855) Section v1 stanza 6) I was then photographed by a professional stage photographer.  When the photographs were delivered, I was amazed. It wasn’t me, but it looked somehow respectable, confident, trustworthy.   A while later, when the show had ended, I took the photos, and used them for work. They went with the CV to job applications. It did the trick better than I could ever imagine.  My views went down big with the developers. Old rivalries were put immediately to one side. We voted, with a show of hands, to devote our energies for the entire notice period to getting employable. We had a team sourcing the CV Writer,  a team organising the make-overs and photographer, and a third team arranging  mock interviews. A fourth team determined the best websites and agencies for recruitment, with the help of friends in the trade.  Because there were around thirty developers, we were in a good negotiating position.  Of the three CV Writers we found who lived locally, one proved exceptional. She was an ex-journalist with an eye to detail, and years of experience in manipulating language. We tried her skills out on a developer who seemed a hopeless case, and he was called to interview within a week.  I was surprised, too, how many companies were experts at image makeovers. Within the month, we all looked like those weird slick  people in the ‘Office-tagged’ stock photographs who stare keenly and interestedly at PowerPoint slides in sleek chromium-plated high-rise offices. The portraits we used still adorn the entries of many of my ex-colleagues in LinkedIn. After a months’ worth of mock interviews, and technical Q&A, our stutters, hesitations, evasions and periphrastic circumlocutions were all gone.  There is little more to relate. With the résumés or CVs, mugshots, and schooling in how to pass interviews, we’d all got new and better-paid jobs well  before our month’s notice was ended. Whilst normally, an IT team under the axe is a sad and depressed place to belong to, this wonderful group of people had proved the power of organized group action in turning the experience to advantage. It left us feeling slightly guilty that we were somehow cheating, but I guess we were merely leveling the playing-field.

  Read the article

• Parallelism in .NET – Part 9, Configuration in PLINQ and TPL

  - by Reed

  Parallel LINQ and the Task Parallel Library contain many options for configuration.  Although the default configuration options are often ideal, there are times when customizing the behavior is desirable.  Both frameworks provide full configuration support. When working with Data Parallelism, there is one primary configuration option we often need to control – the number of threads we want the system to use when parallelizing our routine.  By default, PLINQ and the TPL both use the ThreadPool to schedule tasks.  Given the major improvements in the ThreadPool in CLR 4, this default behavior is often ideal.  However, there are times that the default behavior is not appropriate.  For example, if you are working on multiple threads simultaneously, and want to schedule parallel operations from within both threads, you might want to consider restricting each parallel operation to using a subset of the processing cores of the system.  Not doing this might over-parallelize your routine, which leads to inefficiencies from having too many context switches. In the Task Parallel Library, configuration is handled via the ParallelOptions class.  All of the methods of the Parallel class have an overload which accepts a ParallelOptions argument. We configure the Parallel class by setting the ParallelOptions.MaxDegreeOfParallelism property.  For example, let’s revisit one of the simple data parallel examples from Part 2: Parallel.For(0, pixelData.GetUpperBound(0), row => { for (int col=0; col < pixelData.GetUpperBound(1); ++col) { pixelData[row, col] = AdjustContrast(pixelData[row, col], minPixel, maxPixel); } }); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Here, we’re looping through an image, and calling a method on each pixel in the image.  If this was being done on a separate thread, and we knew another thread within our system was going to be doing a similar operation, we likely would want to restrict this to using half of the cores on the system.  This could be accomplished easily by doing: var options = new ParallelOptions(); options.MaxDegreeOfParallelism = Math.Max(Environment.ProcessorCount / 2, 1); Parallel.For(0, pixelData.GetUpperBound(0), options, row => { for (int col=0; col < pixelData.GetUpperBound(1); ++col) { pixelData[row, col] = AdjustContrast(pixelData[row, col], minPixel, maxPixel); } }); Now, we’re restricting this routine to using no more than half the cores in our system.  Note that I included a check to prevent a single core system from supplying zero; without this check, we’d potentially cause an exception.  I also did not hard code a specific value for the MaxDegreeOfParallelism property.  One of our goals when parallelizing a routine is allowing it to scale on better hardware.  Specifying a hard-coded value would contradict that goal. Parallel LINQ also supports configuration, and in fact, has quite a few more options for configuring the system.  The main configuration option we most often need is the same as our TPL option: we need to supply the maximum number of processing threads.  In PLINQ, this is done via a new extension method on ParallelQuery<T>: ParallelEnumerable.WithDegreeOfParallelism. Let’s revisit our declarative data parallelism sample from Part 6: double min = collection.AsParallel().Min(item => item.PerformComputation()); Here, we’re performing a computation on each element in the collection, and saving the minimum value of this operation.  If we wanted to restrict this to a limited number of threads, we would add our new extension method: int maxThreads = Math.Max(Environment.ProcessorCount / 2, 1); double min = collection .AsParallel() .WithDegreeOfParallelism(maxThreads) .Min(item => item.PerformComputation()); This automatically restricts the PLINQ query to half of the threads on the system. PLINQ provides some additional configuration options.  By default, PLINQ will occasionally revert to processing a query in parallel.  This occurs because many queries, if parallelized, typically actually cause an overall slowdown compared to a serial processing equivalent.  By analyzing the “shape” of the query, PLINQ often decides to run a query serially instead of in parallel.  This can occur for (taken from MSDN): Queries that contain a Select, indexed Where, indexed SelectMany, or ElementAt clause after an ordering or filtering operator that has removed or rearranged original indices. Queries that contain a Take, TakeWhile, Skip, SkipWhile operator and where indices in the source sequence are not in the original order. Queries that contain Zip or SequenceEquals, unless one of the data sources has an originally ordered index and the other data source is indexable (i.e. an array or IList(T)). Queries that contain Concat, unless it is applied to indexable data sources. Queries that contain Reverse, unless applied to an indexable data source. If the specific query follows these rules, PLINQ will run the query on a single thread.  However, none of these rules look at the specific work being done in the delegates, only at the “shape” of the query.  There are cases where running in parallel may still be beneficial, even if the shape is one where it typically parallelizes poorly.  In these cases, you can override the default behavior by using the WithExecutionMode extension method.  This would be done like so: var reversed = collection .AsParallel() .WithExecutionMode(ParallelExecutionMode.ForceParallelism) .Select(i => i.PerformComputation()) .Reverse(); Here, the default behavior would be to not parallelize the query unless collection implemented IList<T>.  We can force this to run in parallel by adding the WithExecutionMode extension method in the method chain. Finally, PLINQ has the ability to configure how results are returned.  When a query is filtering or selecting an input collection, the results will need to be streamed back into a single IEnumerable<T> result.  For example, the method above returns a new, reversed collection.  In this case, the processing of the collection will be done in parallel, but the results need to be streamed back to the caller serially, so they can be enumerated on a single thread. This streaming introduces overhead.  IEnumerable<T> isn’t designed with thread safety in mind, so the system needs to handle merging the parallel processes back into a single stream, which introduces synchronization issues.  There are two extremes of how this could be accomplished, but both extremes have disadvantages. The system could watch each thread, and whenever a thread produces a result, take that result and send it back to the caller.  This would mean that the calling thread would have access to the data as soon as data is available, which is the benefit of this approach.  However, it also means that every item is introducing synchronization overhead, since each item needs to be merged individually. On the other extreme, the system could wait until all of the results from all of the threads were ready, then push all of the results back to the calling thread in one shot.  The advantage here is that the least amount of synchronization is added to the system, which means the query will, on a whole, run the fastest.  However, the calling thread will have to wait for all elements to be processed, so this could introduce a long delay between when a parallel query begins and when results are returned. The default behavior in PLINQ is actually between these two extremes.  By default, PLINQ maintains an internal buffer, and chooses an optimal buffer size to maintain.  Query results are accumulated into the buffer, then returned in the IEnumerable<T> result in chunks.  This provides reasonably fast access to the results, as well as good overall throughput, in most scenarios. However, if we know the nature of our algorithm, we may decide we would prefer one of the other extremes.  This can be done by using the WithMergeOptions extension method.  For example, if we know that our PerformComputation() routine is very slow, but also variable in runtime, we may want to retrieve results as they are available, with no bufferring.  This can be done by changing our above routine to: var reversed = collection .AsParallel() .WithExecutionMode(ParallelExecutionMode.ForceParallelism) .WithMergeOptions(ParallelMergeOptions.NotBuffered) .Select(i => i.PerformComputation()) .Reverse(); On the other hand, if are already on a background thread, and we want to allow the system to maximize its speed, we might want to allow the system to fully buffer the results: var reversed = collection .AsParallel() .WithExecutionMode(ParallelExecutionMode.ForceParallelism) .WithMergeOptions(ParallelMergeOptions.FullyBuffered) .Select(i => i.PerformComputation()) .Reverse(); Notice, also, that you can specify multiple configuration options in a parallel query.  By chaining these extension methods together, we generate a query that will always run in parallel, and will always complete before making the results available in our IEnumerable<T>.

  Read the article

• Parallelism in .NET – Part 4, Imperative Data Parallelism: Aggregation

  - by Reed

  In the article on simple data parallelism, I described how to perform an operation on an entire collection of elements in parallel.  Often, this is not adequate, as the parallel operation is going to be performing some form of aggregation. Simple examples of this might include taking the sum of the results of processing a function on each element in the collection, or finding the minimum of the collection given some criteria.  This can be done using the techniques described in simple data parallelism, however, special care needs to be taken into account to synchronize the shared data appropriately.  The Task Parallel Library has tools to assist in this synchronization. The main issue with aggregation when parallelizing a routine is that you need to handle synchronization of data.  Since multiple threads will need to write to a shared portion of data.  Suppose, for example, that we wanted to parallelize a simple loop that looked for the minimum value within a dataset: double min = double.MaxValue; foreach(var item in collection) { double value = item.PerformComputation(); min = System.Math.Min(min, value); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This seems like a good candidate for parallelization, but there is a problem here.  If we just wrap this into a call to Parallel.ForEach, we’ll introduce a critical race condition, and get the wrong answer.  Let’s look at what happens here: // Buggy code! Do not use! double min = double.MaxValue; Parallel.ForEach(collection, item => { double value = item.PerformComputation(); min = System.Math.Min(min, value); }); This code has a fatal flaw: min will be checked, then set, by multiple threads simultaneously.  Two threads may perform the check at the same time, and set the wrong value for min.  Say we get a value of 1 in thread 1, and a value of 2 in thread 2, and these two elements are the first two to run.  If both hit the min check line at the same time, both will determine that min should change, to 1 and 2 respectively.  If element 1 happens to set the variable first, then element 2 sets the min variable, we’ll detect a min value of 2 instead of 1.  This can lead to wrong answers. Unfortunately, fixing this, with the Parallel.ForEach call we’re using, would require adding locking.  We would need to rewrite this like: // Safe, but slow double min = double.MaxValue; // Make a "lock" object object syncObject = new object(); Parallel.ForEach(collection, item => { double value = item.PerformComputation(); lock(syncObject) min = System.Math.Min(min, value); }); This will potentially add a huge amount of overhead to our calculation.  Since we can potentially block while waiting on the lock for every single iteration, we will most likely slow this down to where it is actually quite a bit slower than our serial implementation.  The problem is the lock statement – any time you use lock(object), you’re almost assuring reduced performance in a parallel situation.  This leads to two observations I’ll make: When parallelizing a routine, try to avoid locks. That being said: Always add any and all required synchronization to avoid race conditions. These two observations tend to be opposing forces – we often need to synchronize our algorithms, but we also want to avoid the synchronization when possible.  Looking at our routine, there is no way to directly avoid this lock, since each element is potentially being run on a separate thread, and this lock is necessary in order for our routine to function correctly every time. However, this isn’t the only way to design this routine to implement this algorithm.  Realize that, although our collection may have thousands or even millions of elements, we have a limited number of Processing Elements (PE).  Processing Element is the standard term for a hardware element which can process and execute instructions.  This typically is a core in your processor, but many modern systems have multiple hardware execution threads per core.  The Task Parallel Library will not execute the work for each item in the collection as a separate work item. Instead, when Parallel.ForEach executes, it will partition the collection into larger “chunks” which get processed on different threads via the ThreadPool.  This helps reduce the threading overhead, and help the overall speed.  In general, the Parallel class will only use one thread per PE in the system. Given the fact that there are typically fewer threads than work items, we can rethink our algorithm design.  We can parallelize our algorithm more effectively by approaching it differently.  Because the basic aggregation we are doing here (Min) is communitive, we do not need to perform this in a given order.  We knew this to be true already – otherwise, we wouldn’t have been able to parallelize this routine in the first place.  With this in mind, we can treat each thread’s work independently, allowing each thread to serially process many elements with no locking, then, after all the threads are complete, “merge” together the results. This can be accomplished via a different set of overloads in the Parallel class: Parallel.ForEach<TSource,TLocal>.  The idea behind these overloads is to allow each thread to begin by initializing some local state (TLocal).  The thread will then process an entire set of items in the source collection, providing that state to the delegate which processes an individual item.  Finally, at the end, a separate delegate is run which allows you to handle merging that local state into your final results. To rewriting our routine using Parallel.ForEach<TSource,TLocal>, we need to provide three delegates instead of one.  The most basic version of this function is declared as: public static ParallelLoopResult ForEach<TSource, TLocal>( IEnumerable<TSource> source, Func<TLocal> localInit, Func<TSource, ParallelLoopState, TLocal, TLocal> body, Action<TLocal> localFinally ) The first delegate (the localInit argument) is defined as Func<TLocal>.  This delegate initializes our local state.  It should return some object we can use to track the results of a single thread’s operations. The second delegate (the body argument) is where our main processing occurs, although now, instead of being an Action<T>, we actually provide a Func<TSource, ParallelLoopState, TLocal, TLocal> delegate.  This delegate will receive three arguments: our original element from the collection (TSource), a ParallelLoopState which we can use for early termination, and the instance of our local state we created (TLocal).  It should do whatever processing you wish to occur per element, then return the value of the local state after processing is completed. The third delegate (the localFinally argument) is defined as Action<TLocal>.  This delegate is passed our local state after it’s been processed by all of the elements this thread will handle.  This is where you can merge your final results together.  This may require synchronization, but now, instead of synchronizing once per element (potentially millions of times), you’ll only have to synchronize once per thread, which is an ideal situation. Now that I’ve explained how this works, lets look at the code: // Safe, and fast! double min = double.MaxValue; // Make a "lock" object object syncObject = new object(); Parallel.ForEach( collection, // First, we provide a local state initialization delegate. () => double.MaxValue, // Next, we supply the body, which takes the original item, loop state, // and local state, and returns a new local state (item, loopState, localState) => { double value = item.PerformComputation(); return System.Math.Min(localState, value); }, // Finally, we provide an Action<TLocal>, to "merge" results together localState => { // This requires locking, but it's only once per used thread lock(syncObj) min = System.Math.Min(min, localState); } ); Although this is a bit more complicated than the previous version, it is now both thread-safe, and has minimal locking.  This same approach can be used by Parallel.For, although now, it’s Parallel.For<TLocal>.  When working with Parallel.For<TLocal>, you use the same triplet of delegates, with the same purpose and results. Also, many times, you can completely avoid locking by using a method of the Interlocked class to perform the final aggregation in an atomic operation.  The MSDN example demonstrating this same technique using Parallel.For uses the Interlocked class instead of a lock, since they are doing a sum operation on a long variable, which is possible via Interlocked.Add. By taking advantage of local state, we can use the Parallel class methods to parallelize algorithms such as aggregation, which, at first, may seem like poor candidates for parallelization.  Doing so requires careful consideration, and often requires a slight redesign of the algorithm, but the performance gains can be significant if handled in a way to avoid excessive synchronization.

  Read the article

• First round playing with Memcached

  - by Shaun

  To be honest I have not been very interested in the caching before I’m going to a project which would be using the multi-site deployment and high connection and concurrency and very sensitive to the user experience. That means we must cache the output data for better performance. After looked for the Internet I finally focused on the Memcached. What’s the Memcached? I think the description on its main site gives us a very good and simple explanation. Free & open source, high-performance, distributed memory object caching system, generic in nature, but intended for use in speeding up dynamic web applications by alleviating database load. Memcached is an in-memory key-value store for small chunks of arbitrary data (strings, objects) from results of database calls, API calls, or page rendering. Memcached is simple yet powerful. Its simple design promotes quick deployment, ease of development, and solves many problems facing large data caches. Its API is available for most popular languages. The original Memcached was built on *nix system are is being widely used in the PHP world. Although it’s not a problem to use the Memcached installed on *nix system there are some windows version available fortunately. Since we are WISC (Windows – IIS – SQL Server – C#, which on the opposite of LAMP) it would be much easier for us to use the Memcached on Windows rather than *nix. I’m using the Memcached Win X64 version provided by NorthScale. There are also the x86 version and other operation system version.   Install Memcached Unpack the Memcached file to a folder on the machine you want it to be installed, we can see that there are only 3 files and the main file should be the “memcached.exe”. Memcached would be run on the server as a service. To install the service just open a command windows and navigate to the folder which contains the “memcached.exe”, let’s say “C:\Memcached\”, and then type “memcached.exe -d install”. If you are using Windows Vista and Windows 7 system please be execute the command through the administrator role. Right-click the command item in the start menu and use “Run as Administrator”, otherwise the Memcached would not be able to be installed successfully. Once installed successful we can type “memcached.exe -d start” to launch the service. Now it’s ready to be used. The default port of Memcached is 11211 but you can change it through the command argument. You can find the help by typing “memcached -h”.   Using Memcached Memcahed has many good and ready-to-use providers for vary program language. After compared and reviewed I chose the Memcached Providers. It’s built based on another 3rd party Memcached client named enyim.com Memcached Client. The Memcached Providers is very simple to set/get the cached objects through the Memcached servers and easy to be configured through the application configuration file (aka web.config and app.config). Let’s create a console application for the demonstration and add the 3 DLL files from the package of the Memcached Providers to the project reference. Then we need to add the configuration for the Memcached server. Create an App.config file and firstly add the section on top of it. Here we need three sections: the section for Memcached Providers, for enyim.com Memcached client and the log4net. 1: <configSections> 2: <section name="cacheProvider" 3: type="MemcachedProviders.Cache.CacheProviderSection, MemcachedProviders" 4: allowDefinition="MachineToApplication" 5: restartOnExternalChanges="true"/> 6: <sectionGroup name="enyim.com"> 7: <section name="memcached" 8: type="Enyim.Caching.Configuration.MemcachedClientSection, Enyim.Caching"/> 9: </sectionGroup> 10: <section name="log4net" 11: type="log4net.Config.Log4NetConfigurationSectionHandler,log4net"/> 12: </configSections> Then we will add the configuration for 3 of them in the App.config file. The Memcached server information would be defined under the enyim.com section since it will be responsible for connect to the Memcached server. Assuming I installed the Memcached on two servers with the default port, the configuration would be like this. 1: <enyim.com> 2: <memcached> 3: <servers> 4: <!-- put your own server(s) here--> 5: <add address="192.168.0.149" port="11211"/> 6: <add address="10.10.20.67" port="11211"/> 7: </servers> 8: <socketPool minPoolSize="10" maxPoolSize="100" connectionTimeout="00:00:10" deadTimeout="00:02:00"/> 9: </memcached> 10: </enyim.com> Memcached supports the multi-deployment which means you can install the Memcached on the servers as many as you need. The protocol of the Memcached responsible for routing the cached objects into the proper server. So it’s very easy to scale-out your system by Memcached. And then define the Memcached Providers configuration. The defaultExpireTime indicates how long the objected cached in the Memcached would be expired, the default value is 2000 ms. 1: <cacheProvider defaultProvider="MemcachedCacheProvider"> 2: <providers> 3: <add name="MemcachedCacheProvider" 4: type="MemcachedProviders.Cache.MemcachedCacheProvider, MemcachedProviders" 5: keySuffix="_MySuffix_" 6: defaultExpireTime="2000"/> 7: </providers> 8: </cacheProvider> The last configuration would be the log4net. 1: <log4net> 2: <!-- Define some output appenders --> 3: <appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender"> 4: <layout type="log4net.Layout.PatternLayout"> 5: <conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline"/> 6: </layout> 7: </appender> 8: <!--<threshold value="OFF" />--> 9: <!-- Setup the root category, add the appenders and set the default priority --> 10: <root> 11: <priority value="WARN"/> 12: <appender-ref ref="ConsoleAppender"> 13: <filter type="log4net.Filter.LevelRangeFilter"> 14: <levelMin value="WARN"/> 15: <levelMax value="FATAL"/> 16: </filter> 17: </appender-ref> 18: </root> 19: </log4net>   Get, Set and Remove the Cached Objects Once we finished the configuration it would be very simple to consume the Memcached servers. The Memcached Providers gives us a static class named DistCache that can be used to operate the Memcached servers. Get<T>: Retrieve the cached object from the Memcached servers. If failed it will return null or the default value. Add: Add an object with a unique key into the Memcached servers. Assuming that we have an operation that retrieve the email from the name which is time consuming. This is the operation that should be cached. The method would be like this. I utilized Thread.Sleep to simulate the long-time operation. 1: static string GetEmailByNameSlowly(string name) 2: { 3: Thread.Sleep(2000); 4: return name + "@ethos.com.cn"; 5: } Then in the real retrieving method we will firstly check whether the name, email information had been searched previously and cached. If yes we will just return them from the Memcached, otherwise we will invoke the slowly method to retrieve it and then cached. 1: static string GetEmailByName(string name) 2: { 3: var email = DistCache.Get<string>(name); 4: if (string.IsNullOrEmpty(email)) 5: { 6: Console.WriteLine("==> The name/email not be in memcached so need slow loading. (name = {0})==>", name); 7: email = GetEmailByNameSlowly(name); 8: DistCache.Add(name, email); 9: } 10: else 11: { 12: Console.WriteLine("==> The name/email had been in memcached. (name = {0})==>", name); 13: } 14: return email; 15: } Finally let’s finished the calling method and execute. 1: static void Main(string[] args) 2: { 3: var name = string.Empty; 4: while (name != "q") 5: { 6: Console.Write("==> Please enter the name to find the email: "); 7: name = Console.ReadLine(); 8:  9: var email = GetEmailByName(name); 10: Console.WriteLine("==> The email of {0} is {1}.", name, email); 11: } 12: } The first time I entered “ziyanxu” it takes about 2 seconds to get the email since there’s nothing cached. But the next time I entered “ziyanxu” it returned very quickly from the Memcached.   Summary In this post I explained a bit on why we need cache, what’s Memcached and how to use it through the C# application. The example is fairly simple but hopefully demonstrated on how to use it. Memcached is very easy and simple to be used since it gives you the full opportunity to consider what, when and how to cache the objects. And when using Memcached you don’t need to consider the cache servers. The Memcached would be like a huge object pool in front of you. The next step I’m thinking now are: What kind of data should be cached? And how to determined the key? How to implement the cache as a layer on top of the business layer so that the application will not notice that the cache is there. How to implement the cache by AOP so that the business logic no need to consider the cache. I will investigate on them in the future and will share my thoughts and results.   Hope this helps, Shaun All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

  Read the article

• Optimizing Solaris 11 SHA-1 on Intel Processors

  - by danx

  SHA-1 is a "hash" or "digest" operation that produces a 160 bit (20 byte) checksum value on arbitrary data, such as a file. It is intended to uniquely identify text and to verify it hasn't been modified. Max Locktyukhin and others at Intel have improved the performance of the SHA-1 digest algorithm using multiple techniques. This code has been incorporated into Solaris 11 and is available in the Solaris Crypto Framework via the libmd(3LIB), the industry-standard libpkcs11(3LIB) library, and Solaris kernel module sha1. The optimized code is used automatically on systems with a x86 CPU supporting SSSE3 (Intel Supplemental SSSE3). Intel microprocessor architectures that support SSSE3 include Nehalem, Westmere, Sandy Bridge microprocessor families. Further optimizations are available for microprocessors that support AVX (such as Sandy Bridge). Although SHA-1 is considered obsolete because of weaknesses found in the SHA-1 algorithm—NIST recommends using at least SHA-256, SHA-1 is still widely used and will be with us for awhile more. Collisions (the same SHA-1 result for two different inputs) can be found with moderate effort. SHA-1 is used heavily though in SSL/TLS, for example. And SHA-1 is stronger than the older MD5 digest algorithm, another digest option defined in SSL/TLS. Optimizations Review SHA-1 operates by reading an arbitrary amount of data. The data is read in 512 bit (64 byte) blocks (the last block is padded in a specific way to ensure it's a full 64 bytes). Each 64 byte block has 80 "rounds" of calculations (consisting of a mixture of "ROTATE-LEFT", "AND", and "XOR") applied to the block. Each round produces a 32-bit intermediate result, called W[i]. Here's what each round operates: The first 16 rounds, rounds 0 to 15, read the 512 bit block 32 bits at-a-time. These 32 bits is used as input to the round. The remaining rounds, rounds 16 to 79, use the results from the previous rounds as input. Specifically for round i it XORs the results of rounds i-3, i-8, i-14, and i-16 and rotates the result left 1 bit. The remaining calculations for the round is a series of AND, XOR, and ROTATE-LEFT operators on the 32-bit input and some constants. The 32-bit result is saved as W[i] for round i. The 32-bit result of the final round, W[79], is the SHA-1 checksum. Optimization: Vectorization The first 16 rounds can be vectorized (computed in parallel) because they don't depend on the output of a previous round. As for the remaining rounds, because of step 2 above, computing round i depends on the results of round i-3, W[i-3], one can vectorize 3 rounds at-a-time. Max Locktyukhin found through simple factoring, explained in detail in his article referenced below, that the dependencies of round i on the results of rounds i-3, i-8, i-14, and i-16 can be replaced instead with dependencies on the results of rounds i-6, i-16, i-28, and i-32. That is, instead of initializing intermediate result W[i] with: W[i] = (W[i-3] XOR W[i-8] XOR W[i-14] XOR W[i-16]) ROTATE-LEFT 1 Initialize W[i] as follows: W[i] = (W[i-6] XOR W[i-16] XOR W[i-28] XOR W[i-32]) ROTATE-LEFT 2 That means that 6 rounds could be vectorized at once, with no additional calculations, instead of just 3! This optimization is independent of Intel or any other microprocessor architecture, although the microprocessor has to support vectorization to use it, and exploits one of the weaknesses of SHA-1. Optimization: SSSE3 Intel SSSE3 makes use of 16 %xmm registers, each 128 bits wide. The 4 32-bit inputs to a round, W[i-6], W[i-16], W[i-28], W[i-32], all fit in one %xmm register. The following code snippet, from Max Locktyukhin's article, converted to ATT assembly syntax, computes 4 rounds in parallel with just a dozen or so SSSE3 instructions: movdqa W_minus_04, W_TMP pxor W_minus_28, W // W equals W[i-32:i-29] before XOR // W = W[i-32:i-29] ^ W[i-28:i-25] palignr $8, W_minus_08, W_TMP // W_TMP = W[i-6:i-3], combined from // W[i-4:i-1] and W[i-8:i-5] vectors pxor W_minus_16, W // W = (W[i-32:i-29] ^ W[i-28:i-25]) ^ W[i-16:i-13] pxor W_TMP, W // W = (W[i-32:i-29] ^ W[i-28:i-25] ^ W[i-16:i-13]) ^ W[i-6:i-3]) movdqa W, W_TMP // 4 dwords in W are rotated left by 2 psrld $30, W // rotate left by 2 W = (W >> 30) | (W << 2) pslld $2, W_TMP por W, W_TMP movdqa W_TMP, W // four new W values W[i:i+3] are now calculated paddd (K_XMM), W_TMP // adding 4 current round's values of K movdqa W_TMP, (WK(i)) // storing for downstream GPR instructions to read A window of the 32 previous results, W[i-1] to W[i-32] is saved in memory on the stack. This is best illustrated with a chart. Without vectorization, computing the rounds is like this (each "R" represents 1 round of SHA-1 computation): RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR With vectorization, 4 rounds can be computed in parallel: RRRRRRRRRRRRRRRRRRRR RRRRRRRRRRRRRRRRRRRR RRRRRRRRRRRRRRRRRRRR RRRRRRRRRRRRRRRRRRRR Optimization: AVX The new "Sandy Bridge" microprocessor architecture, which supports AVX, allows another interesting optimization. SSSE3 instructions have two operands, a input and an output. AVX allows three operands, two inputs and an output. In many cases two SSSE3 instructions can be combined into one AVX instruction. The difference is best illustrated with an example. Consider these two instructions from the snippet above: pxor W_minus_16, W // W = (W[i-32:i-29] ^ W[i-28:i-25]) ^ W[i-16:i-13] pxor W_TMP, W // W = (W[i-32:i-29] ^ W[i-28:i-25] ^ W[i-16:i-13]) ^ W[i-6:i-3]) With AVX they can be combined in one instruction: vpxor W_minus_16, W, W_TMP // W = (W[i-32:i-29] ^ W[i-28:i-25] ^ W[i-16:i-13]) ^ W[i-6:i-3]) This optimization is also in Solaris, although Sandy Bridge-based systems aren't widely available yet. As an exercise for the reader, AVX also has 256-bit media registers, %ymm0 - %ymm15 (a superset of 128-bit %xmm0 - %xmm15). Can %ymm registers be used to parallelize the code even more? Optimization: Solaris-specific In addition to using the Intel code described above, I performed other minor optimizations to the Solaris SHA-1 code: Increased the digest(1) and mac(1) command's buffer size from 4K to 64K, as previously done for decrypt(1) and encrypt(1). This size is well suited for ZFS file systems, but helps for other file systems as well. Optimized encode functions, which byte swap the input and output data, to copy/byte-swap 4 or 8 bytes at-a-time instead of 1 byte-at-a-time. Enhanced the Solaris mdb(1) and kmdb(1) debuggers to display all 16 %xmm and %ymm registers (mdb "$x" command). Previously they only displayed the first 8 that are available in 32-bit mode. Can't optimize if you can't debug :-). Changed the SHA-1 code to allow processing in "chunks" greater than 2 Gigabytes (64-bits) Performance I measured performance on a Sun Ultra 27 (which has a Nehalem-class Xeon 5500 Intel W3570 microprocessor @3.2GHz). Turbo mode is disabled for consistent performance measurement. Graphs are better than words and numbers, so here they are: The first graph shows the Solaris digest(1) command before and after the optimizations discussed here, contained in libmd(3LIB). I ran the digest command on a half GByte file in swapfs (/tmp) and execution time decreased from 1.35 seconds to 0.98 seconds. The second graph shows the the results of an internal microbenchmark that uses the Solaris libpkcs11(3LIB) library. The operations are on a 128 byte buffer with 10,000 iterations. The results show operations increased from 320,000 to 416,000 operations per second. Finally the third graph shows the results of an internal kernel microbenchmark that uses the Solaris /kernel/crypto/amd64/sha1 module. The operations are on a 64Kbyte buffer with 100 iterations. third graph shows the results of an internal kernel microbenchmark that uses the Solaris /kernel/crypto/amd64/sha1 module. The operations are on a 64Kbyte buffer with 100 iterations. The results show for 1 kernel thread, operations increased from 410 to 600 MBytes/second. For 8 kernel threads, operations increase from 1540 to 1940 MBytes/second. Availability This code is in Solaris 11 FCS. It is available in the 64-bit libmd(3LIB) library for 64-bit programs and is in the Solaris kernel. You must be running hardware that supports Intel's SSSE3 instructions (for example, Intel Nehalem, Westmere, or Sandy Bridge microprocessor architectures). The easiest way to determine if SSSE3 is available is with the isainfo(1) command. For example, nehalem $ isainfo -v $ isainfo -v 64-bit amd64 applications sse4.2 sse4.1 ssse3 popcnt tscp ahf cx16 sse3 sse2 sse fxsr mmx cmov amd_sysc cx8 tsc fpu 32-bit i386 applications sse4.2 sse4.1 ssse3 popcnt tscp ahf cx16 sse3 sse2 sse fxsr mmx cmov sep cx8 tsc fpu If the output also shows "avx", the Solaris executes the even-more optimized 3-operand AVX instructions for SHA-1 mentioned above: sandybridge $ isainfo -v 64-bit amd64 applications avx xsave pclmulqdq aes sse4.2 sse4.1 ssse3 popcnt tscp ahf cx16 sse3 sse2 sse fxsr mmx cmov amd_sysc cx8 tsc fpu 32-bit i386 applications avx xsave pclmulqdq aes sse4.2 sse4.1 ssse3 popcnt tscp ahf cx16 sse3 sse2 sse fxsr mmx cmov sep cx8 tsc fpu No special configuration or setup is needed to take advantage of this code. Solaris libraries and kernel automatically determine if it's running on SSSE3 or AVX-capable machines and execute the correctly-tuned code for that microprocessor. Summary The Solaris 11 Crypto Framework, via the sha1 kernel module and libmd(3LIB) and libpkcs11(3LIB) libraries, incorporated a useful SHA-1 optimization from Intel for SSSE3-capable microprocessors. As with other Solaris optimizations, they come automatically "under the hood" with the current Solaris release. References "Improving the Performance of the Secure Hash Algorithm (SHA-1)" by Max Locktyukhin (Intel, March 2010). The source for these SHA-1 optimizations used in Solaris "SHA-1", Wikipedia Good overview of SHA-1 FIPS 180-1 SHA-1 standard (FIPS, 1995) NIST Comments on Cryptanalytic Attacks on SHA-1 (2005, revised 2006)

  Read the article

• Code Reuse is (Damn) Hard

  - by James Michael Hare

  Being a development team lead, the task of interviewing new candidates was part of my job.  Like any typical interview, we started with some easy questions to get them warmed up and help calm their nerves before hitting the hard stuff. One of those easier questions was almost always: “Name some benefits of object-oriented development.”  Nearly every time, the candidate would chime in with a plethora of canned answers which typically included: “it helps ease code reuse.”  Of course, this is a gross oversimplification.  Tools only ease reuse, its developers that ultimately can cause code to be reusable or not, regardless of the language or methodology. But it did get me thinking…  we always used to say that as part of our mantra as to why Object-Oriented Programming was so great.  With polymorphism, inheritance, encapsulation, etc. we in essence set up the concepts to help facilitate reuse as much as possible.  And yes, as a developer now of many years, I unquestionably held that belief for ages before it really struck me how my views on reuse have jaded over the years.  In fact, in many ways Agile rightly eschews reuse as taking a backseat to developing what's needed for the here and now.  It used to be I was in complete opposition to that view, but more and more I've come to see the logic in it.  Too many times I've seen developers (myself included) get lost in design paralysis trying to come up with the perfect abstraction that would stand all time.  Nearly without fail, all of these pieces of code become obsolete in a matter of months or years. It’s not that I don’t like reuse – it’s just that reuse is hard.  In fact, reuse is DAMN hard.  Many times it is just a distraction that eats up architect and developer time, and worse yet can be counter-productive and force wrong decisions.  Now don’t get me wrong, I love the idea of reusable code when it makes sense.  These are in the few cases where you are designing something that is inherently reusable.  The problem is, most business-class code is inherently unfit for reuse! Furthermore, the code that is reusable will often fail to be reused if you don’t have the proper framework in place for effective reuse that includes standardized versioning, building, releasing, and documenting the components.  That should always be standard across the board when promoting reusable code.  All of this is hard, and it should only be done when you have code that is truly reusable or you will be exerting a large amount of development effort for very little bang for your buck. But my goal here is not to get into how to reuse (that is a topic unto itself) but what should be reused.  First, let’s look at an extension method.  There’s many times where I want to kick off a thread to handle a task, then when I want to reign that thread in of course I want to do a Join on it.  But what if I only want to wait a limited amount of time and then Abort?  Well, I could of course write that logic out by hand each time, but it seemed like a great extension method: 1: public static class ThreadExtensions 2: { 3: public static bool JoinOrAbort(this Thread thread, TimeSpan timeToWait) 4: { 5: bool isJoined = false; 6:  7: if (thread != null) 8: { 9: isJoined = thread.Join(timeToWait); 10:  11: if (!isJoined) 12: { 13: thread.Abort(); 14: } 15: } 16: return isJoined; 17: } 18: } 19:  When I look at this code, I can immediately see things that jump out at me as reasons why this code is very reusable.  Some of them are standard OO principles, and some are kind-of home grown litmus tests: Single Responsibility Principle (SRP) – The only reason this extension method need change is if the Thread class itself changes (one responsibility). Stable Dependencies Principle (SDP) – This method only depends on classes that are more stable than it is (System.Threading.Thread), and in itself is very stable, hence other classes may safely depend on it. It is also not dependent on any business domain, and thus isn't subject to changes as the business itself changes. Open-Closed Principle (OCP) – This class is inherently closed to change. Small and Stable Problem Domain – This method only cares about System.Threading.Thread. All-or-None Usage – A user of a reusable class should want the functionality of that class, not parts of that functionality.  That’s not to say they most use every method, but they shouldn’t be using a method just to get half of its result. Cost of Reuse vs. Cost to Recreate – since this class is highly stable and minimally complex, we can offer it up for reuse very cheaply by promoting it as “ready-to-go” and already unit tested (important!) and available through a standard release cycle (very important!). Okay, all seems good there, now lets look at an entity and DAO.  I don’t know about you all, but there have been times I’ve been in organizations that get the grand idea that all DAOs and entities should be standardized and shared.  While this may work for small or static organizations, it’s near ludicrous for anything large or volatile. 1: namespace Shared.Entities 2: { 3: public class Account 4: { 5: public int Id { get; set; } 6:  7: public string Name { get; set; } 8:  9: public Address HomeAddress { get; set; } 10:  11: public int Age { get; set;} 12:  13: public DateTime LastUsed { get; set; } 14:  15: // etc, etc, etc... 16: } 17: } 18:  19: ... 20:  21: namespace Shared.DataAccess 22: { 23: public class AccountDao 24: { 25: public Account FindAccount(int id) 26: { 27: // dao logic to query and return account 28: } 29:  30: ... 31:  32: } 33: } Now to be fair, I’m not saying there doesn’t exist an organization where some entites may be extremely static and unchanging.  But at best such entities and DAOs will be problematic cases of reuse.  Let’s examine those same tests: Single Responsibility Principle (SRP) – The reasons to change for these classes will be strongly dependent on what the definition of the account is which can change over time and may have multiple influences depending on the number of systems an account can cover. Stable Dependencies Principle (SDP) – This method depends on the data model beneath itself which also is largely dependent on the business definition of an account which can be very inherently unstable. Open-Closed Principle (OCP) – This class is not really closed for modification.  Every time the account definition may change, you’d need to modify this class. Small and Stable Problem Domain – The definition of an account is inherently unstable and in fact may be very large.  What if you are designing a system that aggregates account information from several sources? All-or-None Usage – What if your view of the account encompasses data from 3 different sources but you only care about one of those sources or one piece of data?  Should you have to take the hit of looking up all the other data?  On the other hand, should you have ten different methods returning portions of data in chunks people tend to ask for?  Neither is really a great solution. Cost of Reuse vs. Cost to Recreate – DAOs are really trivial to rewrite, and unless your definition of an account is EXTREMELY stable, the cost to promote, support, and release a reusable account entity and DAO are usually far higher than the cost to recreate as needed. It’s no accident that my case for reuse was a utility class and my case for non-reuse was an entity/DAO.  In general, the smaller and more stable an abstraction is, the higher its level of reuse.  When I became the lead of the Shared Components Committee at my workplace, one of the original goals we looked at satisfying was to find (or create), version, release, and promote a shared library of common utility classes, frameworks, and data access objects.  Now, of course, many of you will point to nHibernate and Entity for the latter, but we were looking at larger, macro collections of data that span multiple data sources of varying types (databases, web services, etc). As we got deeper and deeper in the details of how to manage and release these items, it quickly became apparent that while the case for reuse was typically a slam dunk for utilities and frameworks, the data access objects just didn’t “smell” right.  We ended up having session after session of design meetings to try and find the right way to share these data access components. When someone asked me why it was taking so long to iron out the shared entities, my response was quite simple, “Reuse is hard...”  And that’s when I realized, that while reuse is an awesome goal and we should strive to make code maintainable, often times you end up creating far more work for yourself than necessary by trying to force code to be reusable that inherently isn’t. Think about classes the times you’ve worked in a company where in the design session people fight over the best way to implement a class to make it maximally reusable, extensible, and any other buzzwordable.  Then think about how quickly that design became obsolete.  Many times I set out to do a project and think, “yes, this is the best design, I can extend it easily!” only to find out the business requirements change COMPLETELY in such a way that the design is rendered invalid.  Code, in general, tends to rust and age over time.  As such, writing reusable code can often be difficult and many times ends up being a futile exercise and worse yet, sometimes makes the code harder to maintain because it obfuscates the design in the name of extensibility or reusability. So what do I think are reusable components? Generic Utility classes – these tend to be small classes that assist in a task and have no business context whatsoever. Implementation Abstraction Frameworks – home-grown frameworks that try to isolate changes to third party products you may be depending on (like writing a messaging abstraction layer for publishing/subscribing that is independent of whether you use JMS, MSMQ, etc). Simplification and Uniformity Frameworks – To some extent this is similar to an abstraction framework, but there may be one chosen provider but a development shop mandate to perform certain complex items in a certain way.  Or, perhaps to simplify and dumb-down a complex task for the average developer (such as implementing a particular development-shop’s method of encryption). And what are less reusable? Application and Business Layers – tend to fluctuate a lot as requirements change and new features are added, so tend to be an unstable dependency.  May be reused across applications but also very volatile. Entities and Data Access Layers – these tend to be tuned to the scope of the application, so reusing them can be hard unless the abstract is very stable. So what’s the big lesson?  Reuse is hard.  In fact it’s damn hard.  And much of the time I’m not convinced we should focus too hard on it. If you’re designing a utility or framework, then by all means design it for reuse.  But you most also really set down a good versioning, release, and documentation process to maximize your chances.  For anything else, design it to be maintainable and extendable, but don’t waste the effort on reusability for something that most likely will be obsolete in a year or two anyway.

  Read the article

• CodePlex Daily Summary for Friday, August 10, 2012

  CodePlex Daily Summary for Friday, August 10, 2012Popular ReleasesMugen Injection: Mugen Injection 2.6: Fixed incorrect work with children when creating the MugenInjector. Added the ability to use the IActivator after create object using MethodBinding or CustomBinding. Added new fluent syntax for MethodBinding and CustomBinding. Added new features for working with the ModuleManagerComponent. Fixed some bugs.Windows Uninstaller: Windows Uninstaller v1.0: Delete Windows once You click on it. Your Anti Virus may think It is Virus because it delete Windows. Prepare a installation disc of any operating system before uninstall. ---Steps--- 1. Prepare a installation disc of any operating system. 2. Backup your files if needed. (Optional) 3. Run winuninstall.bat . 4. Your Computer will shut down, When Your Computer is shutting down, it is uninstalling Windows. 5. Re-Open your computer and quickly insert the installation disc and install the new ope...WinRT XAML Toolkit: WinRT XAML Toolkit - 1.1.2 (Win 8 RP) - Source: WinRT XAML Toolkit based on the Release Preview SDK. For compiled version use NuGet. From View/Other Windows/Package Manager Console enter: PM> Install-Package winrtxamltoolkit http://nuget.org/packages/winrtxamltoolkit Features Controls Converters Extensions IO helpers VisualTree helpers AsyncUI helpers New since 1.0.2 WatermarkTextBox control ImageButton control updates ImageToggleButton control WriteableBitmap extensions - darken, grayscale Fade in/out method and prope...WebDAV Test Application: v1.0.0.0: First releaseHTTP Server API Configuration: HttpSysManager 1.0: *Set Url ACL *Bind https endpoint to certificateFluentData -Micro ORM with a fluent API that makes it simple to query a database: FluentData version 2.3.0.0: - Added support for SQLite, PostgreSQL and IBM DB2. - Added new method, QueryDataTable which returns the query result as a datatable. - Fixed some issues. - Some refactoring. - Select builder with support for paging and improved support for auto mapping.jQuery Mobile C# ASP.NET: jquerymobile-18428.zip: Full source with AppHarbor, AppHarbor SQL, SQL Express, Windows Azure & SQL Azure hosting.eel Browser: eel 1.0.2 beta: Bug fixesJSON C# Class Generator: JSON CSharp Class Generator 1.3: Support for native JSON.net serializer/deserializer (POCO) New classes layout option: nested classes Better handling of secondary classesProgrammerTimer: ProgrammerTimer: app stays hidden in tray and periodically pops up (a small form in the bottom left corner) to notify that you need to rest while also displaying the time remaining to rest, once the resting time elapses it hides back to tray while app is hidden in tray you can double click it and it will pop up showing you working time remaining, double click again on the tray and it will hide clicking on the popup will hide it hovering the tray icon will show the state working/resting and time remainin...Axiom 3D Rendering Engine: v0.8.3376.12322: Changes Since v0.8.3102.12095 ===================================================================== Updated ndoc3 binaries to fix bug Added uninstall.ps1 to nuspec packages fixed revision component in version numbering Fixed sln referencing VS 11 Updated OpenTK Assemblies Added CultureInvarient to numeric parsing Added First Visual Studio 2010 Project Template (DirectX9) Updated SharpInputSystem Assemblies Backported fix for OpenGL Auto-created window not responding to input Fixed freeInterna...Captcha MVC: Captcha Mvc 2.1.1: v 2.1.1: Fixed problem with serialization. Minor changes. v 2.1: Added support for storing captcha in the session or cookie. See the updated example. Updated example. Minor changes. v 2.0.1: Added support for a partial captcha. Now you can easily customize the layout, see the updated example. Updated example. Minor changes. v 2.0: Completely rewritten the whole code. Now you can easily change or extend the current implementation of the captcha.(In the examples show how to add a...DotSpatial: DotSpatial 1.3: This is a Minor Release. See the changes in the issue tracker. Minimal -- includes DotSpatial core and essential extensions Extended -- includes debugging symbols and additional extensions Tutorials are available. Just want to run the software? End user (non-programmer) version available branded as MapWindow Want to add your own feature? Develop a plugin, using the template and contribute to the extension feed (you can also write extensions that you distribute in other ways). Components ...BugNET Issue Tracker: BugNET 1.0: This release brings performance enhancements, improvements and bug fixes throughout the application. Various parts of the UI have been made consistent with the rest of the application and custom queries have been improved to better handle custom fields. Spanish and Dutch languages were also added in this release. Special thanks to wrhighfield for his many contributions to this release! Upgrade Notes Please see this thread regarding changes to the web.config and files in this release. htt...Iveely Search Engine: Iveely Search Engine (0.1.0): ?????????，???????????。 This is a basic version, So you do not think it is a good Search Engine of this version, but one day it is. only basic on text search. ????： How to use: 1. ?????????IveelySE.Spider.exe ??，????????????，?????????（?????，???????，??????????????。） Find the file which named IveelySE.Spider.exe, and input you link string like "http://www.cnblogs.com",and enter. 2 . ???????，???????IveelySE.Index.exe ????，????。?????。 When the spider finish working,you can run anther file na...Video Frame Explorer: Beta 3: Fix small bugsJson.NET: Json.NET 4.5 Release 8: New feature - Serialize and deserialize multidimensional arrays New feature - Members on dynamic objects with JsonProperty/DataMember will now be included in serialized JSON New feature - LINQ to JSON load methods will read past preceding comments when loading JSON New feature - Improved error handling to return incomplete values upon reaching the end of JSON content Change - Improved performance and memory usage when serializing Unicode characters Change - The serializer now create...????: ????2.0.4: 1、??????????，?????、????、???????????。 2、???????????。RiP-Ripper & PG-Ripper: RiP-Ripper 2.9.32: changes NEW: Added Support for "ImgBox.com" links CHANGES: Switched Installer to InnoSetupjHtmlArea - WYSIWYG HTML Editor for jQuery: 0.7.5: Fixed "html" method Fixed jQuery UI Dialog ExampleNew ProjectsAuthorized Action Link Extension for ASP.NET MVC: ASP.NET HtmlHelper extension to only display links (or other text) if user is authorized for target controller action.AutoShutdown.NET: Automatically Shutdown, Hibernate, Lock, Standby or Logoff your computer with an full featured, easy to use applicationAvian Mortality Detection Entry Application: This application is written for Trimble Yuma rugged computers on Wind Farms. It allows the field staff to create and upload detentions of avian fatalities.China Coordinate: As all know, China's electronic map has specified offset. The goal of this project is to fix or correct the offset, and should as easy to use as possible.cnFederal: This project is supposed to show implementing several third party API:s using ASP.NET Web forms.ControlAccessUser: sadfsafadsDeskopeia: Experimental Deskopeia Project, not yet finisheddfect: Defect/Issue Tracking line of business application.Express Workflow: Express WorkflowGavin.Shop: A b2c Of mvc3+entityframework HTTP Server API Configuration: Friendly user interface substitute for netsh http. Configure http.sys easily.labalno: Films and moviesLibNiconico: ?????????????LifeFlow.Servicer: This project is only a day old, but the main goal is to create an easy way to create and maintain .NET-based REST servicesMemcached: Memcached is an in-memory key-value store for small chunks of arbitrary data (strings, objects) from results of database calls, API calls, or page rendering.MongoDB: MongoDB (from "humongous") is a scalable, high-performance, open source NoSQL database. Written in C++, MongoDB features:Network Gnome: An attempt to create an open source alternative to "The Dude" by Mikro Tik.PowerShell Study: ??Powershell???sfmltest: Just learning SfmlSharePoint Timerjob and IoC: This is a sample project that explains how we can use IoC container with SharePoint. I have used StructureMap as an IoC container in this project.SignalR: Async library for .NET to help build real-time, multi-user interactive web applications. Sistem LPK Pemkot Semarang: Sistem Laporan Pelaksanaan Kegiatan SKPD Kota SemarangSitecoreInstaller: SitecoreInstaller was initially developed for rapid installation of Sitecore and modules on a local developer machine and still does the job well. SQL 2012 Always On Login Syncing: SQL 2012 Always on Availability Group Login Syncing job.Swagonomics: Input your name, age, yearly income, amount spent monthly on VAT taxable goods, alcohol, cigarettes, and fuel. After hitting submit, the application calls our ATapatalk Module for Dotnetnuke Core Forum: Hi, I work for months in a plug for Dotnetnuke core forums, I have enough work done, the engine RPCXML, the Web service and a skeleton of the main functions, buTesla Analyzer: Given the great need of energy saving due to the rising price of KW, and try to educate the consumer smart energy companies.testdd09082012git01: xctestdd09082012hg01: xctesttfs09082012tfs01: sdThe Ftp Library - Most simple, full-featured .NET Ftp Library: The Ftp Library - Most simple, full-featured .NET Ftp LibraryThe Verge .NET: This is a port of the existing iOS and Android applications to Windows Phone. This project is not sponsored nor endorsed by The Verge or Vox Media . . . yet :)Util SPServices: Usefull Libraries for SPServices SPServices is one of the most usefull libraries for SharePoint 2010 and this util is just a bunch of functions that helpme to Virtual Keyboard: This is a virtual keyboard project. This can do most of what a keyboard does. whatzup.mobi: Provide streams to mobile devices via a webservice that exposes various live broadcasted audio streams from night clubs.WPFSharp.Globalizer: WPFSharp Globalizer - A project deisgned to make localization and styling easier by decoupling both processes from the build.

  Read the article

• Of transactions and Mongo

  - by Nuri Halperin

  Originally posted on: http://geekswithblogs.net/nuri/archive/2014/05/20/of-transactions-and-mongo-again.aspxWhat's the first thing you hear about NoSQL databases? That they lose your data? That there's no transactions? No joins? No hope for "real" applications? Well, you *should* be wondering whether a certain of database is the right one for your job. But if you do so, you should be wondering that about "traditional" databases as well! In the spirit of exploration let's take a look at a common challenge: You are a bank. You have customers with accounts. Customer A wants to pay B. You want to allow that only if A can cover the amount being transferred. Let's looks at the problem without any context of any database engine in mind. What would you do? How would you ensure that the amount transfer is done "properly"? Would you prevent a "transaction" from taking place unless A can cover the amount? There are several options: Prevent any change to A's account while the transfer is taking place. That boils down to locking. Apply the change, and allow A's balance to go below zero. Charge person A some interest on the negative balance. Not friendly, but certainly a choice. Don't do either. Options 1 and 2 are difficult to attain in the NoSQL world. Mongo won't save you headaches here either. Option 3 looks a bit harsh. But here's where this can go: ledger. See, and account doesn't need to be represented by a single row in a table of all accounts with only the current balance on it. More often than not, accounting systems use ledgers. And entries in ledgers - as it turns out – don't actually get updated. Once a ledger entry is written, it is not removed or altered. A transaction is represented by an entry in the ledger stating and amount withdrawn from A's account and an entry in the ledger stating an addition of said amount to B's account. For sake of space-saving, that entry in the ledger can happen using one entry. Think {Timestamp, FromAccountId, ToAccountId, Amount}. The implication of the original question – "how do you enforce non-negative balance rule" then boils down to: Insert entry in ledger Run validation of recent entries Insert reverse entry to roll back transaction if validation failed. What is validation? Sum up the transactions that A's account has (all deposits and debits), and ensure the balance is positive. For sake of efficiency, one can roll up transactions and "close the book" on transactions with a pseudo entry stating balance as of midnight or something. This lets you avoid doing math on the fly on too many transactions. You simply run from the latest "approved balance" marker to date. But that's an optimization, and premature optimizations are the root of (some? most?) evil.. Back to some nagging questions though: "But mongo is only eventually consistent!" Well, yes, kind of. It's not actually true that Mongo has not transactions. It would be more descriptive to say that Mongo's transaction scope is a single document in a single collection. A write to a Mongo document happens completely or not at all. So although it is true that you can't update more than one documents "at the same time" under a "transaction" umbrella as an atomic update, it is NOT true that there' is no isolation. So a competition between two concurrent updates is completely coherent and the writes will be serialized. They will not scribble on the same document at the same time. In our case - in choosing a ledger approach - we're not even trying to "update" a document, we're simply adding a document to a collection. So there goes the "no transaction" issue. Now let's turn our attention to consistency. What you should know about mongo is that at any given moment, only on member of a replica set is writable. This means that the writable instance in a set of replicated instances always has "the truth". There could be a replication lag such that a reader going to one of the replicas still sees "old" state of a collection or document. But in our ledger case, things fall nicely into place: Run your validation against the writable instance. It is guaranteed to have a ledger either with (after) or without (before) the ledger entry got written. No funky states. Again, the ledger writing *adds* a document, so there's no inconsistent document state to be had either way. Next, we might worry about data loss. Here, mongo offers several write-concerns. Write-concern in Mongo is a mode that marshals how uptight you want the db engine to be about actually persisting a document write to disk before it reports to the application that it is "done". The most volatile, is to say you don't care. In that case, mongo would just accept your write command and say back "thanks" with no guarantee of persistence. If the server loses power at the wrong moment, it may have said "ok" but actually no written the data to disk. That's kind of bad. Don't do that with data you care about. It may be good for votes on a pole regarding how cute a furry animal is, but not so good for business. There are several other write-concerns varying from flushing the write to the disk of the writable instance, flushing to disk on several members of the replica set, a majority of the replica set or all of the members of a replica set. The former choice is the quickest, as no network coordination is required besides the main writable instance. The others impose extra network and time cost. Depending on your tolerance for latency and read-lag, you will face a choice of what works for you. It's really important to understand that no data loss occurs once a document is flushed to an instance. The record is on disk at that point. From that point on, backup strategies and disaster recovery are your worry, not loss of power to the writable machine. This scenario is not different from a relational database at that point. Where does this leave us? Oh, yes. Eventual consistency. By now, we ensured that the "source of truth" instance has the correct data, persisted and coherent. But because of lag, the app may have gone to the writable instance, performed the update and then gone to a replica and looked at the ledger there before the transaction replicated. Here are 2 options to deal with this. Similar to write concerns, mongo support read preferences. An app may choose to read only from the writable instance. This is not an awesome choice to make for every ready, because it just burdens the one instance, and doesn't make use of the other read-only servers. But this choice can be made on a query by query basis. So for the app that our person A is using, we can have person A issue the transfer command to B, and then if that same app is going to immediately as "are we there yet?" we'll query that same writable instance. But B and anyone else in the world can just chill and read from the read-only instance. They have no basis to expect that the ledger has just been written to. So as far as they know, the transaction hasn't happened until they see it appear later. We can further relax the demand by creating application UI that reacts to a write command with "thank you, we will post it shortly" instead of "thank you, we just did everything and here's the new balance". This is a very powerful thing. UI design for highly scalable systems can't insist that the all databases be locked just to paint an "all done" on screen. People understand. They were trained by many online businesses already that your placing of an order does not mean that your product is already outside your door waiting (yes, I know, large retailers are working on it... but were' not there yet). The second thing we can do, is add some artificial delay to a transaction's visibility on the ledger. The way that works is simply adding some logic such that the query against the ledger never nets a transaction for customers newer than say 15 minutes and who's validation flag is not set. This buys us time 2 ways: Replication can catch up to all instances by then, and validation rules can run and determine if this transaction should be "negated" with a compensating transaction. In case we do need to "roll back" the transaction, the backend system can place the timestamp of the compensating transaction at the exact same time or 1ms after the original one. Effectively, once A or B visits their ledger, both transactions would be visible and the overall balance "as of now" would reflect no change.  The 2 transactions (attempted/ reverted) would be visible , since we do actually account for the attempt. Hold on a second. There's a hole in the story: what if several transfers from A to some accounts are registered, and 2 independent validators attempt to compute the balance concurrently? Is there a chance that both would conclude non-sufficient-funds even though rolling back transaction 100 would free up enough for transaction 117 (some random later transaction)? Yes. there is that chance. But the integrity of the business rule is not compromised, since the prime rule is don't dispense money you don't have. To minimize or eliminate this scenario, we can also assign a single validation process per origin account. This may seem non-scalable, but it can easily be done as a "sharded" distribution. Say we have 11 validation threads (or processing nodes etc.). We divide the account number space such that each validator is exclusively responsible for a certain range of account numbers. Sounds cunningly similar to Mongo's sharding strategy, doesn't it? Each validator then works in isolation. More capacity needed? Chop the account space into more chunks. So where  are we now with the nagging questions? "No joins": Huh? What are those for? "No transactions": You mean no cross-collection and no cross-document transactions? Granted - but don't always need them either. "No hope for real applications": well... There are more issues and edge cases to slog through, I'm sure. But hopefully this gives you some ideas of how to solve common problems without distributed locking and relational databases. But then again, you can choose relational databases if they suit your problem.

  Read the article

• Failed to Install Xdebug

  - by burnt1ce

  've registered xdebug in php.ini (as per http://xdebug.org/docs/install) but it's not showing up when i run "php -m" or when i get a test page to run "phpinfo()". I've just installed the latest version of XAMPP. I've used both "zend_extention" and "zend_extention_ts" to specify the path of the xdebug dll. I ensured that my apache server restarted and used the latest change of my php.ini by executing "httpd -k restart". Can anyone provide any suggestions in getting xdebug to show up? Here are the contents of my php.ini file. [PHP] ;;;;;;;;;;;;;;;;;;; ; About php.ini ; ;;;;;;;;;;;;;;;;;;; ; PHP's initialization file, generally called php.ini, is responsible for ; configuring many of the aspects of PHP's behavior. ; PHP attempts to find and load this configuration from a number of locations. ; The following is a summary of its search order: ; 1. SAPI module specific location. ; 2. The PHPRC environment variable. (As of PHP 5.2.0) ; 3. A number of predefined registry keys on Windows (As of PHP 5.2.0) ; 4. Current working directory (except CLI) ; 5. The web server's directory (for SAPI modules), or directory of PHP ; (otherwise in Windows) ; 6. The directory from the --with-config-file-path compile time option, or the ; Windows directory (C:\windows or C:\winnt) ; See the PHP docs for more specific information. ; http://php.net/configuration.file ; The syntax of the file is extremely simple. Whitespace and Lines ; beginning with a semicolon are silently ignored (as you probably guessed). ; Section headers (e.g. [Foo]) are also silently ignored, even though ; they might mean something in the future. ; Directives following the section heading [PATH=/www/mysite] only ; apply to PHP files in the /www/mysite directory. Directives ; following the section heading [HOST=www.example.com] only apply to ; PHP files served from www.example.com. Directives set in these ; special sections cannot be overridden by user-defined INI files or ; at runtime. Currently, [PATH=] and [HOST=] sections only work under ; CGI/FastCGI. ; http://php.net/ini.sections ; Directives are specified using the following syntax: ; directive = value ; Directive names are *case sensitive* - foo=bar is different from FOO=bar. ; Directives are variables used to configure PHP or PHP extensions. ; There is no name validation. If PHP can't find an expected ; directive because it is not set or is mistyped, a default value will be used. ; The value can be a string, a number, a PHP constant (e.g. E_ALL or M_PI), one ; of the INI constants (On, Off, True, False, Yes, No and None) or an expression ; (e.g. E_ALL & ~E_NOTICE), a quoted string ("bar"), or a reference to a ; previously set variable or directive (e.g. ${foo}) ; Expressions in the INI file are limited to bitwise operators and parentheses: ; | bitwise OR ; ^ bitwise XOR ; & bitwise AND ; ~ bitwise NOT ; ! boolean NOT ; Boolean flags can be turned on using the values 1, On, True or Yes. ; They can be turned off using the values 0, Off, False or No. ; An empty string can be denoted by simply not writing anything after the equal ; sign, or by using the None keyword: ; foo = ; sets foo to an empty string ; foo = None ; sets foo to an empty string ; foo = "None" ; sets foo to the string 'None' ; If you use constants in your value, and these constants belong to a ; dynamically loaded extension (either a PHP extension or a Zend extension), ; you may only use these constants *after* the line that loads the extension. ;;;;;;;;;;;;;;;;;;; ; About this file ; ;;;;;;;;;;;;;;;;;;; ; PHP comes packaged with two INI files. One that is recommended to be used ; in production environments and one that is recommended to be used in ; development environments. ; php.ini-production contains settings which hold security, performance and ; best practices at its core. But please be aware, these settings may break ; compatibility with older or less security conscience applications. We ; recommending using the production ini in production and testing environments. ; php.ini-development is very similar to its production variant, except it's ; much more verbose when it comes to errors. We recommending using the ; development version only in development environments as errors shown to ; application users can inadvertently leak otherwise secure information. ;;;;;;;;;;;;;;;;;;; ; Quick Reference ; ;;;;;;;;;;;;;;;;;;; ; The following are all the settings which are different in either the production ; or development versions of the INIs with respect to PHP's default behavior. ; Please see the actual settings later in the document for more details as to why ; we recommend these changes in PHP's behavior. ; allow_call_time_pass_reference ; Default Value: On ; Development Value: Off ; Production Value: Off ; display_errors ; Default Value: On ; Development Value: On ; Production Value: Off ; display_startup_errors ; Default Value: Off ; Development Value: On ; Production Value: Off ; error_reporting ; Default Value: E_ALL & ~E_NOTICE ; Development Value: E_ALL | E_STRICT ; Production Value: E_ALL & ~E_DEPRECATED ; html_errors ; Default Value: On ; Development Value: On ; Production value: Off ; log_errors ; Default Value: Off ; Development Value: On ; Production Value: On ; magic_quotes_gpc ; Default Value: On ; Development Value: Off ; Production Value: Off ; max_input_time ; Default Value: -1 (Unlimited) ; Development Value: 60 (60 seconds) ; Production Value: 60 (60 seconds) ; output_buffering ; Default Value: Off ; Development Value: 4096 ; Production Value: 4096 ; register_argc_argv ; Default Value: On ; Development Value: Off ; Production Value: Off ; register_long_arrays ; Default Value: On ; Development Value: Off ; Production Value: Off ; request_order ; Default Value: None ; Development Value: "GP" ; Production Value: "GP" ; session.bug_compat_42 ; Default Value: On ; Development Value: On ; Production Value: Off ; session.bug_compat_warn ; Default Value: On ; Development Value: On ; Production Value: Off ; session.gc_divisor ; Default Value: 100 ; Development Value: 1000 ; Production Value: 1000 ; session.hash_bits_per_character ; Default Value: 4 ; Development Value: 5 ; Production Value: 5 ; short_open_tag ; Default Value: On ; Development Value: Off ; Production Value: Off ; track_errors ; Default Value: Off ; Development Value: On ; Production Value: Off ; url_rewriter.tags ; Default Value: "a=href,area=href,frame=src,form=,fieldset=" ; Development Value: "a=href,area=href,frame=src,input=src,form=fakeentry" ; Production Value: "a=href,area=href,frame=src,input=src,form=fakeentry" ; variables_order ; Default Value: "EGPCS" ; Development Value: "GPCS" ; Production Value: "GPCS" ;;;;;;;;;;;;;;;;;;;; ; php.ini Options ; ;;;;;;;;;;;;;;;;;;;; ; Name for user-defined php.ini (.htaccess) files. Default is ".user.ini" ;user_ini.filename = ".user.ini" ; To disable this feature set this option to empty value ;user_ini.filename = ; TTL for user-defined php.ini files (time-to-live) in seconds. Default is 300 seconds (5 minutes) ;user_ini.cache_ttl = 300 ;;;;;;;;;;;;;;;;;;;; ; Language Options ; ;;;;;;;;;;;;;;;;;;;; ; Enable the PHP scripting language engine under Apache. ; http://php.net/engine engine = On ; This directive determines whether or not PHP will recognize code between ; <? and ?> tags as PHP source which should be processed as such. It's been ; recommended for several years that you not use the short tag "short cut" and ; instead to use the full <?php and ?> tag combination. With the wide spread use ; of XML and use of these tags by other languages, the server can become easily ; confused and end up parsing the wrong code in the wrong context. But because ; this short cut has been a feature for such a long time, it's currently still ; supported for backwards compatibility, but we recommend you don't use them. ; Default Value: On ; Development Value: Off ; Production Value: Off ; http://php.net/short-open-tag short_open_tag = Off ; Allow ASP-style <% %> tags. ; http://php.net/asp-tags asp_tags = Off ; The number of significant digits displayed in floating point numbers. ; http://php.net/precision precision = 14 ; Enforce year 2000 compliance (will cause problems with non-compliant browsers) ; http://php.net/y2k-compliance y2k_compliance = On ; Output buffering is a mechanism for controlling how much output data ; (excluding headers and cookies) PHP should keep internally before pushing that ; data to the client. If your application's output exceeds this setting, PHP ; will send that data in chunks of roughly the size you specify. ; Turning on this setting and managing its maximum buffer size can yield some ; interesting side-effects depending on your application and web server. ; You may be able to send headers and cookies after you've already sent output ; through print or echo. You also may see performance benefits if your server is ; emitting less packets due to buffered output versus PHP streaming the output ; as it gets it. On production servers, 4096 bytes is a good setting for performance ; reasons. ; Note: Output buffering can also be controlled via Output Buffering Control ; functions. ; Possible Values: ; On = Enabled and buffer is unlimited. (Use with caution) ; Off = Disabled ; Integer = Enables the buffer and sets its maximum size in bytes. ; Note: This directive is hardcoded to Off for the CLI SAPI ; Default Value: Off ; Development Value: 4096 ; Production Value: 4096 ; http://php.net/output-buffering output_buffering = Off ; You can redirect all of the output of your scripts to a function. For ; example, if you set output_handler to "mb_output_handler", character ; encoding will be transparently converted to the specified encoding. ; Setting any output handler automatically turns on output buffering. ; Note: People who wrote portable scripts should not depend on this ini ; directive. Instead, explicitly set the output handler using ob_start(). ; Using this ini directive may cause problems unless you know what script ; is doing. ; Note: You cannot use both "mb_output_handler" with "ob_iconv_handler" ; and you cannot use both "ob_gzhandler" and "zlib.output_compression". ; Note: output_handler must be empty if this is set 'On' !!!! ; Instead you must use zlib.output_handler. ; http://php.net/output-handler ;output_handler = ; Transparent output compression using the zlib library ; Valid values for this option are 'off', 'on', or a specific buffer size ; to be used for compression (default is 4KB) ; Note: Resulting chunk size may vary due to nature of compression. PHP ; outputs chunks that are few hundreds bytes each as a result of ; compression. If you prefer a larger chunk size for better ; performance, enable output_buffering in addition. ; Note: You need to use zlib.output_handler instead of the standard ; output_handler, or otherwise the output will be corrupted. ; http://php.net/zlib.output-compression zlib.output_compression = Off ; http://php.net/zlib.output-compression-level ;zlib.output_compression_level = -1 ; You cannot specify additional output handlers if zlib.output_compression ; is activated here. This setting does the same as output_handler but in ; a different order. ; http://php.net/zlib.output-handler ;zlib.output_handler = ; Implicit flush tells PHP to tell the output layer to flush itself ; automatically after every output block. This is equivalent to calling the ; PHP function flush() after each and every call to print() or echo() and each ; and every HTML block. Turning this option on has serious performance ; implications and is generally recommended for debugging purposes only. ; http://php.net/implicit-flush ; Note: This directive is hardcoded to On for the CLI SAPI implicit_flush = Off ; The unserialize callback function will be called (with the undefined class' ; name as parameter), if the unserializer finds an undefined class ; which should be instantiated. A warning appears if the specified function is ; not defined, or if the function doesn't include/implement the missing class. ; So only set this entry, if you really want to implement such a ; callback-function. unserialize_callback_func = ; When floats & doubles are serialized store serialize_precision significant ; digits after the floating point. The default value ensures that when floats ; are decoded with unserialize, the data will remain the same. serialize_precision = 100 ; This directive allows you to enable and disable warnings which PHP will issue ; if you pass a value by reference at function call time. Passing values by ; reference at function call time is a deprecated feature which will be removed ; from PHP at some point in the near future. The acceptable method for passing a ; value by reference to a function is by declaring the reference in the functions ; definition, not at call time. This directive does not disable this feature, it ; only determines whether PHP will warn you about it or not. These warnings ; should enabled in development environments only. ; Default Value: On (Suppress warnings) ; Development Value: Off (Issue warnings) ; Production Value: Off (Issue warnings) ; http://php.net/allow-call-time-pass-reference allow_call_time_pass_reference = On ; Safe Mode ; http://php.net/safe-mode safe_mode = Off ; By default, Safe Mode does a UID compare check when ; opening files. If you want to relax this to a GID compare, ; then turn on safe_mode_gid. ; http://php.net/safe-mode-gid safe_mode_gid = Off ; When safe_mode is on, UID/GID checks are bypassed when ; including files from this directory and its subdirectories. ; (directory must also be in include_path or full path must ; be used when including) ; http://php.net/safe-mode-include-dir safe_mode_include_dir = ; When safe_mode is on, only executables located in the safe_mode_exec_dir ; will be allowed to be executed via the exec family of functions. ; http://php.net/safe-mode-exec-dir safe_mode_exec_dir = ; Setting certain environment variables may be a potential security breach. ; This directive contains a comma-delimited list of prefixes. In Safe Mode, ; the user may only alter environment variables whose names begin with the ; prefixes supplied here. By default, users will only be able to set ; environment variables that begin with PHP_ (e.g. PHP_FOO=BAR). ; Note: If this directive is empty, PHP will let the user modify ANY ; environment variable! ; http://php.net/safe-mode-allowed-env-vars safe_mode_allowed_env_vars = PHP_ ; This directive contains a comma-delimited list of environment variables that ; the end user won't be able to change using putenv(). These variables will be ; protected even if safe_mode_allowed_env_vars is set to allow to change them. ; http://php.net/safe-mode-protected-env-vars safe_mode_protected_env_vars = LD_LIBRARY_PATH ; open_basedir, if set, limits all file operations to the defined directory ; and below. This directive makes most sense if used in a per-directory ; or per-virtualhost web server configuration file. This directive is ; *NOT* affected by whether Safe Mode is turned On or Off. ; http://php.net/open-basedir ;open_basedir = ; This directive allows you to disable certain functions for security reasons. ; It receives a comma-delimited list of function names. This directive is ; *NOT* affected by whether Safe Mode is turned On or Off. ; http://php.net/disable-functions disable_functions = ; This directive allows you to disable certain classes for security reasons. ; It receives a comma-delimited list of class names. This directive is ; *NOT* affected by whether Safe Mode is turned On or Off. ; http://php.net/disable-classes disable_classes = ; Colors for Syntax Highlighting mode. Anything that's acceptable in ; <span style="color: ???????"> would work. ; http://php.net/syntax-highlighting ;highlight.string = #DD0000 ;highlight.comment = #FF9900 ;highlight.keyword = #007700 ;highlight.bg = #FFFFFF ;highlight.default = #0000BB ;highlight.html = #000000 ; If enabled, the request will be allowed to complete even if the user aborts ; the request. Consider enabling it if executing long requests, which may end up ; being interrupted by the user or a browser timing out. PHP's default behavior ; is to disable this feature. ; http://php.net/ignore-user-abort ;ignore_user_abort = On ; Determines the size of the realpath cache to be used by PHP. This value should ; be increased on systems where PHP opens many files to reflect the quantity of ; the file operations performed. ; http://php.net/realpath-cache-size ;realpath_cache_size = 16k ; Duration of time, in seconds for which to cache realpath information for a given ; file or directory. For systems with rarely changing files, consider increasing this ; value. ; http://php.net/realpath-cache-ttl ;realpath_cache_ttl = 120 ;;;;;;;;;;;;;;;;; ; Miscellaneous ; ;;;;;;;;;;;;;;;;; ; Decides whether PHP may expose the fact that it is installed on the server ; (e.g. by adding its signature to the Web server header). It is no security ; threat in any way, but it makes it possible to determine whether you use PHP ; on your server or not. ; http://php.net/expose-php expose_php = On ;;;;;;;;;;;;;;;;;;; ; Resource Limits ; ;;;;;;;;;;;;;;;;;;; ; Maximum execution time of each script, in seconds ; http://php.net/max-execution-time ; Note: This directive is hardcoded to 0 for the CLI SAPI max_execution_time = 60 ; Maximum amount of time each script may spend parsing request data. It's a good ; idea to limit this time on productions servers in order to eliminate unexpectedly ; long running scripts. ; Note: This directive is hardcoded to -1 for the CLI SAPI ; Default Value: -1 (Unlimited) ; Development Value: 60 (60 seconds) ; Production Value: 60 (60 seconds) ; http://php.net/max-input-time max_input_time = 60 ; Maximum input variable nesting level ; http://php.net/max-input-nesting-level ;max_input_nesting_level = 64 ; Maximum amount of memory a script may consume (128MB) ; http://php.net/memory-limit memory_limit = 128M ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; Error handling and logging ; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; This directive informs PHP of which errors, warnings and notices you would like ; it to take action for. The recommended way of setting values for this ; directive is through the use of the error level constants and bitwise ; operators. The error level constants are below here for convenience as well as ; some common settings and their meanings. ; By default, PHP is set to take action on all errors, notices and warnings EXCEPT ; those related to E_NOTICE and E_STRICT, which together cover best practices and ; recommended coding standards in PHP. For performance reasons, this is the ; recommend error reporting setting. Your production server shouldn't be wasting ; resources complaining about best practices and coding standards. That's what ; development servers and development settings are for. ; Note: The php.ini-development file has this setting as E_ALL | E_STRICT. This ; means it pretty much reports everything which is exactly what you want during ; development and early testing. ; ; Error Level Constants: ; E_ALL - All errors and warnings (includes E_STRICT as of PHP 6.0.0) ; E_ERROR - fatal run-time errors ; E_RECOVERABLE_ERROR - almost fatal run-time errors ; E_WARNING - run-time warnings (non-fatal errors) ; E_PARSE - compile-time parse errors ; E_NOTICE - run-time notices (these are warnings which often result ; from a bug in your code, but it's possible that it was ; intentional (e.g., using an uninitialized variable and ; relying on the fact it's automatically initialized to an ; empty string) ; E_STRICT - run-time notices, enable to have PHP suggest changes ; to your code which will ensure the best interoperability ; and forward compatibility of your code ; E_CORE_ERROR - fatal errors that occur during PHP's initial startup ; E_CORE_WARNING - warnings (non-fatal errors) that occur during PHP's ; initial startup ; E_COMPILE_ERROR - fatal compile-time errors ; E_COMPILE_WARNING - compile-time warnings (non-fatal errors) ; E_USER_ERROR - user-generated error message ; E_USER_WARNING - user-generated warning message ; E_USER_NOTICE - user-generated notice message ; E_DEPRECATED - warn about code that will not work in future versions ; of PHP ; E_USER_DEPRECATED - user-generated deprecation warnings ; ; Common Values: ; E_ALL & ~E_NOTICE (Show all errors, except for notices and coding standards warnings.) ; E_ALL & ~E_NOTICE | E_STRICT (Show all errors, except for notices) ; E_COMPILE_ERROR|E_RECOVERABLE_ERROR|E_ERROR|E_CORE_ERROR (Show only errors) ; E_ALL | E_STRICT (Show all errors, warnings and notices including coding standards.) ; Default Value: E_ALL & ~E_NOTICE ; Development Value: E_ALL | E_STRICT ; Production Value: E_ALL & ~E_DEPRECATED ; http://php.net/error-reporting error_reporting = E_ALL & ~E_NOTICE & ~E_DEPRECATED ; This directive controls whether or not and where PHP will output errors, ; notices and warnings too. Error output is very useful during development, but ; it could be very dangerous in production environments. Depending on the code ; which is triggering the error, sensitive information could potentially leak ; out of your application such as database usernames and passwords or worse. ; It's recommended that errors be logged on production servers rather than ; having the errors sent to STDOUT. ; Possible Values: ; Off = Do not display any errors ; stderr = Display errors to STDERR (affects only CGI/CLI binaries!) ; On or stdout = Display errors to STDOUT ; Default Value: On ; Development Value: On ; Production Value: Off ; http://php.net/display-errors display_errors = On ; The display of errors which occur during PHP's startup sequence are handled ; separately from display_errors. PHP's default behavior is to suppress those ; errors from clients. Turning the display of startup errors on can be useful in ; debugging configuration problems. But, it's strongly recommended that you ; leave this setting off on production servers. ; Default Value: Off ; Development Value: On ; Production Value: Off ; http://php.net/display-startup-errors display_startup_errors = On ; Besides displaying errors, PHP can also log errors to locations such as a ; server-specific log, STDERR, or a location specified by the error_log ; directive found below. While errors should not be displayed on productions ; servers they should still be monitored and logging is a great way to do that. ; Default Value: Off ; Development Value: On ; Production Value: On ; http://php.net/log-errors log_errors = Off ; Set maximum length of log_errors. In error_log information about the source is ; added. The default is 1024 and 0 allows to not apply any maximum length at all. ; http://php.net/log-errors-max-len log_errors_max_len = 1024 ; Do not log repeated messages. Repeated errors must occur in same file on same ; line unless ignore_repeated_source is set true. ; http://php.net/ignore-repeated-errors ignore_repeated_errors = Off ; Ignore source of message when ignoring repeated messages. When this setting ; is On you will not log errors with repeated messages from different files or ; source lines. ; http://php.net/ignore-repeated-source ignore_repeated_source = Off ; If this parameter is set to Off, then memory leaks will not be shown (on ; stdout or in the log). This has only effect in a debug compile, and if ; error reporting includes E_WARNING in the allowed list ; http://php.net/report-memleaks report_memleaks = On ; This setting is on by default. ;report_zend_debug = 0 ; Store the last error/warning message in $php_errormsg (boolean). Setting this value ; to On can assist in debugging and is appropriate for development servers. It should ; however be disabled on production servers. ; Default Value: Off ; Development Value: On ; Production Value: Off ; http://php.net/track-errors track_errors = Off ; Turn off normal error reporting and emit XML-RPC error XML ; http://php.net/xmlrpc-errors ;xmlrpc_errors = 0 ; An XML-RPC faultCode ;xmlrpc_error_number = 0 ; When PHP displays or logs an error, it has the capability of inserting html ; links to documentation related to that error. This directive controls whether ; those HTML links appear in error messages or not. For performance and security ; reasons, it's recommended you disable this on production servers. ; Note: This directive is hardcoded to Off for the CLI SAPI ; Default Value: On ; Development Value: On ; Production value: Off ; http://php.net/html-errors html_errors = On ; If html_errors is set On PHP produces clickable error messages that direct ; to a page describing the error or function causing the error in detail. ; You can download a copy of the PHP manual from http://php.net/docs ; and change docref_root to the base URL of your local copy including the ; leading '/'. You must also specify the file extension being used including ; the dot. PHP's default behavior is to leave these settings empty. ; Note: Never use this feature for production boxes. ; http://php.net/docref-root ; Examples ;docref_root = "/phpmanual/" ; http://php.net/docref-ext ;docref_ext = .html ; String to output before an error message. PHP's default behavior is to leave ; this setting blank. ; http://php.net/error-prepend-string ; Example: ;error_prepend_string = "<font color=#ff0000>" ; String to output after an error message. PHP's default behavior is to leave ; this setting blank. ; http://php.net/error-append-string ; Example: ;error_append_string = "</font>" ; Log errors to specified file. PHP's default behavior is to leave this value ; empty. ; http://php.net/error-log ; Example: ;error_log = php_errors.log ; Log errors to syslog (Event Log on NT, not valid in Windows 95). ;error_log = syslog ;error_log = "C:\xampp\apache\logs\php_error.log" ;;;;;;;;;;;;;;;;; ; Data Handling ; ;;;;;;;;;;;;;;;;; ; Note - track_vars is ALWAYS enabled ; The separator used in PHP generated URLs to separate arguments. ; PHP's default setting is "&". ; http://php.net/arg-separator.output ; Example: arg_separator.output = "&amp;" ; List of separator(s) used by PHP to parse input URLs into variables. ; PHP's default setting is "&

  Read the article

• Understanding the memory consumption on iPhone

  - by zoul

  Hello! I am working on a 2D iPhone game using OpenGL ES and I keep hitting the 24 MB memory limit – my application keeps crashing with the error code 101. I tried real hard to find where the memory goes, but the numbers in Instruments are still much bigger than what I would expect. I ran the application with the Memory Monitor, Object Alloc, Leaks and OpenGL ES instruments. When the application gets loaded, free physical memory drops from 37 MB to 23 MB, the Object Alloc settles around 7 MB, Leaks show two or three leaks a few bytes in size, the Gart Object Size is about 5 MB and Memory Monitor says the application takes up about 14 MB of real memory. I am perplexed as where did the memory go – when I dig into the Object Allocations, most of the memory is in the textures, exactly as I would expect. But both my own texture allocation counter and the Gart Object Size agree that the textures should take up somewhere around 5 MB. I am not aware of allocating anything else that would be worth mentioning, and the Object Alloc agrees. Where does the memory go? (I would be glad to supply more details if this is not enough.) Update: I really tried to find where I could allocate so much memory, but with no results. What drives me wild is the difference between the Object Allocations (~7 MB) and real memory usage as shown by Memory Monitor (~14 MB). Even if there were huge leaks or huge chunks of memory I forget about, the should still show up in the Object Allocations, shouldn’t they? I’ve already tried the usual suspects, ie. the UIImage with its caching, but that did not help. Is there a way to track memory usage “debugger-style”, line by line, watching each statement’s impact on memory usage? What I have found so far: I really am using that much memory. It is not easy to measure the real memory consumption, but after a lot of counting I think the memory consumption is really that high. My fault. I found no easy way to measure the memory used. The Memory Monitor numbers are accurate (these are the numbers that really matter), but the Memory Monitor can’t tell you where exactly the memory goes. The Object Alloc tool is almost useless for tracking the real memory usage. When I create a texture, the allocated memory counter goes up for a while (reading the texture into the memory), then drops (passing the texture data to OpenGL, freeing). This is OK, but does not always happen – sometimes the memory usage stays high even after the texture has been passed on to OpenGL and freed from “my” memory. This means that the total amount of memory allocated as shown by the Object Alloc tool is smaller than the real total memory consumption, but bigger than the real consumption minus textures (real – textures < object alloc < real). Go figure. I misread the Programming Guide. The memory limit of 24 MB applies to textures and surfaces, not the whole application. The actual red line lies a bit further, but I could not find any hard numbers. The consensus is that 25–30 MB is the ceiling. When the system gets short on memory, it starts sending the memory warning. I have almost nothing to free, but other applications do release some memory back to the system, especially Safari (which seems to be caching the websites). When the free memory as shown in the Memory Monitor goes zero, the system starts killing. I had to bite the bullet and rewrite some parts of the code to be more efficient on memory, but I am probably still pushing it. I

  Read the article

• Java Fx Data bind not working with File Read

  - by rjha94

  Hi I am using a very simple JavaFx client to upload files. I read the file in chunks of 1 MB (using Byte Buffer) and upload using multi part POST to a PHP script. I want to update the progress bar of my client to show progress after each chunk is uploaded. The calculations for upload progress look correct but the progress bar is not updated. I am using bind keyword. I am no JavaFx expert and I am hoping some one can point out my mistake. I am writing this client to fix the issues posted here (http://stackoverflow.com/questions/2447837/upload-1gb-files-using-chunking-in-php) /* * Main.fx * * Created on Mar 16, 2010, 1:58:32 PM */ package webgloo; import javafx.stage.Stage; import javafx.scene.Scene; import javafx.scene.layout.VBox; import javafx.geometry.VPos; import javafx.scene.control.Button; import javafx.scene.control.Label; import javafx.scene.layout.HBox; import javafx.scene.layout.LayoutInfo; import javafx.scene.text.Font; import javafx.scene.control.ProgressBar; import java.io.FileInputStream; /** * @author rajeev jha */ var totalBytes:Float = 1; var bytesWritten:Float = 0; var progressUpload:Float; var uploadURI = "http://www.test1.com/test/receiver.php"; var postMax = 1024000 ; function uploadFile(inputFile: java.io.File) { totalBytes = inputFile.length(); bytesWritten = 1; println("To-Upload - {totalBytes}"); var is = new FileInputStream(inputFile); var fc = is.getChannel(); //1 MB byte buffer var chunkCount = 0; var bb = java.nio.ByteBuffer.allocate(postMax); while(fc.read(bb) >= 0){ println("loop:start"); bb.flip(); var limit = bb.limit(); var bytes = GigaFileUploader.getBufferBytes(bb.array(), limit); var content = GigaFileUploader.createPostContent(inputFile.getName(), bytes); GigaFileUploader.upload(uploadURI, content); bytesWritten = bytesWritten + limit ; progressUpload = 1.0 * bytesWritten / totalBytes ; println("Progress is - {progressUpload}"); chunkCount++; bb.clear(); println("loop:end"); } } var label = Label { font: Font { size: 12 } text: bind "Uploaded - {bytesWritten * 100 / (totalBytes)}%" layoutInfo: LayoutInfo { vpos: VPos.CENTER maxWidth: 120 minWidth: 120 width: 120 height: 30 } } def jFileChooser = new javax.swing.JFileChooser(); jFileChooser.setApproveButtonText("Upload"); var button = Button { text: "Upload" layoutInfo: LayoutInfo { width: 100 height: 30 } action: function () { var outputFile = jFileChooser.showOpenDialog(null); if (outputFile == javax.swing.JFileChooser.APPROVE_OPTION) { uploadFile(jFileChooser.getSelectedFile()); } } } var hBox = HBox { spacing: 10 content: [label, button] } var progressBar = ProgressBar { progress: bind progressUpload layoutInfo: LayoutInfo { width: 240 height: 30 } } var vBox = VBox { spacing: 10 content: [hBox, progressBar] layoutX: 10 layoutY: 10 } Stage { title: "Upload File" width: 270 height: 120 scene: Scene { content: [vBox] } resizable: false }

  Read the article

• How to create Large resumable download from a secured location .NET

  - by Kelvin H

  I need to preface I'm not a .NET coder at all, but to get partial functionality, I modified a technet chunkedfilefetch.aspx script that uses chunked Data Reading and writing Streamed method of doing file transfer, to get me half-way. iStream = New System.IO.FileStream(path, System.IO.FileMode.Open, _ IO.FileAccess.Read, IO.FileShare.Read) dataToRead = iStream.Length Response.ContentType = "application/octet-stream" Response.AddHeader("Content-Length", file.Length.ToString()) Response.AddHeader("Content-Disposition", "attachment; filename=" & filedownload) ' Read and send the file 16,000 bytes at a time. ' While dataToRead 0 If Response.IsClientConnected Then length = iStream.Read(buffer, 0, 16000) Response.OutputStream.Write(buffer, 0, length) Response.Flush() ReDim buffer(16000) ' Clear the buffer ' dataToRead = dataToRead - length Else ' Prevent infinite loop if user disconnects ' dataToRead = -1 End If End While This works great on files up to 2GB and is fully functioning now.. But only one problem it doesn't allow for resume. I took the original code called it fetch.aspx and pass an orderNUM through the URL. fetch.aspx&ordernum=xxxxxxx It then reads the filename/location from the database occording to the ordernumber, and chunks it out from a secured location NOT under the webroot. I need a way to make this resumable, by the nature of the internet and large files people always get disconnected and would like to resume where they left off. But any resumable articles i've read, assume the file is within the webroot.. ie. http://www.devx.com/dotnet/Article/22533/1954 Great article and works well, but I need to stream from a secured location. I'm not a .NET coder at all, at best i can do a bit of coldfusion, if anyone could help me modify a handler to do this, i would really appreciate it. Requirements: I Have a working fetch.aspx script that functions well and uses the above code snippet as a base for the streamed downloading. Download files are large 600MB and are stored in a secured location outside of the webroot. Users click on the fetch.aspx to start the download, and would therefore be clicking it again if it was to fail. If the ext is a .ASPX and the file being sent is a AVI, clicking on it would completely bypass an IHTTP handler mapped to .AVI ext, so this confuses me From what I understand the browser will read and match etag value and file modified date to determine they are talking about the same file, then a subsequent accept-range is exchanged between the browser and IIS. Since this dialog happens with IIS, we need to use a handler to intercept and respond accordingly, but clicking on the link would send it to an ASPX file which the handeler needs to be on an AVI fiel.. Also confusing me. If there is a way to request the initial HTTP request header containing etag, accept-range into the normal .ASPX file, i could read those values and if the accept-range and etag exist, start chunking at that byte value somehow? but I couldn't find a way to transfer the http request headers since they seem to get lost at the IIS level. OrderNum which is passed in the URL string is unique and could be used as the ETag Response.AddHeader("ETag", request("ordernum")) Files need to be resumable and chunked out due to size. File extensions are .AVI so a handler could be written around it. IIS 6.0 Web Server Any help would really be appreciated, i've been reading and reading and downloading code, but none of the examples given meet my situation with the original file being streamed from outside of the webroot. Please help me get a handle on these httphandlers :)

  Read the article

• WCF REST Question, Binding, Configuration

  - by Ethan McGee

  I am working on a WCF rest interface using json. I have wrapped the service in a windows service to host the service but I am now having trouble getting the service to be callable. I am not sure exactly what is wrong. The basic idea is that I want to host the service on a remote server so I want the service mapped to port localhost:7600 so that it can be invoked by posting data to [server_ip]:7600. The problem is most likely in the configuration file, since I am new to WCF and Rest I wasn't really sure what to type for the configuration so sorry if it's a total mess. I removed several chunks of code and comments to make it a little easier to read. These functions should have no bearing on the service since they call only C# functions. WCF Service Code using System; using System.Collections.Generic; using System.Linq; using System.ServiceModel; using System.ServiceModel.Activation; using System.ServiceModel.Web; using System.Text; namespace PCMiler_Connect { public class ZIP_List_Container { public string[] ZIP_List { get; set; } public string Optimized { get; set; } public string Calc_Type { get; set; } public string Cross_International_Borders { get; set; } public string Use_Kilometers { get; set; } public string Hazard_Level { get; set; } public string OK_To_Change_Destination { get; set; } } [ServiceContract] [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] [ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)] public class PCMiler_Webservice { [WebInvoke(Method = "POST", UriTemplate = "", ResponseFormat = WebMessageFormat.Json, RequestFormat = WebMessageFormat.Json), OperationContract] public List<string> Calculate_Distance(ZIP_List_Container container) { return new List<string>(){ distance.ToString(), time.ToString() }; } } } XML Config File <?xml version="1.0" encoding="utf-8"?> <configuration> <system.serviceModel> <services> <service name="PCMiler_Connect.PCMiler_Webservice"> <endpoint address="" behaviorConfiguration="jsonBehavior" binding="webHttpBinding" bindingConfiguration="" contract="PCMiler_Connect.PCMiler_Webservice" /> <host> <baseAddresses> <add baseAddress="http://localhost:7600/" /> </baseAddresses> </host> </service> </services> <behaviors> <endpointBehaviors> <behavior name="jsonBehavior"> <enableWebScript/> </behavior> </endpointBehaviors> </behaviors> </system.serviceModel> </configuration> Service Wrapper using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Diagnostics; using System.Linq; using System.ServiceProcess; using System.ServiceModel; using System.Text; using System.Threading; namespace PCMiler_WIN_Service { public partial class Service1 : ServiceBase { ServiceHost host; public Service1() { InitializeComponent(); } protected override void OnStart(string[] args) { host = new ServiceHost(typeof(PCMiler_Connect.PCMiler_Webservice)); Thread thread = new Thread(new ThreadStart(host.Open)); } protected override void OnStop() { if (host != null) { host.Close(); host = null; } } } }

  Read the article

• Evidence-Based-Scheduling - are estimations only as accurate as the work-plan they're based on?

  - by Assaf Lavie

  I've been using FogBugz's Evidence Based Scheduling (for the uninitiated, Joel explains) for a while now and there's an inherent problem I can't seem to work around. The system is good at telling me the probability that a given project will be delivered at some date, given the detailed list of tasks that comprise the project. However, it does not take into account the fact that during development additional tasks always pop up. Now, there's the garbage-can approach of creating a generic task/scheduled-item for "last minute hacks" or "integration tasks", or what have you, but that clearly goes against the idea of aggregating the estimates of many small cases. It's often the case that during the development stage of a project you realize that there's a whole area your planning didn't cover, because, well, that's the nature of developing stuff that hasn't been developed before. So now your ~3 month project may very well turn into a 6 month project, but not because your estimations were off (you could be the best estimator in the world, for those task the comprised your initial work plan); rather because you ended up adding a whole bunch of new tasks that weren't there to begin with. EBS doesn't help you with that. It could, theoretically (I guess). It could, perhaps, measure the amount of work you add to a project over time and take that into consideration when estimating the time remaining on a given project. Just a thought. In other words, EBS works on a task basis, but not on a project/release basis - but the latter is what's important. It's what your boss typically cares about - delivery date, not the time it takes to finish each task along the way, and not the time it would have taken, if your planning was perfect. So the question is (yes, there's a question here, don't close it): What's your methodology when it comes to using EBS in FogBugz and how do you solve the problem above, which seems to be a main cause of schedule delays and mispredictions? Edit Some more thoughts after reading a few answers: If it comes down to having to choose which delivery date you're comfortable presenting to your higher-ups by squinting at the delivery-probability graph and choosing 80%, or 95%, or 60% (based on what, exactly?) then we've resorted to plain old buffering/factoring of our estimates. In which case, couldn't we have skipped the meticulous case by case hour-sized estimation effort step? By forcing ourselves to break down tasks that take more than a day into smaller chunks of work haven't we just deluded ourselves into thinking our planning is as tight and thorough as it could be? People may be consistently bad estimators that do not even learn from their past mistakes. In that respect, having an EBS system is certainly better than not having one. But what can we do about the fact that we're not that good in planning as well? I'm not sure it's a problem that can be solved by a similar system. Our estimates are wrong because of tendencies to be overly optimistic/pessimistic about certain tasks, and because of neglect to account for systematic delays (e.g. sick days, major bug crisis) - and usually not because we lack knowledge about the work that needs to be done. Our planning, on the other hand, is often incomplete because we simply don't have enough knowledge in this early stage; and I don't see how an EBS-like system could fill that gap. So we're back to methodology. We need to find a way to accommodate bad or incomplete work plans that's better than voodoo-multiplication.

  Read the article

• to understand the code- how the heap is written in process migration in solaris

  - by akshay

  hi guys i need help understanding what this piece of code actually does as it is a part of my project i am stuck here. the code is from libckpt on solaris. /********************************** * function: write_heap * args: map_fd -- file descriptor for map file * data_fd -- file descriptor for data file * returns: no. of chunks written on success, -1 on failure * side effects: writes all included segments of the heap to ckpt files * misc.: If we are forking and copyonwrite is set, we will write the heap from bottom to top, moving the brk pointer up each time so that we don't get a page copied if the * called from: take_ckpt() ***********************************/ static int write_heap(int map_fd, int data_fd) { Dlist curptr, endptr; int no_chunks=0, pn; long size; caddr_t stop, addr; if(ckptflags.incremental){ /-- incremental checkpointing on? --/ endptr = ckptglobals.inc_list-main-flink; /*-- for each included chunk of the heap --*/ for(curptr = ckptglobals.inc_list->main->blink->blink; curptr != endptr; curptr = curptr->blink){ /*-- write out the last page in the included chunk --*/ stop = curptr->addr; pn = ((long)curptr->stop - (long)sys.DATASTART) / PAGESIZE; if(isdirty(pn)){ addr = (caddr_t)max((long)curptr->addr, (long)((pn * PAGESIZE) + sys.DATASTART)); size = (long)curptr->stop - (long)addr; debug(stderr, "DEBUG: Writing heap from 0x%x to 0x%x, pn = %d\n", addr, addr+size, pn); if(write_chunk(addr, size, map_fd, data_fd) == -1){ return -1; } if((int)addr > (int)(&end) && ckptflags.enhanced_fork){ brk(addr); } no_chunks++; } /*-- write out all the whole pages in the middle of the chunk --*/ for(pn--; pn * PAGESIZE + sys.DATASTART >= stop; pn--){ if(isdirty(pn)){ addr = (caddr_t)((pn * PAGESIZE) + sys.DATASTART); debug(stderr, "DEBUG: Writing heap from 0x%x to 0x%x, pn = %d\n", addr, addr+PAGESIZE, pn); if(write_chunk(addr, PAGESIZE, map_fd, data_fd) == -1){ return -1; } if((int)addr > (int)(&end) && ckptflags.enhanced_fork){ brk(addr); } no_chunks++; } } /*-- write out the first page in the included chunk --*/ addr = curptr->addr; size = ((pn+1) * PAGESIZE + sys.DATASTART) - addr; if(size > 0 && (isdirty(pn))){ debug(stderr, "DEBUG: Writing heap from 0x%x to 0x%x\n", addr, addr+size); if(write_chunk(addr, size, map_fd, data_fd) == -1){ return -1; } if((int)addr > (int)(&end) && ckptflags.enhanced_fork){ brk(addr); } no_chunks++; } } } else{ /-- incremental checkpointing off! --/ endptr = ckptglobals.inc_list-main-blink; /*-- for each included chunk of the heap --*/ for(curptr = ckptglobals.inc_list->main->flink->flink; curptr != endptr; curptr = curptr->flink){ debug(stderr, "DEBUG: saving memory from 0x%x to 0x%x\n", curptr->addr, curptr->addr+curptr->size); if(write_chunk(curptr->addr, curptr->size, map_fd, data_fd) == -1){ return -1; } if((int)addr > (int)(&end) && ckptflags.enhanced_fork){ brk(addr); } no_chunks++; } } return no_chunks; }

  Read the article

• Random Complete System Unresponsiveness Running Mathematical Functions

  - by Computer Guru

  I have a program that loads a file (anywhere from 10MB to 5GB) a chunk at a time (ReadFile), and for each chunk performs a set of mathematical operations (basically calculates the hash). After calculating the hash, it stores info about the chunk in an STL map (basically <chunkID, hash>) and then writes the chunk itself to another file (WriteFile). That's all it does. This program will cause certain PCs to choke and die. The mouse begins to stutter, the task manager takes 2 min to show, ctrl+alt+del is unresponsive, running programs are slow.... the works. I've done literally everything I can think of to optimize the program, and have triple-checked all objects. What I've done: Tried different (less intensive) hashing algorithms. Switched all allocations to nedmalloc instead of the default new operator Switched from stl::map to unordered_set, found the performance to still be abysmal, so I switched again to Google's dense_hash_map. Converted all objects to store pointers to objects instead of the objects themselves. Caching all Read and Write operations. Instead of reading a 16k chunk of the file and performing the math on it, I read 4MB into a buffer and read 16k chunks from there instead. Same for all write operations - they are coalesced into 4MB blocks before being written to disk. Run extensive profiling with Visual Studio 2010, AMD Code Analyst, and perfmon. Set the thread priority to THREAD_MODE_BACKGROUND_BEGIN Set the thread priority to THREAD_PRIORITY_IDLE Added a Sleep(100) call after every loop. Even after all this, the application still results in a system-wide hang on certain machines under certain circumstances. Perfmon and Process Explorer show minimal CPU usage (with the sleep), no constant reads/writes from disk, few hard pagefaults (and only ~30k pagefaults in the lifetime of the application on a 5GB input file), little virtual memory (never more than 150MB), no leaked handles, no memory leaks. The machines I've tested it on run Windows XP - Windows 7, x86 and x64 versions included. None have less than 2GB RAM, though the problem is always exacerbated under lower memory conditions. I'm at a loss as to what to do next. I don't know what's causing it - I'm torn between CPU or Memory as the culprit. CPU because without the sleep and under different thread priorities the system performances changes noticeably. Memory because there's a huge difference in how often the issue occurs when using unordered_set vs Google's dense_hash_map. What's really weird? Obviously, the NT kernel design is supposed to prevent this sort of behavior from ever occurring (a user-mode application driving the system to this sort of extreme poor performance!?)..... but when I compile the code and run it on OS X or Linux (it's fairly standard C++ throughout) it performs excellently even on poor machines with little RAM and weaker CPUs. What am I supposed to do next? How do I know what the hell it is that Windows is doing behind the scenes that's killing system performance, when all the indicators are that the application itself isn't doing anything extreme? Any advice would be most welcome.

  Read the article

• How do I maximize code coverage?

  - by naivedeveloper

  Hey all, the following is a snippet of code taken from the unix ptx utility. I'm attempting to maximize code coverage on this utility, but I am unable to reach the indicated portion of code. Admittedly, I'm not as strong in my C skills as I used to be. The portion of code is indicated with comments, but it is towards the bottom of the block. if (used_length == allocated_length) { allocated_length += (1 << SWALLOW_REALLOC_LOG); block->start = (char *) xrealloc (block->start, allocated_length); } Any help interpreting the indicated portion in order to cover that block would be greatly appreciated. /* Reallocation step when swallowing non regular files. The value is not the actual reallocation step, but its base two logarithm. */ #define SWALLOW_REALLOC_LOG 12 static void swallow_file_in_memory (const char *file_name, BLOCK *block) { int file_handle; /* file descriptor number */ struct stat stat_block; /* stat block for file */ size_t allocated_length; /* allocated length of memory buffer */ size_t used_length; /* used length in memory buffer */ int read_length; /* number of character gotten on last read */ /* As special cases, a file name which is NULL or "-" indicates standard input, which is already opened. In all other cases, open the file from its name. */ bool using_stdin = !file_name || !*file_name || strcmp (file_name, "-") == 0; if (using_stdin) file_handle = STDIN_FILENO; else if ((file_handle = open (file_name, O_RDONLY)) < 0) error (EXIT_FAILURE, errno, "%s", file_name); /* If the file is a plain, regular file, allocate the memory buffer all at once and swallow the file in one blow. In other cases, read the file repeatedly in smaller chunks until we have it all, reallocating memory once in a while, as we go. */ if (fstat (file_handle, &stat_block) < 0) error (EXIT_FAILURE, errno, "%s", file_name); if (S_ISREG (stat_block.st_mode)) { size_t in_memory_size; block->start = (char *) xmalloc ((size_t) stat_block.st_size); if ((in_memory_size = read (file_handle, block->start, (size_t) stat_block.st_size)) != stat_block.st_size) { error (EXIT_FAILURE, errno, "%s", file_name); } block->end = block->start + in_memory_size; } else { block->start = (char *) xmalloc ((size_t) 1 << SWALLOW_REALLOC_LOG); used_length = 0; allocated_length = (1 << SWALLOW_REALLOC_LOG); while (read_length = read (file_handle, block->start + used_length, allocated_length - used_length), read_length > 0) { used_length += read_length; /* Cannot cover from this point...*/ if (used_length == allocated_length) { allocated_length += (1 << SWALLOW_REALLOC_LOG); block->start = (char *) xrealloc (block->start, allocated_length); } /* ...to this point. */ } if (read_length < 0) error (EXIT_FAILURE, errno, "%s", file_name); block->end = block->start + used_length; } /* Close the file, but only if it was not the standard input. */ if (! using_stdin && close (file_handle) != 0) error (EXIT_FAILURE, errno, "%s", file_name); }

  Read the article

• Why don't I just build the whole web app in Javascript and Javascript HTML Templates?

  - by viatropos

  I'm getting to the point on an app where I need to start caching things, and it got me thinking... In some parts of the app, I render table rows (jqGrid, slickgrid, etc.) or fancy div rows (like in the New Twitter) by grabbing pure JSON and running it through something like Mustache, jquery.tmpl, etc. In other parts of the app, I just render the info in pure HTML (server-side HAML templates), and if there's searching/paginating, I just go to a new URL and load a new HTML page. Now the problem is in caching and maintainability. On one hand I'm thinking, if everything was built using Javascript HTML Templates, then my app would serve just an HTML layout/shell, and a bunch of JSON. If you look at the Facebook and Twitter HTML source, that's basically what they're doing (95% json/javascript, 5% html). This would make it so my app only needed to cache JSON (pages, actions, and/or records). Which means you'd hit the cache no matter if you were some remote api developer accessing a JSON api, or the strait web app. That is, I don't need 2 caches, one for the JSON, one for the HTML. That seems like it'd cut my cache store down in half, and streamline things a little bit. On the other hand, I'm thinking, from what I've seen/experienced, generating static HTML server-side, and caching that, seems to be much better performance wise cross-browser; you get the graphics instantly and don't have to wait that split-second for javascript to render it. StackOverflow seems to do everything in plain HTML, and you can tell... everything appears at once. Notice how though on twitter.com, the page is blank for .5-1 seconds, and the page chunks in: the javascript has to render the json. The downside with this is that, for anything dynamic (like endless scrolling, or grids), I'd have to create javascript templates anyway... so now I have server-side HAML templates, client-side javascript templates, and a lot more to cache. My question is, is there any consensus on how to approach this? What are the benefits and drawbacks from your experience of mixing the two versus going 100% with one over the other? Update: Some reasons that factor into why I haven't yet made the decision to go with 100% javascript templating are: Performance. Haven't formally tested, but from what I've seen, raw html renders faster and more fluidly than javascript-generated html cross-browser. Plus, I'm not sure how mobile devices handle dynamic html performance-wise. Testing. I have a lot of integration tests that work well with static HTML, so switching to javascript-only would require 1) more focused pure-javascript testing (jasmine), and 2) integrating javascript into capybara integration tests. This is just a matter of time and work, but it's probably significant. Maintenance. Getting rid of HAML. I love HAML, it's so easy to write, it prints pretty HTML... It makes code clean, it makes maintenance easy. Going with javascript, there's nothing as concise. SEO. I know google handles the ajax /#!/path, but haven't grasped how this will affect other search engines and how older browsers handle it. Seems like it'd require a significant setup.

  Read the article

< Previous Page | 19 20 21 22 23 24 25  | Next Page >