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• How to estimate the thread context switching overhead?

  - by Ignas Limanauskas

  I am trying to improve the performance of the threaded application with real-time deadlines. It is running on Windows Mobile and written in C / C++. I have a suspicion that high frequency of thread switching might be causing tangible overhead, but can neither prove it or disprove it. As everybody knows, lack of proof is not a proof of opposite :). Thus my question is twofold: If exists at all, where can I find any actual measurements of the cost of switching thread context? Without spending time writing a test application, what are the ways to estimate the thread switching overhead in the existing application? Does anyone know a way to find out the number of context switches (on / off) for a given thread?

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• Can I use UIPerformance grails plugin and host my static resources in another domain?

  - by fabien7474

  The UIPerfomance plugin is an easy way to speed up your web pages by applying some of the best practices rules from Yahoo performance team (like minifying, setting a far-future expires header, versioned images...) Unfortunately I didn't find a way to store the static resources in a location outside of the webapplication which has his own advantages ( smaller WAR sizes, better optimize cookieless server, static resources served faster by a highly optimized native httpd, no need to redeploy WAR when updating static resources..). So my question is: is it possible to use this great plugin with static resoures stored outside the web application? And if yes, how?

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• Multiple Broadcast Messages with Less Data or Less Broadcast Messages with More Data?

  - by niko

  Hi, I am developing an application which is communicating with the server. Tha application can perform log-in and get different parameters from server. The application consists of a RESTful client (custom class for making requests), Communication Service (the service which runs in the background) and the main activity. For now I created multiple broadcast messages and multiple broadcast receivers in the main activity so when the application performs login operation a receiver (loginBroadcastReceiver) in the main activity receives a message and when another parameter is received from the server different message is broadcasted and another receiver handles the message. This way however the application performance is poor but I am not sure whether it is due to multiple broadcast receivers. Does anyone know what is the best way to exchange data between service and main activity - is it better to create a single broadcast receiver and retrieve all parameters from message or is it better to initialize multiple broadcast receivers for multiple parameters? I would appreciate if you could provide any useful resource about the topic because I'm writing the thesis and it would be good if the solution could be explained.

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• An Efficient data structure for Sorted List

  - by holydiver

  I want to save my objects according to a key in the attributes of my object in a sorted fashion. Later on I'll access these objects sequentially from max key to min key. I'll do some search tasks as well. I consider to use either AVL tree or RB Tree. As far as i know they are nearly equivalent in theory(Both have O(logn)). But in practice which one might be better in performance in my situation. And is there a better alternative than those, considering that I'll mostly do insert and sequentially access to the ds.

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• Is Win32_PerfFormattedData_PerfDisk_PhysicalDisk missing from WMI in Vista?

  - by Martin

  From what I understand, the following script should work in Windows XP and higher, but it doesn't work for me in Vista Business 32-bit Service Pack 2. Thus far I have been very unsuccessful googling for information about this performance class. strComputer = "." Set objWMIService = GetObject("winmgmts:\\" & strComputer & "\root\cimv2") Set colApps = objWMIService.ExecQuery("Select * from Win32_PerfFormattedData_PerfDisk_PhysicalDisk") For Each objApp in colApps Wscript.Echo objApp.Caption Next Does this WMI class simply not exist in Vista? If it is just me, is there a way to fix WMI? I have already tried running winmgmt /resetrepository and winmgmt /resyncperf and neither helps.

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• Can games be considered real-time systems?

  - by harry

  I've been reading up on real-time systems and how they work etc. I was looking at the wikipedia article as well that said a game of Chess with a timer per move can be considered a real-time system because the program MUST compute a move in that time. What about other games? As we know, games generally try and run at 25+ FPS, could it be considered a soft real-time system since if it falls under 25 (I'm using 25 as a pre-defined threshold btw) it's not the end of the world, just a hit to the performance that we wanted? Also - games have events they must handle as well. The user uses the keyboard/mouse and the system must answer those events accordingly within (again) a pre-defined time, before the game is considered to have "failed". Oh, and I'm talking single-player for now to keep things simple. It sounds like games fit the soft real-time system criteria, but I'd like to know if I'm missing anything... thanks.

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• Setting up a web developer lab for learning purposes

  - by Saleh Al-Abbas

  I'm not a developer by profession. Therefore, I'm not exposed to real world technical problems that face professional developers. I read/heard about web farms, integration between different systems, load balancing ... etc. Therefore, I was wondering if there are ways for the individual developer to create an environment that simulates real world situations with minimal number of machines like: web farms & caching simulating many users accessing your website (Pressure tests?) Performance load balancing anything you think I should consider. By the way, I have a server machine and 1 PC. and I don't mind investing in tools and software. PS. I'm using Microsoft technologies for development but I hope this is not a limiting factor. Thanks

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• What is design principle behind Servlets being Singleton

  - by Sandeep Jindal

  A servlet container "generally" create one instance of a servlet and different threads of the same instance to serve multiple requests. (I know this can be changed using deprecated SingleThreadModel and other features, but this is the usual way). I thought, the simple reason behind this is performance gain, as creating threads is better than creating instances. But it seems this is not the reason. On the other hand, creating instances have little advantage that developers never have to worry about thread safety. I am trying to understand the reason for this decision over the trade-off of thread-safety.

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• Extraction Event

  - by Anicho

  So I have the following code: public override void Extract(object sender, ExtractionEventArgs e) { if (e.Response.HtmlDocument != null) { var myParam = e.Request.QueryStringParameters.Where(parameter => parameter.Name == QueryName).Select(parameter => parameter.Value).Distinct(); myParam. // add the extracted value to the web performance test context e.WebTest.Context.Add(this.ContextParameterName, myParam.ToString()); e.Success = true; return; } // If the extraction fails, set the error text that the user sees e.Success = false; e.Message = String.Format(CultureInfo.CurrentCulture, "Not Found: {0}", QueryName); } It's returning: System.Linq.Enumerable+<DistinctItem>d_81`1[system.string] I am expecting something along the lines of: 0152-1231-1231-123d My question is how do I extract the querystring's actual value from extractioneventargs. They say it's possible, but I have no idea.

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• What Are Basic Tools For A New Project?

  - by Morgan Cheng

  For a long time, I thought that to start a new project we only need 3 basic tools. 1) A Build System (e.g. Maven & CruiseControl) 2) A Version Control System (e.g. CVS & SVN & GIT) 3) A Bug Tracking System (e.g. Bugzilla) Yesterday, a senior guy told me that we need at least one thing more. That is KPI(Key Performance Index). Without KPI, it is impossible to measure whether the project is progressing well or not. KPI is kind of SOFT tool compared to Maven/SVN/Bugzilla. I believe since I missed SOFT tools, there must be some other kind of tools I missed. So, anybody get some ideas what other basic tools necessary for a new project?

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• How to mark empty in a single element in a float array

  - by Vineeth Mohan

  I have a large float (primitive) array and not every element in the array is filled. How can i mark a particular element as EMPTY. I understand this can be achieved by some special symbols but still i would like to know the standard way. Even if i am using some special symbol , how will i handle a situation where the actual data item is the value of special symbol. In short my question is how to implement the NULL feature in a primitive type array in java. PS - The reason why i am not using Float object is to achieve a high memory and speed performance. Thanks Vineeth

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• Out-Of-Memory while doing Core Data migration

  - by Kamchatka

  Hello, I'm migrating a CoreData model between two versions of an application. I was storing binary data as blobs in the previous version and I want to take them out of the blobs for performance. My issue is that during the migration it seems that Core Data loads everything into memory which leads to Low Memory Warnings and then to my app being killed. Apple documentation suggests the following : http://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/CoreDataVersioning/Articles/vmCustomizingTheProcess.html#//apple_ref/doc/uid/TP40005510-SW9 However, it seems to rely on the fact that the large objects are applied different mapping. In my case, all the objects are basically the same and the same mapping has to be applied to each of them. I don't see in this case how I could apply their technique. How should I handle a migration with very large objects ?

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• How does mysql define DISTINCT()

  - by goran

  AFAIK SQL defines two uses of DISTINCT keywords - SELECT DISTINCT field... and SELECT COUNT(DISTINCT field) ... However in one of web applications that I administer I've noticed performance issues on queries like SELECT DISTINCT(field1), field2, field3 ... DISTINCT() on a single column makes no sense and I am almost sure it is interpreted as SELECT DISTINCT field1, field2, field3 ... but how can I prove this? I've searched mysql site for a reference on this particular syntax but could not find any. Does anyone have a link to definition of DISTINCT() in mysql or knows about other authoritative source on this? Best

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• Reasons to learn MSIL

  - by mannu

  Hi, Learning MSIL is fun and all that. Understanding what is going on "under the hood" can in many ways improve how you write your code performance-wise. However, the IL that is produced by the compiler is quite verbose and does not tell the whole story since JIT will optimize away a lot of the code. I, personally, have had good use of my very basic IL understanding when I've had to make a small fix in an assembly I do not have the source code for. But, I could as well have used Reflector to generate C# code. I would like to know if you've ever had good use of MSIL understanding and/or why you think it is worth learning it (except for the fun in it, of course). I'd also like to know if you think one should not learn it and why.

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• Table with a lot of attributes

  - by Robert

  Hi, I'm planing to build some database project. One of the tables have a lot of attributes. My question is: What is better, to divide the the class into 2 separate tables or put all of them into one table. below is an example create table User { id, name, surname,... show_name, show_photos, ...) or create table User { id, name, surname,... ) create table UserPrivacy {usr_id, show_name, show_photos, ...) The performance i suppose is similar due to i can use index.

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• What is .htaccess RewriteRule best practice?

  - by Pablo

  Is it better to have a single RewriteRule with a bunch of RegEx or multiples Rules with fewer RegEx for the server to query? Will there be any performance differences? Heres is an example a single rule with almost all RegEx groups as optional: RewriteRule ^gallery/?([\w]+)?/?([\w]+)?/?([\d]+)?/?([\w]+)/?$ /gallery.php?$1=$2&start=$3&by=$4 [NC] Here are some of the rules lists that would replace the one above: RewriteRule ^gallery/category/([\w]+)/$ /gallery.php?category=$1& [NC] RewriteRule ^gallery/category/([\w]+)/([\d]+)/$ /gallery.php?category=$1&start=$2 [NC] RewriteRule ^gallery/category/([\w]+)/([\d]+)/([\w]+)/$ /gallery.php?category=$1&start=$2&by=$3 [NC] ... RewriteRule ^gallery/tag/([\w]+)/$ /gallery.php?category=$1& [NC] RewriteRule ^gallery/tag/([\w]+)/([\d]+)/$ /gallery.php?category=$1&start=$2 [NC] RewriteRule ^gallery/tag/([\w]+)/([\d]+)/([\w]+)/$ /gallery.php?category=$1&start=$2&by=$3 [NC] ... I'll be glad to hear your options or personal experiences.

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• WCF Service Memory Leaks

  - by Mubashar Ahmad

  Dear Devs I have a very small wcf service hosted in a console app. [ServiceContract] public interface IService1 { [OperationContract] void DoService(); } [ServiceBehavior(InstanceContextMode=InstanceContextMode.PerCall)] public class Service1 : IService1 { public void DoService() { } } and its being called as using (ServiceReference1.Service1Client client = new ServiceReference1.Service1Client()) { client.DoService(new DoServiceRequest()); client.Close(); } Please remember that service is published on basicHttpBindings. Problem Now when i performed above client code in a loop of 1000 i found big difference between "All Heap bytes" and "Private Bytes" performance counters (i used .net memory profiler). After investigation i found some of the objects are not properly disposed following are the list of those objects (1000 undisposed instance were found -- equals to the client calls) (namespace for all of them is System.ServiceModel.Channels) HttpOutput.ListenerResponseHttpOutput.ListenerResponseOutputStream BodyWriterMessage BufferedMessage HttpRequestContext.ListenerHttpContext.ListenerContextHttpInput.ListenerContextInputStream HttpRequestContext.ListenerHttpContext Questions Why do we have lot of undisposed objects and how to control them. Please Help

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• Database indexes - what should they be

  - by WebweaverD

  Most of my database tables have a clear unique index through which lookups are done 90% of the time but I am a bit unsure on this one - I have a table which keeps track of user rating totals for items in my database, I now want to add another table, to track individual ratings with an ip address column to make sure no one can rate something twice. Since I can see this becoming a big, high use table it is important to optimize it correctly. (MYSQL table) This table will have the following fields: rating_id(always - unique), item_id (always - not unique), user_id (optional - not unique), ip_address (always - not unique), rating_value(always - not unique), has_review(bool) Now I envisions 90% the queries going something like this: When a user rates something - select where item_id = x and ip_address = y, (if rows = 0) insert rating When in user account pages - select where ip_address = x or username = y Now none of the fields searched on are unique, can I still use them as indexes (for example item _id and ip_address), can I have two indexes and will this still improve performance over a non indexed table?

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• pros and cons of TryCatch versus TryParse

  - by Vijesh

  What are the pros and cons of using either of the following approaches to pulling out a double from an object? Beyond just personal preferences, issues I'm looking for feedback on include ease of debugging, performance, maintainability etc. public static double GetDouble(object input, double defaultVal) { try { return Convert.ToDouble(input); } catch { return defaultVal; } } public static double GetDouble(object input, double defaultVal) { double returnVal; if (double.TryParse(input.ToString(), out returnVal)) { return returnVal; } else { return defaultVal; } }

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• What is the best way for communication between cluster nodes

  - by Tom

  I have an application written in a combination of ASP/VB6/VBScript and ASP.NET/C# that consists of a website part, SOAP-like webservice part and a queue processing part processing incoming files in a hotfolder. We are used to running under load balancers (Microsoft or other make). Often we need to communicate between the different load balanced servers. Currently we do this through the SQL Server database that is common for all nodes, however, this comes with a performance penalty as each message requires a transaction and continual polling from the other nodes. What would be better ways to achieve this? Tom, Appelby

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• ZendFramework integration with other frameworks

  - by St.Woland

  I want to make this question a guide for those interested in ZendFramework integration with other libraries/frameworks. Searching over StackOverflow doesn't give a broad view on the subject. The question is: which libraries/frameworks do you use in your current ZF-based project? what are the best practices for ZF-based project architecture? I don't mean any components that are already a part of ZF. Please give a description of aditional frameworks you have integrated (like RuckUsing, Smarty, or Doctrine). It also applies to any GUI frameworks (perhaps you use a CSS framework), as well as JS frameworks (not just jQuery or prototype, but rather some advanced structures). The main requirement: it has to be a ZendFramework project. Additional bonus will be given to answers that describe performance optimization.

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• What are the pros and cons to keeping SQL in Stored Procs versus Code

  - by Guy

  What are the advantages/disadvantages of keeping SQL in your C# source code or in Stored Procs? I've been discussing this with a friend on an open source project that we're working on (C# ASP.NET Forum). At the moment, most of the database access is done by building the SQL inline in C# and calling to the SQL Server DB. So I'm trying to establish which, for this particular project, would be best. So far I have: Advantages for in Code: Easier to maintain - don't need to run a SQL script to update queries Easier to port to another DB - no procs to port Advantages for Stored Procs: Performance Security

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• Algorithms to find longest common prefix in a sliding window.

  - by nn

  Hi, I have written a Lempel Ziv compressor and decompressor. I am seeking to improve the time to search the dictionary for a phrase. I have considered K-M-P and Boyer-Moore, but I think an algorithm that adapts to changes in the dictionary would be faster. I've been reading that binary search trees (AVL or with splays) improve the performance of compression time considerably. What I fail to understand is how to bootstrap the binary search tree and insert/remove data. I'm not actually quite sure the significance of each node in the binary search. I am searching for phrases so will each character be considered a node? Also how and what is inserted/removed from the search tree as new data enters the dictionary and old data is removed? The binary search tree sounds like a good payoff since it can adapt to the dictionary, but I'm just not quite sure of how it's used.

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• MySQL - are FK's useful / viable in a web app?

  - by yoda

  Hi all, I've encountered this discussion related to FK's and web applications. Basically some people say that FK's in web applications doesn't represent a real improvement and can even make the application slower in some cases. What do you guys think, what's your experience? -- A quote from Heikki Tuuri, creator of InnoDB engine, founder and CEO of Innobase: InnoDB checks foreign keys as soon as a row is updated, no batching is performed or checks delayed till transaction commit Foreign keys are often serious performance overhead, but help maintain data consistency Foreign Keys increase amount of row level locking done and can make it spread to a lot of tables besides the ones directly updated

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• Function Object in Java .

  - by Tony

  I wanna implement a javascript like method in java , is this possible ? Say , I have a Person class : public class Person { private String name ; private int age ; // constructor ,accessors are omitted } And a list with Person objects: Person p1 = new Person("Jenny",20); Person p2 = new Person("Kate",22); List<Person> pList = Arrays.asList(new Person[] {p1,p2}); I wanna implement a method like this: modList(pList,new Operation (Person p) { incrementAge(Person p) { p.setAge(p.getAge() + 1)}; }); modList receives two params , one is a list , the other is the "Function object", it loops the list ,and apply this function to every element in the list. In functional programming language,this is easy , I don't know how java do this? Maybe could be done through dynamic proxy, does that have a performance trade off?

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