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  • Raspberry Pi Now Shipping with 512MB RAM; Still Only $35

    - by Jason Fitzpatrick
    Fans of the tiny Raspberry Pi will be pleased to hear the new version of their Model B board now ships with 512MB of RAM (up from the previous 256MB). The best part about the upgrade? The price point stays at $35 a board. From the official Raspberry Pi blog: One of the most common suggestions we’ve heard since launch is that we should produce a more expensive “Model C” version of Raspberry Pi with extra RAM. This would be useful for people who want to use the Pi as a general-purpose computer, with multiple large applications running concurrently, and would enable some interesting embedded use cases (particularly using Java) which are slightly too heavyweight to fit comfortably in 256MB. The downside of this suggestion for us is that we’re very attached to $35 as our highest price point. With this in mind, we’re pleased to announce that from today all Model B Raspberry Pis will ship with 512MB of RAM as standard. If you have an outstanding order with either distributor, you will receive the upgraded device in place of the 256MB version you ordered. Units should start arriving in customers’ hands today, and we will be making a firmware upgrade available in the next couple of days to enable access to the additional memory. We’re excited to get our hands on a new board and try out Raspbmc with that extra RAM. HTG Explains: What is the Windows Page File and Should You Disable It? How To Get a Better Wireless Signal and Reduce Wireless Network Interference How To Troubleshoot Internet Connection Problems

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  • How to prevent duplicate data access methods that retrieve similar data?

    - by Ronald Wildenberg
    In almost every project I work on with a team, the same problem seems to creep in. Someone writes UI code that needs data and writes a data access method: AssetDto GetAssetById(int assetId) A week later someone else is working on another part of the application and also needs an AssetDto but now including 'approvers' and writes the following: AssetDto GetAssetWithApproversById(int assetId) A month later someone needs an asset but now including the 'questions' (or the 'owners' or the 'running requests', etc): AssetDto GetAssetWithQuestionsById(int assetId) AssetDto GetAssetWithOwnersById(int assetId) AssetDto GetAssetWithRunningRequestsById(int assetId) And it gets even worse when methods like GetAssetWithOwnerAndQuestionsById start to appear. You see the pattern that emerges: an object is attached to a large object graph and you need different parts of this graph in different locations. Of course, I'd like to prevent having a large number of methods that do almost the same. Is it simply a matter of team discipline or is there some pattern I can use to prevent this? In some cases it might make sense to have separate methods, i.e. getting an asset with running requests may be expensive so I do not want to include these all the time. How to handle such cases?

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  • How do I keep controversy in check?

    - by Aaron Digulla
    This is probably OT but it's less OT here than on any other SO site, so please bear with me. I'm working on a new project votEm. The goal is to give independent candidates a platform to introduce themselves to get elected for a political office. My main reason is that today, it's too expensive to run for an office. Some politicians in the US spend as much as 30 million dollars (!) for a single campaign. That money is better spent elsewhere. In a similar fashion, people who want to change countries like Egypt, could use such a platform to present themselves. Now I expect a lot of emotions and pressure on my site. People with a lot of money (and a lot to lose) will try to game it (political parties, secret services of ... errr ... "not 100% democratic countries", big companies, ...) To avoid as many mistakes as possible, I need a list of resources, ideas and tips how to keep such a site out of too much trouble. PS: I'd make this CW but the option seems to be gone...

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  • Can too much abstraction be bad?

    - by m3th0dman
    As programmers I feel that our goal is to provide good abstractions on the given domain model and business logic. But where should this abstraction stop? How to make the trade-off between abstraction and all it's benefits (flexibility, ease of changing etc.) and ease of understanding the code and all it's benefits. I believe I tend to write code overly abstracted and I don't know how good is it; I often tend to write it like it is some kind of a micro-framework, which consists of two parts: Micro-Modules which are hooked up in the micro-framework: these modules are easy to be understood, developed and maintained as single units. This code basically represents the code that actually does the functional stuff, described in requirements. Connecting code; now here I believe stands the problem. This code tends to be complicated because it is sometimes very abstracted and is hard to be understood at the beginning; this arises due to the fact that it is only pure abstraction, the base in reality and business logic being performed in the code presented 1; from this reason this code is not expected to be changed once tested. Is this a good approach at programming? That it, having changing code very fragmented in many modules and very easy to be understood and non-changing code very complex from the abstraction POV? Should all the code be uniformly complex (that is code 1 more complex and interlinked and code 2 more simple) so that anybody looking through it can understand it in a reasonable amount of time but change is expensive or the solution presented above is good, where "changing code" is very easy to be understood, debugged, changed and "linking code" is kind of difficult. Note: this is not about code readability! Both code at 1 and 2 is readable, but code at 2 comes with more complex abstractions while code 1 comes with simple abstractions.

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  • How to determine the amount to spend per phrase on Adwords research?

    - by Anonymous -
    My company would like to start a PPC advertising campaign. Whilst I understand the concept and how to set everything up from a technical point of view, this is something I've never done before. Logically, we'd like to test out a wide range of keywords that we think would lead to conversions, which we've put together through brainstorming and with some help from Google's External Keyword Tool. Sub-question whilst I remember - am I correct in thinking that in Google's keyword tool, keywords that we think will perform well that have a low competition yet high monthly searches are good since there will be less advertisers, meaning our bid per click will be less? Is there a common benchmark or process of doing a round of tests with keywords? Should we wait for 100 clicks on each keyword, see which ones have lead to the most sales (or rather, sales that are sustainable with the cost per click of that keyword), then drop the ones which aren't converting and put that budget onto the converting keywords? We realistically have a few hundred keywords/phrases we would like to test, but spending $100 per keyword/phrase is going to work out as quite an expensive test. It would be nice to be able to spend $5-10 per phrase, but I don't think the sample size would be great enough to determine anything usefully reliable. Another approach might be to setup all the keywords, and those that bring the most sales within x hours/days would be the ones we use. What is the common procedure with things like this? I know there are a plethora of companies that specialize in exactly this, but this is something we anticipate doing a lot in the future, so it would make sense to do it in house if at all possible.

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  • WebCenter at Oracle Day Toronto

    - by Lance Shaw
    The Oracle Day event took place in Toronto yesterday at the Hyatt Regency Hotel downtown.  Attendance was excellent and it was standing room only at the keynote sessions.   Anytime the venue has to bring in chairs to handle the overflow crowd, you know there is a lot of interest! This year, WebCenter was featured prominently as part of the Fusion Middleware session track.  What was interesting to see was just how many customers are interested in consolidating and simplifying their existing infrastructure.  So many companies are still struggling with information silos such as file shares, SharePoint Sites and a myriad of departmental or process-centric repositories.  Naturally, these get more and more expensive to manage over time so there is a high level of interest in reducing the size, scope and cost of this infrastructure.  When companies see how they can use Fusion Middleware and related technologies to integrate with WebCenter Content, Imaging and other solutions to centralize content delivery across business applications, they quickly realize that there are significant cost savings to be had. Oracle Day Events are happening all over the world and there is likely going to be one near you.  To check out the full list and to register, visit the Event page here.  It is a great way to not only hear about WebCenter and how it can be used to your advantage, but also a great way to learn about the broader set of related products in the Fusion Middleware portfolio that are available to extend and enhance the power of your particular business solutions. If you cannot make it, or missed the event in your area, be sure to visit our new WebCenter Content page with a variety of informative assets all in one simple location.  It's a new page designed to provide you with easy access to customer stories, videos, whitepapers, webcasts and more.  We hope you find it valuable!

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  • The Mac Tax

    - by Robert May
    One of our users was having difficulties with their mac and using some web software.  I decided to go peruse the landscape and see how much of a premium people were paying for their macs.  I priced out a Dell and a Mac from their websites.  I tried to get them as close to the same configuration, from a hardware standpoint, as I could.  I found the following: Apple Macbook Pro   Dell XPS 17 There are several important differences in the hardware: The mac doesn’t have a blueray player, but the dell does. The mac has a slightly slower processor. The mac claims to have a better battery, but doesn’t list the specifics, so there’s no way to tell. The mac doesn’t list the video card stats, so there’s no way to tell how comparable they are, but they’re probably close. The mac doesn’t come with any additional software.  No iWorks, iPhoto, etc.  They were left to their default of None, so arguably, the Dell is more functional out of the box. Other than changing the hardware specs to be close, all other configuration options were left at their default. So riddle me this, Batman:  Why do people buy Macs?  I have several dev buddies that own them, but I can’t justify the cost.  First, most of them load bootcamp and/or parallels at extra cost to run windows 7 and windows apps.  The hardware isn’t as good.  The price is almost twice as expensive. How do you justify the premium price? Technorati Tags: General

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  • Does LINQ require significantly more processing cycles and memory than lower-level data iteration techniques?

    - by Matthew Patrick Cashatt
    Background I am recently in the process of enduring grueling tech interviews for positions that use the .NET stack, some of which include silly questions like this one, and some questions that are more valid. I recently came across an issue that may be valid but I want to check with the community here to be sure. When asked by an interviewer how I would count the frequency of words in a text document and rank the results, I answered that I would Use a stream object put the text file in memory as a string. Split the string into an array on spaces while ignoring punctuation. Use LINQ against the array to .GroupBy() and .Count(), then OrderBy() said count. I got this answer wrong for two reasons: Streaming an entire text file into memory could be disasterous. What if it was an entire encyclopedia? Instead I should stream one block at a time and begin building a hash table. LINQ is too expensive and requires too many processing cycles. I should have built a hash table instead and, for each iteration, only added a word to the hash table if it didn't otherwise exist and then increment it's count. The first reason seems, well, reasonable. But the second gives me more pause. I thought that one of the selling points of LINQ is that it simply abstracts away lower-level operations like hash tables but that, under the veil, it is still the same implementation. Question Aside from a few additional processing cycles to call any abstracted methods, does LINQ require significantly more processing cycles to accomplish a given data iteration task than a lower-level task (such as building a hash table) would?

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  • Flow Fields in Dynamics NAV

    - by T
    I don’t know the exact business reason but someone asked how to identify all sales shipping orders with any negative quantities on them.  They needed to print these separately from the shipments that only have all positive quantities. Here is one way to solve this problem In NAV, open Sales Shipment Header Add a field of type Boolean (The field type should match the value you expect to return from the flow field method.  In this case we will use an exist so we expect a bool but we could have used a Sum, Average, Min, Max, Count, or a Lookup to return a value). Define it as a flow field and click on the ellipse next to CalcFormula Now [Has Negative Qty] is false if no negatives exist And [Has Negative Qty] and true if a negative exist So it is ready to be used as a filter on the report. Don’t forget that if you are using it in code, you may need to CalcFields. Hope that helps.  If you really can’t afford the field in your header, you can use code to check the lines for a negative value each time and use a skip or break function to skip that header record but it seems expensive to check them all if you only want a few to print. Please let me know if you think of a better solution.

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  • Is there really anything to gain with complex design? [duplicate]

    - by SB2055
    This question already has an answer here: What is enterprise software, exactly? 8 answers I've been working for a consulting firm for some time, with clients of various sizes, and I've seen web applications ranging in complexity from really simple: MVC Service Layer EF DB To really complex: MVC UoW DI / IoC Repository Service UI Tests Unit Tests Integration Tests But on both ends of the spectrum, the quality requirements are about the same. In simple projects, new devs / consultants can hop on, make changes, and contribute immediately, without having to wade through 6 layers of abstraction to understand what's going on, or risking misunderstanding some complex abstraction and costing down the line. In all cases, there was never a need to actually make code swappable or reusable - and the tests were never actually maintained past the first iteration because requirements changed, it was too time-consuming, deadlines, business pressure, etc etc. So if - in the end - testing and interfaces aren't used rapid development (read: cost-savings) is a priority the project's requirements will be changing a lot while in development ...would it be wrong to recommend a super-simple architecture, even to solve a complex problem, for an enterprise client? Is it complexity that defines enterprise solutions, or is it the reliability, # concurrent users, ease-of-maintenance, or all of the above? I know this is a very vague question, and any answer wouldn't apply to all cases, but I'm interested in hearing from devs / consultants that have been in the business for a while and that have worked with these varying degrees of complexity, to hear if the cool-but-expensive abstractions are worth the overall cost, at least while the project is in development.

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  • Automated Qt testing framework

    - by user1457565
    Can someone recommend a good robust "Free" testing framework for Qt? Our requirements: Should be able to test basic mouse click / mouse move events SHould be able to handle non-widget view components Should have "record" capability to generate test scripts. Should be automatable for running it daily. We looked at: Squish - this solves all our problems. But it is just too da** expensive. KD Executor - the download page now links to the squish page and says thats what they recommend for testing. Not sure what they mean by that. TDriver - from nokia.qt. Super difficult to install. Very little documentation. Having a hard time to just install. I wonder how much harder it would be to write tests. qtestlib - Could not handle non-widget components. Everything has to be a widget to be tested. No "record" feature. Can someone help with any other alternative ? thanks Mouli

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  • Cry Engine 3 vs UDK

    - by Daniele Riccardelli
    I'm new here and I hope that other people may find this question interesting. Me and a bunch of guys from my University are thinking about getting started in game development, but, even though the game design is kind of ready, we are stucked at the point "which Engine should we choose". At first, we were thinking about Unity3D Free, in particular because we are pretty familiar with C# and, even better, it's completely free, but on the other hand there are some cons like no dynamic shadowing that make the realization of our game kinda hard. So, we are thinking about moving either to UDK or Cry Engine, since they are not as expensive as Unity3D Pro (at least before the game deployment) . The thing we are worried the most, though, is that we are kind of scared about the support for team work(i mean, that we might find it hard to coordinate our efforts without software support), since in Unity3D the team features are part of purchasable content, and we are not interested in paying that much for a project we are not even sure we can complete. So, finally, I hope one of you knows the mentioned engines enough to give us a tip telling which one offers better team features and is advisable for guys that have barely worked before on videogames but have good object oriented programming skills. Probably might be helpful for your suggestion, if i say that our game is an exploration game. Thanks to anybody who's going to answer.

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  • Neural network input preprocessing

    - by TND
    It's clear that the effectiveness of a neural network depends strongly on the format you give it to work with. You want to preprocess it into the most convenient form you can algorithmically get to, so that the neural network doesn't have to account for that itself. I'm working on a little project that (surprise!) is going to be using neural networks. My future goal is to eventually use NEAT, which I'm really excited about. Anyway, one of my ideas involves moving entities in continuous 2D space, from a top-down perspective (this would be a really cool game AI). Of course, unless these guys are blind, they're going to be able to see the world around them. There's a lot of different ways this information could be fed into the network. One interesting but expensive way is to simply render a top-down "view" of things, with the entities as dots on the picture, and feed that in. I was hoping for something much simpler to use (at least at first), such as a list of the x (maybe 7 or so) nearest entities and their position in relative polar coordinates, orientation, health, etc., but I'm trying to think of the best way to do it. My first instinct was to order them by distance, which would inherently also train the neural network to consider those more "important". However, I was thinking- what if there's two entities that are nearly the same distance away? They could easily alternate indexes in that list, confusing the network. My question is, is there a better way of representing this? Essentially, the issue is the network needs a good way of keeping track of who's who, while knowing (by being inputted) relevant information about the list of entities it can see. Thanks!

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  • How can state changes be batched while adhering to opaque-front-to-back/alpha-blended-back-to-front?

    - by Sion Sheevok
    This is a question I've never been able to find the answer to. Batching objects with similar states is a major performance gain when rendering many objects. However, I've been learned various rules when drawing objects in the game world. Draw all opaque objects, front-to-back. Draw all alpha-blended objects, back-to-front. Some of the major parameters to batch by, as I understand it, are textures, vertex buffers, and index buffers. It seems that, as long as you are adhering to the above two rules, there's little to be done in regards to batching. I see one possibility to batch, while still adhering to the above two rules. Opaque objects can still be drawn out of depth-order, because drawing them front-to-back is merely a fillrate optimization, meanwhile state changes may very well be far more expensive than the overdraw of drawing out of depth-order. However, non-opaque objects, those that require alpha-blending at least, must be drawn back-to-front in order to avoid rendering artifacts. Is the loss of the fillrate optimization for opaques worth the state batching optimization?

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  • Testing a codebase with sequential cohesion

    - by iveqy
    I've this really simple program written in C with ncurses that's basically a front-end to sqlite3. I would like to implement TDD to continue the development and have found a nice C unit framework for this. However I'm totally stuck on how to implement it. Take this case for example: A user types a letter 'l' that is captured by ncurses getch(), and then an sqlite3 query is run that for every row calls a callback function. This callback function prints stuff to the screen via ncurses. So the obvious way to fully test this is to simulate a keyboard and a terminal and make sure that the output is the expected. However this sounds too complicated. I was thinking about adding an abstraction layer between the database and the UI so that the callback function will populate a list of entries and that list will later be printed. In that case I would be able to check if that list contains the expected values. However, why would I struggle with a data structure and lists in my program when sqlite3 already does this? For example, if the user wants to see the list sorted in some other way, it would be expensive to throw away the list and repopulate it. I would need to sort the list, but why should I implement sorting when sqlite3 already has that? Using my orginal design I could just do an other query sorted differently. Previously I've only done TDD with command line applications, and there it's really easy to just compare the output with what I'm expected. An other way would be to add CLI interface to the program and wrap a test program around the CLI to test everything. (The way git.git does with it's test-framework). So the question is, how to add testing to a tightly integrated database/UI.

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  • Is Moving Entity Framework objects over a webservice really the best way?

    - by aceinthehole
    I've inherited a .NET project that has close to 2 thousand clients out in the field that need to push data periodically up to a central repository. The clients wake up and attempt to push the data up via a series of WCF webservices where they are passing each entity framework entity as parameter. Once the service receives this object, it preforms some business logic on the data, and then turns around and sticks it in it's own database that mirrors the database on the client machines. The trick is, is that this data is being transmitted over a metered connection, which is very expensive. So optimizing the data is a serious priority. Now, we are using a custom encoder that compresses the data (and decompresses it on the other end) while it is being transmitted, and this is reducing the data footprint. However, the amount of data that the clients are using, seem ridiculously large, given the amount of information that is actually being transmitted. It seems me that entity framework itself may be to blame. I'm suspecting that the objects are very large when serialized to be sent over wire, with a lot context information and who knows what else, when what we really need is just the 'new' inserts. Is using the entity framework and WCF services as we have done so far the correct way, architecturally, of approaching this n-tiered, asynchronous, push only problem? Or is there a different approach, that could optimize the data use?

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  • What are solutions and tradeoffs to maintain search result consistency in a web application

    - by iammichael
    Consider a web application with a custom search function that must display the results in a paged manner (twenty per page with up to hundreds of thousands of total results) and the ability to drill down to individual results that maintain next/previous links to navigate through the results. Re-executing the search on each page request to get the appropriate results for that page of data can be too expensive (up to 15s per search). Also, since the underlying data can change frequently (e.g. addition of new results), re-executing could cause the next/previous functionality to result in inconsistent behavior (e.g. the same results reappearing on a later page after having been viewed on an earlier page). What options exist to ensure the search results can be viewed across multiple pages in a consistent manner, and what tradeoffs does each option have in terms of network, CPU, memory, and storage requirements? EDIT: I thought caching the query search results was an obvious necessity. The question is really asking about where to cache the result set and what tradeoffs might exist to each. For example, storing the ids of the entities in the result set on the client, or storing the IDs of the entities themselves in the users session on the web server, or in a temporary table in the database. I'm not looking specifically for a single solution as different scenarios may result in different approaches (and such a question would be more suited for stackoverflow.com rather than here), but more of a design comparison between the possible approaches.

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  • Amazon EC2 vs Dedicated server at Hetzner, what's the use for EC2?

    - by C-Blu
    After searching the web I still can't find the reason to use EC2. What's the point to scale EC2? If you expect a huge burst in traffic, they say. OK, but what if you already have a couple of sites with good traffic, and for example medium reserved EC2 instance is not enough. You are paying $36.60(medium reserved for 1year) in EU(Ireland) + traffic + optional expenses for databases and S3 if you use them. Of course as some point when you are under $56.6-$66.1 you can optimize your hosting costs with Amazon EC2. But when you get at some point if purchase EX4 server from Hetzner, it will surpass your perfomance needs for a long time, before you get a massive traffic. (I am wrong?) CPU: i7-2600 Quadcore (3.4-3.8 Ghz) RAM: 16 GB HDD: 2x3 TB SATA (6 Gbit/s) - I think that disc performance of a dedicated is better then of Amazon EBS Traffic: 10 TiB in month included. This is what you get from Hetzner for $56(- 19% VAT) or $66 for EU residents. Please, tell me what's the reason to use Amazon? Which load won't a server from Hetzner take, but Amazon Auto Scaling will? The maintenance of dedicated vs EC2 is still the same? Or hardware failure at Amazon, won't ruin your EBS storage? I'm still not at the level when I need expensive hosting, but want to know beforehand, just to be sure if Amazon infrastructure is better then pure performance of Hetzner's hardware.

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  • Search multiple tables

    - by gilden
    I have developed a web application that is used mainly for archiving all sorts of textual material (documents, references to articles, books, magazines etc.). There can be any given number of archive tables in my system, each with its own schema. The schema can be changed by a moderator through the application (imagine something similar to a really dumbed down version of phpMyAdmin). Users can search for anything from all of the tables. By using FULLTEXT indexes together with substring searching (fields which do not support FULLTEXT indexing) the script inserts the results of a search to a single table and by ordering these results by the similarity measure I can fairly easily return the paginated results. However, this approach has a few problems: substring searching can only count exact results the 50% rule applies to all tables separately and thus, mysql may not return important matches or too naively discards common words. is quite expensive in terms of query numbers and execution time (not an issue right now as there's not a lot of data yet in the tables). normalized data is not even searched for (I have different tables for categories, languages and file attatchments). My planned solution Create a single table having columns similar to id, table_id, row_id, data Every time a new row is created/modified/deleted in any of the data tables this central table also gets updated with the data column containing a concatenation of all the fields in a row. I could then create a single index for Sphinx and use it for doing searches instead. Are there any more efficient solutions or best practises how to approach this? Thanks.

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  • Form development optimization

    - by Juan
    Like many web developers I do forms all the time. I found myself doing the same all the time: placing input fields, assigning a name to each, ajax the form, then create the PHP which involves to assign a PHP var to each $_REQUEST['var'], escape and validate data, build the html and emailing the results. So I found that 70% of the work is duplicated but I just can't duplicate a page and change the fields. I end up wasting more time reformatting, deleting and adding different fields than creating from scratch. I started planing to program a "list of IDs to html+php" converter in which I'd input all the IDs and this would output the basic html and php. Then I thought: there's got to be thousands of developers that go through this, I'd be reinventing the wheel. So this is my question, I'm trying to find that wheel that somebody must have invented already. I found this: http://www.trirand.com/blog/jqform/ which does more or less what I'm looking for but it's an expensive solution and it has too much functionality for what I'd be using it. Which tools do you use to optimize repetitive task about HTML and PHP?

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  • Spending a good fortune on a certificate holding Scrum Master or a Veteran XP coach?

    - by ashy_32bit
    There is a very prestigious company that delivers a well-sold software about financial systems. It has more that 20 years of history, and is staffed with about 20 programmers and much larger number of managerial staff. Dissatisfied customers have reported strange bugs and no one has a clue what is wrong, hard to read code, and customization is prohibitively expensive. In a word, the software is rotten. The company decided to spend a fortune and found the Agile thing as the remedy but they are stuck about what it is they need most urgently. Is it about the process or the developers or both? The challenge breaks down to the following options: They can hire a certificate holding Scrum Master to teach them Scrum. When asked about the value of doing it, the SM responded: "I will prepare them to embrace Agile and only then they can go Agile and save the product". They can as well hire a veteran XP coach. When posed with the same question he responded : "The most urgent problem is with the programmers and not the management, XP will save the product from rot and only then Scrum will make sense" Developers are far from capable of doing agile programming practices at the moment. No unit tests, no pair programmings, no CI (huh? what is it?) ... you get the idea. Some say they would be far better trying to improve their programming first (hire option 2) and then go with the process. Many say quite the opposite. Any insights ?

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  • Advice needed on Process - Service Design

    - by user99314
    Need some advice from experts on designing a flow. Create a service that will read a csv file which may contain anywhere over 6000+ rows of individual ids as shown in the sample below. Need to read that file and go to oracle database and fetch a vname,vnumber,vid of each id in the csv and then go to document repository i.e. Oracle UCM and download all documents matching vname,vnumber,vid there can be =0 documents for each vname,vnumber,vid and save them on a file system. UCM exposes a webservice to dowload the documents. Finally create a new csv appending the filenames that are downloaded for each id. Need to keep track of any errors but need to make sure to go over the whole ids in the csv to download the documents and skip in case of errors. Need some advice on how to go about designing this as there may be over 6000+ rows in a csv file and looping it and hitting the database for each individual id and then hitting a UCM may be a bit expensive so open for any idea. How to go by designing this solution. Wondering if messaging can be helpful here or offloading process of getting the vname,vnumber,vid to pl/sql packages, creating staging tables etc. Initial csv that contains ids: **ID** 12345a 12s345 3456fr we9795 we9797 Final csv output: **ID Files Downloaded from UCM** 12345a a.pdf,b.doc,d.txt 12s345 a1.pdf,s2.pdf,f4.gif 3456fr b.xls we9795 we9797 x.doc Thanks

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  • Server Setups for Agencies [closed]

    - by styks1987
    We are considering consolidating our server administration by cutting down on the number of systems we currently use to manage all our websites(~65 websites). Currently we have a testing server and 3 production servers. (2 - cherokee(linode), 1 - apache (mt)) We don't have a dedicated server admin, so I am stuck with managing all these servers, and as a developer, I don't want to deal with all the server hassle. So my main goal is to cut down on the time spent messing with the servers. We have looked at Pagoda Box and AppFog as possibilities. I am not sure if Pagoda Box would be cost effective. With 65+ websites we may end up paying anywhere from 0 to $50+ per website per month. Right now we page about $250 per month for the 4 VPS servers mentioned above. We already use Capistrano for deployment. I have the opportunity to completely overhaul the entire setup and I would like some feedback on where you found your information for large scale server management or how you currently do it. Articles are welcome. In summary: What is new (past 2 years) in simple server management arena? If you work at an agency or have had agency experience, how do/did you manage your sites? a. What is the level of effort for SSL, new site setup, database management, and extension management. b. How did you handle datacenter outages. Anyone with Pagoda Box experience, do you like it and did you have problems with Wordpress, Cakephp, Drupal, Expression Engine or Magento? a. Is it expensive for you? b. How has server uptime been? Your direction and comments are greatly appreciated.

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  • Load and Web Performance Testing using Visual Studio Ultimate 2010-Part 3

    - by Tarun Arora
    Welcome back once again, in Part 1 of Load and Web Performance Testing using Visual Studio 2010 I talked about why Performance Testing the application is important, the test tools available in Visual Studio Ultimate 2010 and various test rig topologies, in Part 2 of Load and Web Performance Testing using Visual Studio 2010 I discussed the details of web performance & load tests as well as why it’s important to follow a goal based pattern while performance testing your application. In part 3 I’ll be discussing Test Result Analysis, Test Result Drill through, Test Report Generation, Test Run Comparison, Asp.net Profiler and some closing thoughts. Test Results – I see some creepy worms! In Part 2 we put together a web performance test and a load test, lets run the test to see load test to see how the Web site responds to the load simulation. While the load test is running you will be able to see close to real time analysis in the Load Test Analyser window. You can use the Load Test Analyser to conduct load test analysis in three ways: Monitor a running load test - A condensed set of the performance counter data is maintained in memory. To prevent the results memory requirements from growing unbounded, up to 200 samples for each performance counter are maintained. This includes 100 evenly spaced samples that span the current elapsed time of the run and the most recent 100 samples.         After the load test run is completed - The test controller spools all collected performance counter data to a database while the test is running. Additional data, such as timing details and error details, is loaded into the database when the test completes. The performance data for a completed test is loaded from the database and analysed by the Load Test Analyser. Below you can see a screen shot of the summary view, this provides key results in a format that is compact and easy to read. You can also print the load test summary, this is generated after the test has completed or been stopped.         Analyse the load test results of a previously run load test – We’ll see this in the section where i discuss comparison between two test runs. The performance counters can be plotted on the graphs. You also have the option to highlight a selected part of the test and view details, drill down to the user activity chart where you can hover over to see more details of the test run.   Generate Report => Test Run Comparisons The level of reports you can generate using the Load Test Analyser is astonishing. You have the option to create excel reports and conduct side by side analysis of two test results or to track trend analysis. The tools also allows you to export the graph data either to MS Excel or to a CSV file. You can view the ASP.NET profiler report to conduct further analysis as well. View Data and Diagnostic Attachments opens the Choose Diagnostic Data Adapter Attachment dialog box to select an adapter to analyse the result type. For example, you can select an IntelliTrace adapter, click OK and open the IntelliTrace summary for the test agent that was used in the load test.   Compare results This creates a set of reports that compares the data from two load test results using tables and bar charts. I have taken these screen shots from the MSDN documentation, I would highly recommend exploring the wealth of knowledge available on MSDN. Leaving Thoughts While load testing the application with an excessive load for a longer duration of time, i managed to bring the IIS to its knees by piling up a huge queue of requests waiting to be processed. This clearly means that the IIS had run out of threads as all the threads were busy processing existing request, one easy way of fixing this is by increasing the default number of allocated threads, but this might escalate the problem. The better suggestion is to try and drill down to the actual root cause of the problem. When ever the garbage collection runs it stops processing any pages so all requests that come in during that period are queued up, but realistically the garbage collection completes in fraction of a a second. To understand this better lets look at the .net heap, it is divided into large heap and small heap, anything greater than 85kB in size will be allocated to the Large object heap, the Large object heap is non compacting and remember large objects are expensive to move around, so if you are allocating something in the large object heap, make sure that you really need it! The small object heap on the other hand is divided into generations, so all objects that are supposed to be short-lived are suppose to live in Gen-0 and the long living objects eventually move to Gen-2 as garbage collection goes through.  As you can see in the picture below all < 85 KB size objects are first assigned to Gen-0, when Gen-0 fills up and a new object comes in and finds Gen-0 full, the garbage collection process is started, the process checks for all the dead objects and assigns them as the valid candidate for deletion to free up memory and promotes all the remaining objects in Gen-0 to Gen-1. So in the future when ever you clean up Gen-1 you have to clean up Gen-0 as well. When you fill up Gen – 0 again, all of Gen – 1 dead objects are drenched and rest are moved to Gen-2 and Gen-0 objects are moved to Gen-1 to free up Gen-0, but by this time your Garbage collection process has started to take much more time than it usually takes. Now as I mentioned earlier when garbage collection is being run all page requests that come in during that period are queued up. Does this explain why possibly page requests are getting queued up, apart from this it could also be the case that you are waiting for a long running database process to complete.      Lets explore the heap a bit more… What is really a case of crisis is when the objects are living long enough to make it to Gen-2 and then dying, this is definitely a high cost operation. But sometimes you need objects in memory, for example when you cache data you hold on to the objects because you need to use them right across the user session, which is acceptable. But if you wanted to see what extreme caching can do to your server then write a simple application that chucks in a lot of data in cache, run a load test over it for about 10-15 minutes, forcing a lot of data in memory causing the heap to run out of memory. If you get to such a state where you start running out of memory the IIS as a mode of recovery restarts the worker process. It is great way to free up all your memory in the heap but this would clear the cache. The problem with this is if the customer had 10 items in their shopping basket and that data was stored in the application cache, the user basket will now be empty forcing them either to get frustrated and go to a competitor website or if the customer is really patient, give it another try! How can you address this, well two ways of addressing this; 1. Workaround – A x86 bit processor only allows a maximum of 4GB of RAM, this means the machine effectively has around 3.4 GB of RAM available, the OS needs about 1.5 GB of RAM to run efficiently, the IIS and .net framework also need their share of memory, leaving you a heap of around 800 MB to play with. Because Team builds by default build your application in ‘Compile as any mode’ it means the application is build such that it will run in x86 bit mode if run on a x86 bit processor and run in a x64 bit mode if run on a x64 but processor. The problem with this is not all applications are really x64 bit compatible specially if you are using com objects or external libraries. So, as a quick win if you compiled your application in x86 bit mode by changing the compile as any selection to compile as x86 in the team build, you will be able to run your application on a x64 bit machine in x86 bit mode (WOW – By running Windows on Windows) and what that means is, you could use 8GB+ worth of RAM, if you take away everything else your application will roughly get a heap size of at least 4 GB to play with, which is immense. If you need a heap size of more than 4 GB you have either build a software for NASA or there is something fundamentally wrong in your application. 2. Solution – Now that you have put a workaround in place the IIS will not restart the worker process that regularly, which means you can take a breather and start working to get to the root cause of this memory leak. But this begs a question “How do I Identify possible memory leaks in my application?” Well i won’t say that there is one single tool that can tell you where the memory leak is, but trust me, ‘Performance Profiling’ is a great start point, it definitely gets you started in the right direction, let’s have a look at how. Performance Wizard - Start the Performance Wizard and select Instrumentation, this lets you measure function call counts and timings. Before running the performance session right click the performance session settings and chose properties from the context menu to bring up the Performance session properties page and as shown in the screen shot below, check the check boxes in the group ‘.NET memory profiling collection’ namely ‘Collect .NET object allocation information’ and ‘Also collect the .NET Object lifetime information’.    Now if you fire off the profiling session on your pages you will notice that the results allows you to view ‘Object Lifetime’ which shows you the number of objects that made it to Gen-0, Gen-1, Gen-2, Large heap, etc. Another great feature about the profile is that if your application has > 5% cases where objects die right after making to the Gen-2 storage a threshold alert is generated to alert you. Since you have the option to also view the most expensive methods and by capturing the IntelliTrace data you can drill in to narrow down to the line of code that is the root cause of the problem. Well now that we have seen how crucial memory management is and how easy Visual Studio Ultimate 2010 makes it for us to identify and reproduce the problem with the best of breed tools in the product. Caching One of the main ways to improve performance is Caching. Which basically means you tell the web server that instead of going to the database for each request you keep the data in the webserver and when the user asks for it you serve it from the webserver itself. BUT that can have consequences! Let’s look at some code, trust me caching code is not very intuitive, I define a cache key for almost all searches made through the common search page and cache the results. The approach works fine, first time i get the data from the database and second time data is served from the cache, significant performance improvement, EXCEPT when two users try to do the same operation and run into each other. But it is easy to handle this by adding the lock as you can see in the snippet below. So, as long as a user comes in and finds that the cache is empty, the user locks and starts to get the cache no more concurrency issues. But lets say you are processing 10 requests per second, by the time i have locked the operation to get the results from the database, 9 other users came in and found that the cache key is null so after i have come out and populated the cache they will still go in to get the results again. The application will still be faster because the next set of 10 users and so on would continue to get data from the cache. BUT if we added another null check after locking to build the cache and before actual call to the db then the 9 users who follow me would not make the extra trip to the database at all and that would really increase the performance, but didn’t i say that the code won’t be very intuitive, may be you should leave a comment you don’t want another developer to come in and think what a fresher why is he checking for the cache key null twice !!! The downside of caching is, you are storing the data outside of the database and the data could be wrong because the updates applied to the database would make the data cached at the web server out of sync. So, how do you invalidate the cache? Well if you only had one way of updating the data lets say only one entry point to the data update you can write some logic to say that every time new data is entered set the cache object to null. But this approach will not work as soon as you have several ways of feeding data to the system or your system is scaled out across a farm of web servers. The perfect solution to this is Micro Caching which means you cache the query for a set time duration and invalidate the cache after that set duration. The advantage is every time the user queries for that data with in the time span for which you have cached the results there are no calls made to the database and the data is served right from the server which makes the response immensely quick. Now figuring out the appropriate time span for which you micro cache the query results really depends on the application. Lets say your website gets 10 requests per second, if you retain the cache results for even 1 minute you will have immense performance gains. You would reduce 90% hits to the database for searching. Ever wondered why when you go to e-bookers.com or xpedia.com or yatra.com to book a flight and you click on the book button because the fare seems too exciting and you get an error message telling you that the fare is not valid any more. Yes, exactly => That is a cache failure! These travel sites or price compare engines are not going to hit the database every time you hit the compare button instead the results will be served from the cache, because the query results are micro cached, its a perfect trade-off, by micro caching the results the site gains 100% performance benefits but every once in a while annoys a customer because the fare has expired. But the trade off works in the favour of these sites as they are still able to process up to 30+ page requests per second which means cater to the site traffic by may be losing 1 customer every once in a while to a competitor who is also using a similar caching technique what are the odds that the user will not come back to their site sooner or later? Recap   Resources Below are some Key resource you might like to review. I would highly recommend the documentation, walkthroughs and videos available on MSDN. You can always make use of Fiddler to debug Web Performance Tests. Some community test extensions and plug ins available on Codeplex might also be of interest to you. The Road Ahead Thank you for taking the time out and reading this blog post, you may also want to read Part I and Part II if you haven’t so far. If you enjoyed the post, remember to subscribe to http://feeds.feedburner.com/TarunArora. Questions/Feedback/Suggestions, etc please leave a comment. Next ‘Load Testing in the cloud’, I’ll be working on exploring the possibilities of running Test controller/Agents in the Cloud. See you on the other side! Thank You!   Share this post : CodeProject

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  • Sorting Algorithms

    - by MarkPearl
    General Every time I go back to university I find myself wading through sorting algorithms and their implementation in C++. Up to now I haven’t really appreciated their true value. However as I discovered this last week with Dictionaries in C# – having a knowledge of some basic programming principles can greatly improve the performance of a system and make one think twice about how to tackle a problem. I’m going to cover briefly in this post the following: Selection Sort Insertion Sort Shellsort Quicksort Mergesort Heapsort (not complete) Selection Sort Array based selection sort is a simple approach to sorting an unsorted array. Simply put, it repeats two basic steps to achieve a sorted collection. It starts with a collection of data and repeatedly parses it, each time sorting out one element and reducing the size of the next iteration of parsed data by one. So the first iteration would go something like this… Go through the entire array of data and find the lowest value Place the value at the front of the array The second iteration would go something like this… Go through the array from position two (position one has already been sorted with the smallest value) and find the next lowest value in the array. Place the value at the second position in the array This process would be completed until the entire array had been sorted. A positive about selection sort is that it does not make many item movements. In fact, in a worst case scenario every items is only moved once. Selection sort is however a comparison intensive sort. If you had 10 items in a collection, just to parse the collection you would have 10+9+8+7+6+5+4+3+2=54 comparisons to sort regardless of how sorted the collection was to start with. If you think about it, if you applied selection sort to a collection already sorted, you would still perform relatively the same number of iterations as if it was not sorted at all. Many of the following algorithms try and reduce the number of comparisons if the list is already sorted – leaving one with a best case and worst case scenario for comparisons. Likewise different approaches have different levels of item movement. Depending on what is more expensive, one may give priority to one approach compared to another based on what is more expensive, a comparison or a item move. Insertion Sort Insertion sort tries to reduce the number of key comparisons it performs compared to selection sort by not “doing anything” if things are sorted. Assume you had an collection of numbers in the following order… 10 18 25 30 23 17 45 35 There are 8 elements in the list. If we were to start at the front of the list – 10 18 25 & 30 are already sorted. Element 5 (23) however is smaller than element 4 (30) and so needs to be repositioned. We do this by copying the value at element 5 to a temporary holder, and then begin shifting the elements before it up one. So… Element 5 would be copied to a temporary holder 10 18 25 30 23 17 45 35 – T 23 Element 4 would shift to Element 5 10 18 25 30 30 17 45 35 – T 23 Element 3 would shift to Element 4 10 18 25 25 30 17 45 35 – T 23 Element 2 (18) is smaller than the temporary holder so we put the temporary holder value into Element 3. 10 18 23 25 30 17 45 35 – T 23   We now have a sorted list up to element 6. And so we would repeat the same process by moving element 6 to a temporary value and then shifting everything up by one from element 2 to element 5. As you can see, one major setback for this technique is the shifting values up one – this is because up to now we have been considering the collection to be an array. If however the collection was a linked list, we would not need to shift values up, but merely remove the link from the unsorted value and “reinsert” it in a sorted position. Which would reduce the number of transactions performed on the collection. So.. Insertion sort seems to perform better than selection sort – however an implementation is slightly more complicated. This is typical with most sorting algorithms – generally, greater performance leads to greater complexity. Also, insertion sort performs better if a collection of data is already sorted. If for instance you were handed a sorted collection of size n, then only n number of comparisons would need to be performed to verify that it is sorted. It’s important to note that insertion sort (array based) performs a number item moves – every time an item is “out of place” several items before it get shifted up. Shellsort – Diminishing Increment Sort So up to now we have covered Selection Sort & Insertion Sort. Selection Sort makes many comparisons and insertion sort (with an array) has the potential of making many item movements. Shellsort is an approach that takes the normal insertion sort and tries to reduce the number of item movements. In Shellsort, elements in a collection are viewed as sub-collections of a particular size. Each sub-collection is sorted so that the elements that are far apart move closer to their final position. Suppose we had a collection of 15 elements… 10 20 15 45 36 48 7 60 18 50 2 19 43 30 55 First we may view the collection as 7 sub-collections and sort each sublist, lets say at intervals of 7 10 60 55 – 20 18 – 15 50 – 45 2 – 36 19 – 48 43 – 7 30 10 55 60 – 18 20 – 15 50 – 2 45 – 19 36 – 43 48 – 7 30 (Sorted) We then sort each sublist at a smaller inter – lets say 4 10 55 60 18 – 20 15 50 2 – 45 19 36 43 – 48 7 30 10 18 55 60 – 2 15 20 50 – 19 36 43 45 – 7 30 48 (Sorted) We then sort elements at a distance of 1 (i.e. we apply a normal insertion sort) 10 18 55 60 2 15 20 50 19 36 43 45 7 30 48 2 7 10 15 18 19 20 30 36 43 45 48 50 55 (Sorted) The important thing with shellsort is deciding on the increment sequence of each sub-collection. From what I can tell, there isn’t any definitive method and depending on the order of your elements, different increment sequences may perform better than others. There are however certain increment sequences that you may want to avoid. An even based increment sequence (e.g. 2 4 8 16 32 …) should typically be avoided because it does not allow for even elements to be compared with odd elements until the final sort phase – which in a way would negate many of the benefits of using sub-collections. The performance on the number of comparisons and item movements of Shellsort is hard to determine, however it is considered to be considerably better than the normal insertion sort. Quicksort Quicksort uses a divide and conquer approach to sort a collection of items. The collection is divided into two sub-collections – and the two sub-collections are sorted and combined into one list in such a way that the combined list is sorted. The algorithm is in general pseudo code below… Divide the collection into two sub-collections Quicksort the lower sub-collection Quicksort the upper sub-collection Combine the lower & upper sub-collection together As hinted at above, quicksort uses recursion in its implementation. The real trick with quicksort is to get the lower and upper sub-collections to be of equal size. The size of a sub-collection is determined by what value the pivot is. Once a pivot is determined, one would partition to sub-collections and then repeat the process on each sub collection until you reach the base case. With quicksort, the work is done when dividing the sub-collections into lower & upper collections. The actual combining of the lower & upper sub-collections at the end is relatively simple since every element in the lower sub-collection is smaller than the smallest element in the upper sub-collection. Mergesort With quicksort, the average-case complexity was O(nlog2n) however the worst case complexity was still O(N*N). Mergesort improves on quicksort by always having a complexity of O(nlog2n) regardless of the best or worst case. So how does it do this? Mergesort makes use of the divide and conquer approach to partition a collection into two sub-collections. It then sorts each sub-collection and combines the sorted sub-collections into one sorted collection. The general algorithm for mergesort is as follows… Divide the collection into two sub-collections Mergesort the first sub-collection Mergesort the second sub-collection Merge the first sub-collection and the second sub-collection As you can see.. it still pretty much looks like quicksort – so lets see where it differs… Firstly, mergesort differs from quicksort in how it partitions the sub-collections. Instead of having a pivot – merge sort partitions each sub-collection based on size so that the first and second sub-collection of relatively the same size. This dividing keeps getting repeated until the sub-collections are the size of a single element. If a sub-collection is one element in size – it is now sorted! So the trick is how do we put all these sub-collections together so that they maintain their sorted order. Sorted sub-collections are merged into a sorted collection by comparing the elements of the sub-collection and then adjusting the sorted collection. Lets have a look at a few examples… Assume 2 sub-collections with 1 element each 10 & 20 Compare the first element of the first sub-collection with the first element of the second sub-collection. Take the smallest of the two and place it as the first element in the sorted collection. In this scenario 10 is smaller than 20 so 10 is taken from sub-collection 1 leaving that sub-collection empty, which means by default the next smallest element is in sub-collection 2 (20). So the sorted collection would be 10 20 Lets assume 2 sub-collections with 2 elements each 10 20 & 15 19 So… again we would Compare 10 with 15 – 10 is the winner so we add it to our sorted collection (10) leaving us with 20 & 15 19 Compare 20 with 15 – 15 is the winner so we add it to our sorted collection (10 15) leaving us with 20 & 19 Compare 20 with 19 – 19 is the winner so we add it to our sorted collection (10 15 19) leaving us with 20 & _ 20 is by default the winner so our sorted collection is 10 15 19 20. Make sense? Heapsort (still needs to be completed) So by now I am tired of sorting algorithms and trying to remember why they were so important. I think every year I go through this stuff I wonder to myself why are we made to learn about selection sort and insertion sort if they are so bad – why didn’t we just skip to Mergesort & Quicksort. I guess the only explanation I have for this is that sometimes you learn things so that you can implement them in future – and other times you learn things so that you know it isn’t the best way of implementing things and that you don’t need to implement it in future. Anyhow… luckily this is going to be the last one of my sorts for today. The first step in heapsort is to convert a collection of data into a heap. After the data is converted into a heap, sorting begins… So what is the definition of a heap? If we have to convert a collection of data into a heap, how do we know when it is a heap and when it is not? The definition of a heap is as follows: A heap is a list in which each element contains a key, such that the key in the element at position k in the list is at least as large as the key in the element at position 2k +1 (if it exists) and 2k + 2 (if it exists). Does that make sense? At first glance I’m thinking what the heck??? But then after re-reading my notes I see that we are doing something different – up to now we have really looked at data as an array or sequential collection of data that we need to sort – a heap represents data in a slightly different way – although the data is stored in a sequential collection, for a sequential collection of data to be in a valid heap – it is “semi sorted”. Let me try and explain a bit further with an example… Example 1 of Potential Heap Data Assume we had a collection of numbers as follows 1[1] 2[2] 3[3] 4[4] 5[5] 6[6] For this to be a valid heap element with value of 1 at position [1] needs to be greater or equal to the element at position [3] (2k +1) and position [4] (2k +2). So in the above example, the collection of numbers is not in a valid heap. Example 2 of Potential Heap Data Lets look at another collection of numbers as follows 6[1] 5[2] 4[3] 3[4] 2[5] 1[6] Is this a valid heap? Well… element with the value 6 at position 1 must be greater or equal to the element at position [3] and position [4]. Is 6 > 4 and 6 > 3? Yes it is. Lets look at element 5 as position 2. It must be greater than the values at [4] & [5]. Is 5 > 3 and 5 > 2? Yes it is. If you continued to examine this second collection of data you would find that it is in a valid heap based on the definition of a heap.

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