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• What FIX implementation do you recommend for use with .NET

  - by Ajaxx

  I am reviewing implementation choices for FIX when using .NET. A few obvious choices come to mind, but I want to know if there are other options, better choices or if we've made the same decision as a lot of you. QuickFIX - Stable, C++ implementation - so you've got unmanaged code to interop with. FIX4NET - C# implementation - seems to have some gaps in its implementation. DIY - Chime in here if you've made your own FIX engine Let me throw in some caveats here. I'm not looking for sub 100 microsecond processing. Performance is a requirement, but not so much that it's driving my decisions. A solid product that is stable, performs well and is flexible enough to deal with vendor specific dialects is the sweet spot. The more we can do in .NET the better.

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• CakePHP repeats same queries

  - by Rytis

  I have a model structure: Category hasMany Product hasMany Stockitem belongsTo Warehouse, Manufacturer. I fetch data with this code, using containable to be able to filter deeper in the associated models: $this->Category->find('all', array( 'conditions' => array('Category.id' => $category_id), 'contain' => array( 'Product' => array( 'Stockitem' => array( 'conditions' => array('Stockitem.warehouse_id' => $warehouse_id), 'Warehouse', 'Manufacturer', ) ) ), ) ); Data structure is returned just fine, however, I get multiple repeating queries like, sometimes hundreds of such queries in a row, based on dataset. SELECT `Warehouse`.`id`, `Warehouse`.`title` FROM `beta_warehouses` AS `Warehouse` WHERE `Warehouse`.`id` = 2 Basically, when building data structure Cake is fetching data from mysql over and over again, for each row. We have datasets of several thousand rows, and I have a feeling that it's going to impact performance. Is it possible to make it cache results and not repeat same queries?

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• How do I calculate a good hash code for a list of strings?

  - by Ian Ringrose

  Background: I have a short list of strings. The number of strings is not always the same, but are nearly always of the order of a “handful” In our database will store these strings in a 2nd normalised table These strings are never changed once they are written to the database. We wish to be able to match on these strings quickly in a query without the performance hit of doing lots of joins. So I am thinking of storing a hash code of all these strings in the main table and including it in our index, so the joins are only processed by the database when the hash code matches. So how do I get a good hashcode? I could: Xor the hash codes of all the string together Xor with multiply the result after each string (say by 31) Cat all the string together then get the hashcode Some other way So what do people think? (If you care we are using .NET and SqlServer)

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• Which is the best API/Library to use when accessing a WebCam in .Net?

  - by Doctor Jones

  Which is the best API to use when accessing a WebCam in .Net? (I know they can be webcam specific, I am willing to buy a new webcam if it means better results). I want to write a desktop application that will take video from a webcam and store it in MPEG4 formats (DivX, Xvid, etc...). I would also like to access bitmap stills from the device so I can do image comparison between frames. I have tried various libraries, and none have really been a great fit (some have performance issues (very inconsistent framerates), some have image quality limitations, some just crash out for seemingly no reason. I want to get high quality video (as high as I can get) and a decent framerate. My webcam is more than up to the job and I was hoping that there would be a nice Managed .Net library around that would help my cause. Are webcam APIs all just incredibly bad?

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• Measuring the time to create and destroy a simple object

  - by portoalet

  From Effective Java 2nd Edition Item 7: Avoid Finalizers "Oh, and one more thing: there is a severe performance penalty for using finalizers. On my machine, the time to create and destroy a simple object is about 5.6 ns. Adding a finalizer increases the time to 2,400 ns. In other words, it is about 430 times slower to create and destroy objects with finalizers." How can one measure the time to create and destroy an object? Do you just do: long start = System.nanoTime(); SimpleObject simpleObj = new SimpleObject(); simpleObj.finalize(); long end = System.nanoTime(); long time = end - start;

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• (NOT) NULL for NVARCHAR columns

  - by Anders Abel

  Allowing NULL values on a column is normally done to allow the absense of a value to be represented. When using NVARCHAR there is aldready a possibility to have an empty string, without setting the column to NULL. In most cases I cannot see a semantical difference between an NVARCHAR with an empty string and a NULL value for such a column. Setting the column as NOT NULL saves me from having to deal with the possibility of NULL values in the code and it feels better to not have to different representations of "no value" (NULL or an empty string). Will I run into any other problems by setting my NVARCHAR columns to NOT NULL. Performance? Storage size? Anything I've overlooked on the usage of the values in the client code?

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• Detect numbers and process them ?

  - by Madhup

  Hi, I am trying to detect the numbers written on a grid and then process them using the iPhone camera. What i have found till yet are some good examples like: http://blog.damiles.com/?p=93 http://cmgresearch.blogspot.com/2010/01/augmented-reality-on-iphone-how-to_01.html Although I am able to draw the numbers on the overlay view to a good extent but still not able to detect what these numbers are. What I don't wanna do is to go through the whole AI process: training the system, providing the system whole set of values and then process them, because this is so much troublesome for me as well for the performance of my application. So guys having any idea or work arround for this please help. Thanks, Madhup

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• Is there a library / tool to query MySQL data files (MyISAM / InnoDB) without the server? (the SQLit

  - by MGW

  Oftentimes I want to query my MySQL data directly without a server running or without having access to the server (but having read / write rights to the files). Is there a tool or maybe even a library around to query MySQL data files like it is possible with SQLite? I'm specifically looking for InnoDB and MyISAM support. Performance is not a factor. I don't have any knowledge about MySQL internals, but I presume it should be possible to do and not too hard to get the specific code out? Thank you for any suggestions!

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• iPhone. How to intercept system dialogs?

  - by Sjakelien

  My app offers the user the opportunity to put an event in his native calendar. For that, I refer to an online webcal:// URL. Since the underlying .ics file is quite big (containing quite a few events), it sometimes (also depending on the network performance)takes a while before the "Do you want to subscribe"-dialog sequence kicks in. I would like to give the user some feedback in the mean time, like a spinner, or a changing graphic, for him to know that something is going to happen. Question: how does my app know, that the "Do you want to subscribe"-dialog has been shown, and that the user has chosen either a Cancel of OK button in that dialog, so I can stop the spinner?

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• Is both approach same ?

  - by Harikrishna

  I have one datatable which is not bindided and records are coming from the file by parsing it in the datatable dynamically every time. Now there is three columns in the datatable Marks1,Marks2 and FinalMarks. And their types is decimal. Now for making addition of columns Marks1 and Marks2 's records and store it into FinalMarks column,For that what I do is : datatableResult.Columns["FinalMarks"].Expression="Marks1+Marks2"; It's works properly. It can be done in other way also is foreach (DataRow r in datatableResult.Rows) { r["FinalMarks"]=Convert.ToDecimal(r["Marks1"])+Convert.ToDecimal(r["Marks2"]); } Now I don't know that which is the best way to do this means performance wise. Is first approach same as second approach in background means is both approach same or what?

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• CAD/CAM without C++

  - by zaladane

  Hello, Is it possible to do CAD/CAM software without having to use C++? My company developed their software with c/C++ but that was more than 10 years ago. Today,there is a lot of legacy code that switching would force us to get rid of but i was wondering what the actual risks are. We have a lot of mathematical algorithms for toolpath calculations, feature recognition and simulation and 3D Rendering and i was wondering if C# can handles all of that without great performance loss. Is it a utopia to rewrite such algorithms in c# or should that language only deal with UI. We are not talking about game development here (Halo 3 or Call Of Duty) so how much processing does CAD/CAM really need? Can anybody enlighten me on this matter? Most of my colleagues are hardcore C++ programmers and although i program in c++ i love .NET but i am having a hard time selling .NET to them other than basic UI. Does it make sense to consider switching to .NET in such a field, or is it just not a wise idea? Thank you

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• When to use Hibernate?

  - by Ramo

  Hi All, I was asked in an interview this question so I answered with the following: -Better Performance: - Efficient queries. - 1st and 2nd level caching. - Good caching gives better scalability. - Good Database Portability: - Changing the DB is as easy as changing the dialect configuration. - Increased Developer Productivity: - Think only in object terms not in query language terms. But I also feel that systems fall in one of the below categories, and Hibernate may not be suited for all these cases, I'm interested in your thoughts about this, do you agree with me? please let me know when would use HB in the following case and why. Write Only Systems: Read Only Systems: Write Mostly Systems: Read Mostly Systems: Regards Ramo

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• asynchronous calls in asp.net

  - by lockedscope

  in this sample, two threads created; a worker thread created by BeginInvoke and an I/O completion thread created by SendAsync method. but another author in his UnsafeQueueNativeOverlapped example, don't recommend this. i want to use SendAsync or ...Async in an asp.net page and i want to use PageAsyncTask. however, its BeginEventHandler requires AsyncResult to be returned which SendAsync does not return. afaik, event based async pattern is the most recommended way so how could we call SendAsync or any ...Async methods without creating two threads and hurting the performance?

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• Stored Procedure or calculations via IQueryable?

  - by Shawn Mclean

  This is a question that is based on choosing performance over design practices. If I have a method that will be executed many times a second; public static IQueryable<IPerson> InRadius(this IQueryable<IPerson> query, Coordinate center, double radius) { return (from u in query where CallHeavyMathFormula(u, center, radius) select u); } This extension method for IQueryable generates a SQL that does some heavy maths calculation (Cosine, Sine, etc). This would mean the application sends 1-2KB of sql to the server per call. I've heard of placing all application logic, in your application. I also would like to change to a database such as azure or one of those scalable databases in the future. How do I handle something like this? Should I leave it as it is now or write stored procedures? How do applications like twitter or facebook do it?

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• "Single NSMutableArray" vs. "Multiple C-arrays" --Which is more Efficient/Practical?

  - by RexOnRoids

  Situation: I have a DAY structure. The DAY structure has three variables or attributes: a Date (NSString*), a Temperature (float), and a Rainfall (float). Problem: I will be iterating through an array of about 5000 DAY structures and graphing a portion of these onto the screen using OpenGL. Question: As far as drawing performance, which is better? I could simply create an NSMutableArray of DAY structures (NSObjects) and iterate on the array on each draw call -- which I think would be hard on the CPU. Or, I could instead manually manage three different C-Arrays -- One for the Date String (2-Dimensional), One for the temperature (1-Dimensional) and One for the Rainfall (1-Dimensional). I could keep track of the current Day by referencing the current index of the iterated C-Arrays.

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• How to synchronize static method in java.

  - by Summer_More_More_Tea

  Hi there: I come up with this question when implementing singleton pattern in Java. Even though the example listed blow is not my real code, yet very similar to the original one. public class ConnectionFactory{ private static ConnectionFactory instance; public static synchronized ConnectionFactory getInstance(){ if( instance == null ){ instance = new ConnectionFactory(); } return instance; } private ConnectionFactory(){ // private constructor implementation } } Because I'm not quite sure about the behavior of a static synchronized method, I get some suggestion from google -- do not have (or as less as possible) multiple static synchronized methods in the same class. I guess when implementing static synchronized method, a lock belongs to Class object is used so that multiple static synchronized methods may degrade performance of the system. Am I right? or JVM use other mechanism to implement static synchronized method? What's the best practice if I have to implement multiple static synchronized methods in a class? Thank you all! Kind regards!

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• Is there any advantage to having more than 16gb ram on a Windows Dev machine?

  - by Robert Kozak

  Assuming a machine (Dual Quad Core Xeon (2.26GHz) with 24GB RAM) running Windows Server 2008 and Hyper-V. How many VMs can I expect to run at the same time with good performance. Is this overkill? Can you really have too much RAM? Assuming 2GB per VM thats around 16GB for the VMs with 8GB left over for the Main OS and Hyper-V. Sound about right? Edit: Tried to make the question sound less like bragging. Was never my intention. Its a hard question to write.

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• Best method of Zend Framework caching

  - by iamthejeff

  I have a blog built using Zend Framework, which I realize might be a bit overkill for a blog alone, but I am planning on adding other features in the future. Nevertheless, I've noticed pages could be a little speedier. I've done a basic caching method that basically captures everything in index.php (Core frontend and File backend), which works great, but unfortunately it also prevents dynamic page contents from updating (messages like "this was posted 5 minutes ago", etc) until the cache period expires. So my question is what would be the best method of caching to improve performance? I am doing fairly basic queries which are mostly simple selects, not many joins or anything fancy (using Zend_Db_Table), and even on a small database page loads are a little sluggish. Is it worth it to cache queries or should I focus my time elsewhere?

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• Advantages of using WCF to work with Sharepoint Services WSS3.0?

  - by val

  Hi folks, what is your opinion or better off your practical experience using WCF to work with WSS instead of SP web services? I am writing some custom library for our software to store and retrieve files from WSS document libraries using sharepoint web services. I am not entirely happy with the performance of the sp web services - a bit too slow in many cases. Now, microsoft claims a significant improvements in WCF over remoting and I am looking into a good way to use WCF for my file services. Any suggestions or ideas? Maybe a good source of coding practices or blogs? Thanks a lot, Val

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• Play a video with flash (with no controls, pause, etc) and stretch to full width and height of page.

  - by Tim

  Hi, I've managed this so far: [removed url] The plan is to have that video stretch across the whole page (the flash does, the video itself does not). Firstly: well aware of the issues - bad performance, horribly stretched/pixelated video. I know this. However a client wants it so we have to do it, simple as that. Does anyone have any ideas on how this can be achieved? I've been in touch with the creators of the flash video player I'm currently using and they've confirmed it isn't possible with that flash video player. Anyone know of any players where it is possible? Thanks, Tim

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• Large static arrays are slowing down class load, need a better/faster lookup method

  - by Visualize

  I have a class with a couple static arrays: an int[] with 17,720 elements a string[] with 17,720 elements I noticed when I first access this class it takes almost 2 seconds to initialize, which causes a pause in the GUI that's accessing it. Specifically, it's a lookup for Unicode character names. The first array is an index into the second array. static readonly int[] NAME_INDEX = { 0x0000, 0x0001, 0x0005, 0x002C, 0x003B, ... static readonly string[] NAMES = { "Exclamation Mark", "Digit Three", "Semicolon", "Question Mark", ... The following code is how the arrays are used (given a character code). [Note: This code isn't a performance problem] int nameIndex = Array.BinarySearch<int>(NAME_INDEX, code); if (nameIndex > 0) { return NAMES[nameIndex]; } I guess I'm looking at other options on how to structure the data so that 1) The class is quickly loaded, and 2) I can quickly get the "name" for a given character code. Should I not be storing all these thousands of elements in static arrays?

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• Rewriting .each() loop as for loop to optimize, how to replicate $(this).attr()

  - by John B

  I running into some performance issues with a jquery script i wrote when running in ie so I'm going through it trying to optimize any way possible. Apparently using for loops is way faster than using the jQuery .each method. This has led me to a question regarding the equivalent of $(this) inside a for loop. I'm simplifying what I'm doing in my loop down to just using an attr() function as it gets across my main underlying question. Im doing this with each(simplified) var existing = $('#existing'); existing.each(function(){ console.log($(this).attr('id')); }); And I've tried rewriting it as a for loop as such: var existing = $('#existing'); for(var i = 0;i < existing.length;i++) { console.log(existing[i].attr('id')); } Its throwing an error saying: Uncaught TypeError: Object #<HTMLDivElement> has no method 'attr' Thanks.

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• Generate a commutative hash based on three sets of numbers?

  - by DarkAmgine

  I need to generate a commutative hash based on three sets of "score" structs. Each score has a "start", an "end" and a "number". Both start and end are usually huge numbers (8-9 digits) but number is just from 1 to 4. I need them to be commutative so the order does not matter. I'm using XOR at the moment but it seems to be giving bad results. Since I'm working with large large datasets, I'd prefer a performance-friendly solution. Any suggestions? Thanks =] public static int getCustomHash(cnvRegion c1, cnvRegion c2, cnvRegion c3) { int part1 = (c1.startLocation * c2.startLocation * c3.startLocation); int part2 = (c1.endLocation * c2.endLocation * c3.endLocation); int part3 = (c1.copyNumber + c2.copyNumber + c3.copyNumber)*23735160; return part1 ^ part2 ^ part3; }

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• Can I tell Borland C++ Builder to copy a file somewhere else after it is built?

  - by MrVimes

  I have two computers. One is intended to be left 'free' for high-performance activities (such as playing games) The other is my 'all purpose' computer where I install all the apps I use for creating things, and so on. On the second computer I use Codegear C++ Builder to work on an app that I use on the first computer. If I have BCB compile to comp 1 it is hopeless. It becomes unresponsive. It compiles locally very quickly. So what I do is compile locally and then copy the exe to the other machine. Well, I'm all for streamlining processes, so I want a way to compile on PC2 and use on PC1 without any intermediate steps. So is it possible to have BCB do the compiling on PC2 and create a local exe file, then copy the file to PC 1?

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• Background upload in PHP

  - by Robijntje007

  I am working with a form that allows me to upload files via a local folder and FTP. So I want to move files over ftp (which already works) Because of performance reasons I chose this process to run in the background so I use nfcftpput (linux) In CLI the following command works perfectly: ncftpput-b-u name -p password -P 1980 127.0.0.1 /upload/ /home/Downloads/upload.zip (Knowing that the b-parameter triggers background process) But if I run it via PHP it does not work (without the-b parameter it does) PHP code: $cmd = "ncftpput -b -u name -p password -P 1980 127.0.0.1 /upload/ /home/Downloads/upload.zip"; $return = exec($cmd);

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