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• Flash SWF not initializing until visible - can I force them to initialize?

  - by Jason

  I have an application that needs to render about 100 flash graphs (as well as other DOM stuff) in a series of rows that vertically extend many times beyond the current visible window - in other words, the users have to scroll down see see all the different graphs. This application is also dynamic and when a user changes a value in the DOM (anywhere on the page) it will need to propagate that change to all the Flash graphs at the same time. So I setup all the externalInterface callbacks and was careful to not let any JS start going until the ever-so-important "flashIsReady" call and...it worked great until I tried to update() the existing swf's with new data. Here was the behavior: - All the swfs load (initially) in both IE/Fox = good. - Updating swfs with new content works in IE but not in Fox = not good - Updating swfs with new content works in Fox --ONLY IF-- I scrolled down to the bottom of the page, then back to the top -- BEFORE -- I triggered an update(). So then I started tracing out each time a swf called the JS to say "flash is ready" and I realized, Firfox only renders swfs as they become visible. And To be honest - that's fine and actually, I am pretty sure that IE does this too. But the problem is that not only does Firefox not initialize the swf, Firefox doesn't even acknowledge the swf exists (expect for after onload) if it has not yet been visible. And the proof is that you get JS errors saying: "[FlashDOMID].FlashMethod is not a function". However, scroll down a little, wait until its visible and suddenly the trace starts lighting up "Flash Ready", "Flash Ready", "Flash Ready" and once they are all ready, everything works fine. Someone told me that FF does not init swf's until visible - can I force it? I can post code if you need...but its pretty heavy (hard to strip out the relevant from the rest) and I would like to avoid it (for your sakes) if possible. The question is simple - have you had this happen and if so, did you find a solution? Does anyone now how to force a not-yet-visible swf to initialize? Thanks guys.

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• Database structure for ecommerce site

  - by imanc

  Hey Guys, I have been tasked with designing an ecommerce solution. The aspect that is causing me the most problems is the database. Currently the site consists of 10+ country based shops each with their own database (all residing on the same mysql instance). For the new site I'd rather all these shop databases be merged into one database so that all tables (products, orders, customers etc.) have a shop_id field. From a programming perspective this seems to make the most sense as we won't have to manage data across multiple databases. Currently the entire site generates about 120k orders a year, but is experiencing fairly heavy growth and we need to design a solution that will scale. In 5 years there may be more than a million orders per year and a database that contains 5 years order history (archiving maybe a solution here). The question is - do we use a single database, or do we keep the database-per-shop structure? I am currently trying to find supporting evidence for either avenue. The company I am designing the solution for prefer the per-shop database structure because they believe it will allow the sites to scale. But my argument is that the shop's database probably won't get that busy over the next few years that they exceed the capacity of a mysql database and a "no expenses spared" hardware set-up. I am wondering if anyone has any advice either way? Does anyone have experience with websites / ecommerce sites that have tables containing millions of records? I know there is probably not a clear answer here, but at what stage do we have too many records or too large table files to have a fast loading site? Also, if anyone has any advice on sources of information - books, websites, etc. where I can do further research, it would be highly appreciated! Cheers, imanc

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• How to enter text into the "Write something..." box on Facebook and click Submit

  - by Peter Payne

  Hello, I am trying to manipulate Facebook pages in various ways, using Javascript browser elements. I'd need to be able to insert some text into the top "Type something..." box that shows on my site's fan page (or alternately, "click into" the field and I can type the text using GUI scripting), then click the "submit" button as if i'd done it by hand. It's tricky since the page is very Ajax heavy and I can't find the names of the elements I need to manipulate, let alone how to manipulate them as they're not using traditional form fields I'm used to. Can anyone help me figure out how to do this with javascript commands, which I'd be calling from Applescript on the Mac? Many thanks in advance. UPDATE Thanks for the comments below. Believe me, I am not trying to do anything spammy or douchy, mainly posting links to products that have gone live on page facebook page, but do it during the business day when people are on rather than at strange hours of the day. I am located in Japan so my sleep period is right when people are using FB. The solution I came up with for clicking the button was got using UI Browser, an outstanding tool if you're trying to script on the Mac. The script that clicked the button for me was: tell application "Safari" activate set thename to name of (get current tab of window 1) delay 3 tell application "System Events" tell process "Safari" try click button "Share" of group 1 of group 2 of list 3 of group 9 of UI element 1 of scroll area 1 of group 3 of window thename -- this one works on the mini? on error click button "Share" of group 1 of group 2 of list 3 of group 9 of UI element 1 of scroll area 1 of group 2 of window thename -- did not work end try end tell end tell end tell Hope this is useful to anyone.

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• Programming exercises in Java inheritance for intern

  - by Tenner

  I work for a small software development team, working primarily in Java, for a very large company. Our new intern showed up sight-unseen (not uncommon in my company). He has some C++ experience but no Java. Worse, he's never worked with inheritance in C++. Our code has a great deal of abstraction and a heavy reliance on inheritance. We need to get him up to speed as quickly as possible. Of course the rest of the team is busy, and so we can't take the time out of our day to teach a one-student 200-level CS course. Instead, I'd like to give him an actual programming project to work on which highlights how classes, interfaces, method overrides, etc. work. I've had him look at Project Euler, but most of the solutions end up being procedural, and not object-oriented programs. Do any of you have any somewhat-straightforward (and relatively quick) projects which you would give to an intern in this situation? Or, any recent (or current) students have a school project they'd be willing to share? Anyone else had this experience?

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• Travelling Visual Studio developers

  - by Graphain

  Hi, I am about to travel to Europe (I'm Australian but imagine this is a similar circumstance for US users and simply flipped for European users). However, there is the slim possibility I will need to do some Visual Studio work while I'm travelling. As I see it I have three options: Leave a desktop PC on at home, access remotely via net cafes. Carry a laptop with me on the trip, upload files as required using public wifi. Option 2 but instead buy cheap light netbook that is miraculously capable of running VS. Does anyone have any experience or advice to shed on any of these options? For reference, this existing post suggests that VS remotely for short distances is okay, but over longer distances could be more problematic. I've used VS via RDP to a US server before and it was pretty laggy but for small changes I could get by. Concerns I have that you may have some experience with: Weight of luggage (ideally like to travel light) Security of laptop (imagine it'll be too heavy to carry around all the time so have to leave it at hotel/hostel etc. and hope for the best) Security of data (don't want someone stealing RDP access to my home PC) Security of FTP (don't want someone stealing FTP passwords over wireless)

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• Database schema for Product Properties

  - by Chemosh

  As so many people I'm looking for a Products /Product Properties database schema. I'm using Ruby on Rails and (Thinking) Sphinx for faceted searches. Requirements: Adding new product types and their options should not require a change to the database schema Support faceted searches using Sphinx. Solutions I've come across: (See Bill Karwin's answer) Option 1: Single Table Inheritance Not an option really. The table would contain way to many columns. Option 2: Class Table Inheritance Ruby on Rails caches the database schema on start-up which means a restart whenever a new type of product is introduced. If you have a size able product catalog this could mean hundreds of tables. Option 3: Serialized LOB Kills being able to do faceted searches without heavy application logic. Option 4: Entity-Attribute-Value For testing purposes, EAV worked fine. However it could quickly become a mess and a maintenance hell as you add more and more options (e.g. when an option increase the prices or delivery time). What option should I go with? What other solutions are out there? Is there a silver bullet (ha) I overlooked?

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• Python: Does one of these examples waste more memory?

  - by orokusaki

  In a Django view function which uses manual transaction committing, I have: context = RequestContext(request, data) transaction.commit() return render_to_response('basic.html', data, context) # Returns a Django ``HttpResponse`` object which is similar to a dictionary. I think it is a better idea to do this: context = RequestContext(request, data) response = render_to_response('basic.html', data, context) transaction.commit() return response If the page isn't rendered correctly in the second version, the transaction is rolled back. This seems like the logical way of doing it albeit there won't likely be many exceptions at that point in the function when the application is in production. But... I fear that this might cost more and this will be replete through a number of functions since the application is heavy with custom transaction handling, so now is the time to figure out. If the HttpResponse instance is in memory already (at the point of render_to_response()), then what does another reference cost? When the function ends, doesn't the reference (response variable) go away so that when Django is done converting the HttpResponse into a string for output Python can immediately garbage collect it? Is there any reason I would want to use the first version (other than "It's 1 less line of code.")?

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• How to insert zeros between bits in a bitmap?

  - by anatolyg

  I have some performance-heavy code that performs bit manipulations. It can be reduced to the following well-defined problem: Given a 13-bit bitmap, construct a 26-bit bitmap that contains the original bits spaced at even positions. To illustrate: 0000000000000000000abcdefghijklm (input, 32 bits) 0000000a0b0c0d0e0f0g0h0i0j0k0l0m (output, 32 bits) I currently have it implemented in the following way in C: if (input & (1 << 12)) output |= 1 << 24; if (input & (1 << 11)) output |= 1 << 22; if (input & (1 << 10)) output |= 1 << 20; ... My compiler (MS Visual Studio) turned this into the following: test eax,1000h jne 0064F5EC or edx,1000000h ... (repeated 13 times with minor differences in constants) I wonder whether i can make it any faster. I would like to have my code written in C, but switching to assembly language is possible. Can i use some MMX/SSE instructions to process all bits at once? Maybe i can use multiplication? (multiply by 0x11111111 or some other magical constant) Would it be better to use condition-set instruction (SETcc) instead of conditional-jump instruction? If yes, how can i make the compiler produce such code for me? Any other idea how to make it faster? Any idea how to do the inverse bitmap transformation (i have to implement it too, bit it's less critical)?

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• MSMQ - Message Queue Abstraction and Pattern

  - by Maxim Gershkovich

  Hi All, Let me define the problem first and why a messagequeue has been chosen. I have a datalayer that will be transactional and EXTREMELY insert heavy and rather then attempt to deal with these issues when they occur I am hoping to implement my application from the ground up with this in mind. I have decided to tackle this problem by using the Microsoft Message Queue and perform inserts as time permits asynchronously. However I quickly ran into a problem. Certain inserts that I perform may need to be recalled (ie: retrieved) immediately (imagine this is for POS system and what happens if you need to recall the last transaction - one that still hasn’t been inserted). The way I decided to tackle this problem is by abstracting the MessageQueue and combining it in my data access layer thereby creating the illusion of a single set of data being returned to the user of the datalayer (I have considered the other issues that occur in such a scenario (ie: essentially dirty reads and such) and have concluded for my purposes I can control these issues). However this is where things get a little nasty... I’ve worked out how to get the messages back and such (trivial enough problem) but where I am stuck is; how do I create a generic (or at least somewhat generic) way of querying my message queue? One where I can minimize the duplication between the SQL queries and MessageQueue queries. I have considered using LINQ (but have very limited understanding of the technology) and have also attempted an implementation with Predicates which so far is pretty smelly. Are there any patterns for such a problem that I can utilize? Am I going about this the wrong way? Does anyone have an of their own ideas about how I can tackle this problem? Does anyone even understand what I am talking about? :-) Any and ALL input would be highly appreciated and seriously considered… Thanks again.

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• Architecture for database analytics

  - by David Cournapeau

  Hi, We have an architecture where we provide each customer Business Intelligence-like services for their website (internet merchant). Now, I need to analyze those data internally (for algorithmic improvement, performance tracking, etc...) and those are potentially quite heavy: we have up to millions of rows / customer / day, and I may want to know how many queries we had in the last month, weekly compared, etc... that is the order of billions entries if not more. The way it is currently done is quite standard: daily scripts which scan the databases, and generate big CSV files. I don't like this solutions for several reasons: as typical with those kinds of scripts, they fall into the write-once and never-touched-again category tracking things in "real-time" is necessary (we have separate toolset to query the last few hours ATM). this is slow and non-"agile" Although I have some experience in dealing with huge datasets for scientific usage, I am a complete beginner as far as traditional RDBM go. It seems that using column-oriented database for analytics could be a solution (the analytics don't need most of the data we have in the app database), but I would like to know what other options are available for this kind of issues.

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• How to split up levels? (cocos2d,box2d,iphone) to save CPU and memory?

  - by cocos2dbeginner

  Hi, so I'm going to create large levels. But there's a problem: There's much unseen space (it's a jump'n run like mario bros.) and this will use memory + cpu. so how could I split up my levels? I'm using Box2D+ cocos2d for iphone. Any ideas? Mayby just set the visible property to NO? But it would be still in the memory :(. But what with the box2d bodies? Destroy and recreate them would be to heavy for the FPS, because I have physics built in which should not be recreated. Should I make fix points where i want to split the level up, than if the player is 200 px away it should preload it. and if the player is 200 px away from the last part of the level I unload it. But there would be the problem with the physics, because on the start of the level it has a unique movement and later if i destroy and recreate it it would do the same. but i don't want that. other ideas?

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• What is the appropriate HTML 5 element for a hero unit/showcase?

  - by deb

  A lot of marketing and content-heavy sites showcase the page's primary content using large text and/or images, sometimes with a slider, containing a call to action for signing up for a service, or downloading an app, etc.. I'm not sure what this design element is called, I got the term hero unit from twitter bootstrap: http://twitter.github.com/bootstrap/components.html#typography I think most of you know what I'm trying to describe... If it's not clear I can add screenshots or links to this question. I looked at a few different sites, and some put this hero unit inside a ASIDE element, others use SECTION, ARTICLE and even HEADER. Using twitter bootstrap as an example again: <header class="jumbotron masthead"> <div class="inner"> <h1>Bootstrap, from Twitter</h1> <p>Simple and flexible HTML, CSS, and Javascript for popular user interface components and interactions.</p> <p class="download-info"> Is HEADER the most appropriate tag for this type of content? Or should I use ASIDE, ARTICLE or SECTION?

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• Java Input/Output streams for unnamed pipes created in native code?

  - by finrod

  Is there a way to easily create Java Input/Output streams for unnamed pipes created in native code? Motivation: I need my own implementation of the Process class. The native code spawns me a new process with subprocess' IO streams redirected to unnamed pipes. Problem: The file descriptors for correct ends of those pipes make their way to Java. At this point I get stuck as I cannot create a new FileDescriptor which I could pass to FileInput/FileOutput stream. I have used reflection to get around the problem and got communication with a simple bouncer sub-process running. However I have a notion that it is not the cleanest way to go. Have you used this approach? Do you see any problems with this approach? (the platform will never change) Searching around the internets revealed similar solution using native code. Any thoughts before I dive into heavy testing of this approach are very welcome. I would like to give a shot to existing code before writing my own IO stream implementations... Thank you.

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• Modelling in Agile Development

  - by bertzzie

  I'm writing a bachelor dissertation report where I'm developing a system with Agile methodology. Given that the development is an one man show, of course the "Agile" I did was not really agile at all (from my understanding at least). So I want some perspective from SO crowds, who is of course a professional, real world, developer with tons of experience. I think real world experience is better than the theory and experiments that I did. My question is: Do we model during development time when using Agile? UML? DFD? Or a Functional Specification is enough1? If modelling is not really necessary, what do we use to communicate to the user, as the user almost always won't understand UML or DFD? For my system, I use UI & UX Design with heavy prototyping, but then I don't have time to draw UML any more. Which one is better? 1 http://www.joelonsoftware.com/articles/fog0000000036.html I hope the question's not "subjective and argumentative" as I know this question exist because of my lack of understanding in the agile development. If it is, could someone just give me a pointer or reference about that? Possible duplicate: Do you use UML in Agile development practices?

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• .NET MVC: How to fix Visual Studio's lack of awareness of CSS classes in partial views?

  - by Mega Matt

  Hi all, This has been sort of an annoyance for me for a while. I make pretty heavy use of partial views in MVC, and am using Visual Studio 2008 to develop. The problem is that when I give html elements a class in a partial view (<div class="someClass">), it will underline them in green like it doesn't know what they are. I realize this is because I'm in a partial view, and haven't put link tags anywhere in that file for it to know where the CSS is (the link tags are in the main view that renders the partial view). The CSS still works fine on my site because the browser will render all views as one long html page anyway, but it's really annoying to look through my partial views and see all of my classes underlined in green. Is there a way that I can still tell Visual Studio that those classes exist somewhere, from the partial view? I figured there has to be a way to let it know, but am not sure what it is. Maybe a way to import the stylesheets from the parent view? Thanks for your help.

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• In SQL Server what is most efficient way to compare records to other records for duplicates with in

  - by Glenn

  We have an SQL Server that gets daily imports of data files from clients. This data is interrelated and we are always scrubbing it and having to look for suspect duplicate records between these files. Finding and tagging suspect records can get pretty complicated. We use logic that requires some field values to be the same, allows some field values to differ, and allows a range to be specified for how different certain field values can be. The only way we've found to do it is by using a cursor based process, and it places a heavy burden on the database. So I wanted to ask if there's a more efficient way to do this. I've heard it said that there's almost always a more efficient way to replace cursors with clever JOINS. But I have to admit I'm having a lot of trouble with this one. For a concrete example suppose we have 1 table, an "orders" table, with the following 6 fields. order_id, customer_id product_id, quantity, sale_date, price We want to look through the records to find suspect duplicates on the following example criteria. These get increasingly harder. 1. Records that have the same product_id, sale_date, and quantity but different customer_id's should be marked as suspect duplicates for review. 2. Records that have the same customer_id, product_id, quantity and have sale_dates within five days of each other should be marked as suspect duplicates for review 3. Records that have the same customer_id, product_id, but different quantities within 20 units, and sales dates within five days of each other should be considered suspect. Is it possible to satisfy each one of these criteria with a single SQL Query that uses JOINS? Is this the most efficient way to do this?

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• How do i set the Transaction Isolation in EJB?

  - by Nitesh Panchal

  Hello, I am not able to find a way to set TransactionIsolation in ejb. Can anybody tell me how do i set it? I am using persistence. I have looked the following classes : EntityManager , EntityManagerFactory, UserTransaction. None of them seems to have any method like setTransactionIsolation or such. Do we need to change persistence.xml? I just read a book named Mastering EJB 3.0 4th edition. They gave a full 10 page theory about Isolation level that this problems occur and that occurs and such things but at the end they gave this paragraph :- "As we now know, the EJB standard does not deal with isolation levels directly, and rightly so. EJB is a component specification. It defines the behavior and contracts of a business component with clients and middleware infrastructure (containers) such that the component can be rendered as various middleware services properly. EJBs therefore are transactional components that interact with resource managers, such as the JDBC resource manager or JMS resource manager, via JTS, as part of a transaction. They are not, hence, resource components in themselves. Since isolation levels are very specific to the behavior and capabilities of the underlying resources, they should therefore be specified at the resource API levels. " What exactly does it mean? What is meant by resource level APIs? Please help me. If persistence has no way to set Isolation Level then why do they give such huge theory in an EJB book and make it heavy in weight unnecessarily :(

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• send email to list of users with different timezones?

  - by ylazez

  i use the following method to send email to list of users i want the (To) in each email to be for just the user only not all users i.e appears to the users that the email is sent to only him my guess is to loop on: message.addRecipients(Message.RecipientType.TO, address); then send the message right? , but this is a heavy process sending an email many times any ideas ? suppose that i have the timezone for each user and i want to send each user the message in his timzone, the same issue i guess setting sent date for each user in his timezone then sending the message, right ? the method is: try { Properties props = System.getProperties(); props.put("mail.smtp.host", "localhost"); // Get a mail session Session session = Session.getDefaultInstance(props, null); // Define a new mail message Message message = new MimeMessage(session); InternetAddress ia = new InternetAddress(); ia.setPersonal("MySite"); ia.setAddress(from); message.setFrom(ia); Address[] address = new Address[recievers.size()]; for (int i = 0; i < recievers.size(); i++) { address[i] = new InternetAddress(recievers.get(i)); } message.addRecipients(Message.RecipientType.TO, address); message.setSubject(subject); // Create a message part to represent the body text BodyPart messageBodyPart = new MimeBodyPart(); messageBodyPart.setContent(body, "text/html"); // use a MimeMultipart as we need to handle the file attachments Multipart multipart = new MimeMultipart(); // add the message body to the mime message multipart.addBodyPart(messageBodyPart); // Put all message parts in the message message.setContent(multipart); message.setSentDate(getCurrentDate()); // Send the message Transport.send(message); } catch (Exception ex) {}

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• "Finding" an object instance of a known class?

  - by Sean C

  My first post here (anywhere for that matter!), re. Cocoa/Obj-C (I'm NOT up to speed on either, please be patient!). I hope I haven't missed the answer already, I did try to find it. I'm an old-school procedural dog (haven't done any programming since the mid 80's, so I probably just can't even learn new tricks), but OOP has my head spinning! My question is: is there any means at all to "discover/find/identify" an instance of an object of a known class, given that some OTHER unknown process instantiated it? eg. somthing that would accomplish this scenario: (id) anObj = [someTarget getMostRecentInstanceOf:[aKnownClass class]]; for that matter, "getAnyInstance" or "getAllInstances" might do the trick too. Background: I'm trying to write a plugin for a commercial application, so much of the heavy lifting is being done by the app, behind the scenes. I have the SDK & header files, I know what class the object is, and what method I need to call (it has only instance methods), I just can't identify the object for targetting. I've spent untold hours and days going over Apples documentation, tutorials and lots of example/sample code on the web (including here at Stack Overflow), and come up empty. Seems that everything requires a known target object to work, and I just don't have one. Since I may not be expressing my problem as clearly as needed, I've put up a web page, with diagram & working sample pages to illustrate: http://www.nulltime.com/svtest/index.html Any help or guidance will be appreciated! Thanks.

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• How to test if a user has SELECTED a file to upload ?

  - by Tristan

  Hello, on a page, i have : if (!empty($_FILES['logo']['name'])) { $dossier = 'upload/'; $fichier = basename($_FILES['logo']['name']); $taille_maxi = 100000; $taille = filesize($_FILES['logo']['tmp_name']); $extensions = array('.png', '.jpg', '.jpeg'); $extension = strrchr($_FILES['logo']['name'], '.'); if(!in_array($extension, $extensions)) { $erreur = 'ERROR you must upload the right type'; } if($taille>$taille_maxi) { $erreur = 'too heavy'; } if(!empty($erreur)) { ....................... } The problem is, if the users wants to edit information WITHOUT uploading a LOGO, it raises an error : 'error you must upload the right type' So, if a user didn't put anything in the inputbox in order to upload it, i don't want to enter in these conditions test. i tested : if (!empty($_FILES['logo']['name']) and if (isset($_FILES['logo']['name']) but both doesn't seems to work. Any ideas? edit : maybe i wasn't so clear, i don't want to test if he uploaded a logo, i want to test IF he selected a file to upload, because right now, if he doesn't select a file to upload, php raises an error telling he must upload with the right format. thanks.

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• ASP.Net Session Storage provider in 3-layer architecture

  - by Tedd Hansen

  I'm implementing a custom session storage provider in ASP.Net. We have a strict 3-layer architecture and therefore the session storage needs to go through the business layer. Presentation-Business-Database. The business layer is accessed through WPF. The database is MSSQL. What I need is (in order of preference): A commercial/free/open source product that solves this. The source code of a SqlSessionStateStore (custom session store) (not the ODBC-sample on MSDN) that I can modify to use a middle layer. I've tried looking at .Net source through Reflector, but the code is not usable. Note: I understand how to do this. I am looking for working samples, preferably that has been proven to work fine under heavy load. The ODBC sample on MSDN doesn't use the (new?) stored procs that the build in SqlSessionStateStore uses - I'd like to use these if possible (decreases traffic). Edit1: To answer Simons question on more info: ASP.Net Session()-object can be stored in either InProc, ASP.Net State Service or SQL-server. In a secure 3-layer model the presentation layer (web server) does not have direct/physical access to the database layer (SQL-server). And even without the physical limitations, from an architectural standpoint you may not want this. InProc and ASP.Net State Service does not support load balancing and doesn't have fault tolerance. Therefore the only option is to access SQL through webservice middle layer (business layer).

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• Reduce durability in MySQL for performance

  - by Paul Prescod

  My site occasionally has fairly predictable bursts of traffic that increase the throughput by 100 times more than normal. For example, we are going to be featured on a television show, and I expect in the hour after the show, I'll get more than 100 times more traffic than normal. My understanding is that MySQL (InnoDB) generally keeps my data in a bunch of different places: RAM Buffers commitlog binary log actual tables All of the above places on my DB slave This is too much "durability" given that I'm on an EC2 node and most of the stuff goes across the same network pipe (file systems are network attached). Plus the drives are just slow. The data is not high value and I'd rather take a small chance of a few minutes of data loss rather than have a high probability of an outage when the crowd arrives. During these traffic bursts I would like to do all of that I/O only if I can afford it. I'd like to just keep as much in RAM as possible (I have a fair chunk of RAM compared to the data size that would be touched over an hour). If buffers get scarce, or the I/O channel is not too overloaded, then sure, I'd like things to go to the commitlog or binary log to be sent to the slave. If, and only if, the I/O channel is not overloaded, I'd like to write back to the actual tables. In other words, I'd like MySQL/InnoDB to use a "write back" cache algorithm rather than a "write through" cache algorithm. Can I convince it to do that? If this is not possible, I am interested in general MySQL write-performance optimization tips. Most of the docs are about optimizing read performance, but when I get a crowd of users, I am creating accounts for all of them, so that's a write-heavy workload.

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• Rendering maps from raw SVG data in Java

  - by Lunikon

  In an application of mine I have to display locations and great circle paths in a map which is rendered to PNG and then displayed on the web. For this I simply use a world map (NASA's Blue Marbel in fact) scaled to various "zoom levels" as base image and only display the a part of it matching the final image size and fitting all items to be displayed. Straight forward so far. Now I came across Wikipedia's awesome blank SVG maps which contain all the country codes for easy reference and I was wondering whether it was possible to use those to have more customized colors and to highliht countries etc. So I did a bit of googling and was looking for Java libraries which would enable me to load the blank SVG map to memory allows for easy reference/selection of certain paths do manipulations of coloring, stroke widths etc render to a buffered image as the background for the great-circle paths/nodes What I came across quite often was Batik, but it looks like a really heavy framework and I'm not quite sure whether it is what I'm looking for. I have recently played around with Raphaël a bit and I like the way it handles working with vector graphics in code. If the Java framework for my purpose would feature a similar interface, that would be a nice-to-have. Any recommendations what toolset would be approriate for my purposes?

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• Multithreaded linked list traversal

  - by Rob Bryce

  Given a (doubly) linked list of objects (C++), I have an operation that I would like multithread, to perform on each object. The cost of the operation is not uniform for each object. The linked list is the preferred storage for this set of objects for a variety of reasons. The 1st element in each object is the pointer to the next object; the 2nd element is the previous object in the list. I have solved the problem by building an array of nodes, and applying OpenMP. This gave decent performance. I then switched to my own threading routines (based off Windows primitives) and by using InterlockedIncrement() (acting on the index into the array), I can achieve higher overall CPU utilization and faster through-put. Essentially, the threads work by "leap-frog'ing" along the elements. My next approach to optimization is to try to eliminate creating/reusing the array of elements in my linked list. However, I'd like to continue with this "leap-frog" approach and somehow use some nonexistent routine that could be called "InterlockedCompareDereference" - to atomically compare against NULL (end of list) and conditionally dereference & store, returning the dereferenced value. I don't think InterlockedCompareExchangePointer() will work since I cannot atomically dereference the pointer and call this Interlocked() method. I've done some reading and others are suggesting critical sections or spin-locks. Critical sections seem heavy-weight here. I'm tempted to try spin-locks but I thought I'd first pose the question here and ask what other people are doing. I'm not convinced that the InterlockedCompareExchangePointer() method itself could be used like a spin-lock. Then one also has to consider acquire/release/fence semantics... Ideas? Thanks!

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• Recommendations for IPC between parent and child processes in .NET?

  - by Jeremy

  My .NET program needs to run an algorithm that makes heavy use of 3rd party libraries (32-bit), most of which are unmanaged code. I want to drive the CPU as hard as I can, so the code runs several threads in parallel to divide up the work. I find that running all these threads simultaneously results in temporary memory spikes, causing the process' virtual memory size to approach the 2 GB limit. This memory is released back pretty quickly, but occasionally if enough threads enter the wrong sections of code at once, the process crosses the "red line" and either the unmanaged code or the .NET code encounters an out of memory error. I can throttle back the number of threads but then my CPU usage is not as high as I would like. I am thinking of creating worker processes rather than worker threads to help avoid the out of memory errors, since doing so would give each thread of execution its own 2 GB of virtual address space (my box has lots of RAM). I am wondering what are the best/easiest methods to communicate the input and output between the processes in .NET? The file system is an obvious choice. I am used to shared memory, named pipes, and such from my UNIX background. Is there a Windows or .NET specific mechanism I should use?

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