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• Efficiency of while(true) ServerSocket Listen

  - by Submerged

  I am wondering if a typical while(true) ServerSocket listen loop takes an entire core to wait and accept a client connection (Even when implementing runnable and using Thread .start()) I am implementing a type of distributed computing cluster and each computer needs every core it has for computation. A Master node needs to communicate with these computers (invoking static methods that modify the algorithm's functioning). The reason I need to use sockets is due to the cross platform / cross language capabilities. In some cases, PHP will be invoking these java static methods. I used a java profiler (YourKit) and I can see my running ServerSocket listen thread and it never sleeps and it's always running. Is there a better approach to do what I want? Or, will the performance hit be negligible? Please, feel free to offer any suggestion if you can think of a better way (I've tried RMI, but it isn't supported cross-language. Thanks everyone

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• How do I generate different yyparse functions from lex/yacc for use in the same program?

  - by th

  Hi, I want to generate two separate parsing functions from lex/yacc. Normally yacc gives you a function yyparse() that you can call when you need to do some parsing, but I need to have several different yyparses each associated with different lexers and grammars. The man page seems to suggest the -p (prefix) flag, but this didn't work for me. I got errors from gcc that indicated that yylval was not properly being relabeled (i.e. it claims that several different tokens are not defined). Does anyone know the general rpocedure for generating these separate functions? thanks

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• Bug in Mathematica's Integrate with PrincipalValue->True

  - by Janus

  It seems that Mathematica's handling of principal value integrals fails on some corner cases. Consider these two expressions (which should give the same result): Integrate[UnitBox[x]/(x0 - x), {x, -Infinity, Infinity}, PrincipalValue -> True, Assumptions -> {x0 > 0}] /. x0 -> 1 // Simplify Integrate[UnitBox[x]/(x0 - x) /. x0 -> 1, {x, -Infinity, Infinity}, PrincipalValue -> True] In Mathematica 7.0.0 I get I Pi+Log[3] Log[3] Has this been fixed in later versions? Does anybody have an idea for a (more or less) general workaround?

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• basic SQL atomicity "UPDATE ... SET .. WHERE ..."

  - by elgcom

  I have a rather basic and general question about atomicity of "UPDATE ... SET .. WHERE ..." statement. having a table (without extra constraint), +----------+ | id | name| +----------+ | 1 | a | +----+-----+ now, I would execute following 4 statements "at the same time" (concurrently). UPDATE table SET name='b1' WHERE name='a' UPDATE table SET name='b2' WHERE name='a' UPDATE table SET name='b3' WHERE name='a' UPDATE table SET name='b4' WHERE name='a' is there only one UPDATE statement would be executed with table update? or, is it possible that more than one UPDATE statements can really update the table? should I need extra transaction or lock to let only one UPDATE write values into table? thanks

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• How do you sort files numerically?

  - by Zachary Young

  Hello all, First off, I'm posting this because when I was looking for a solution to the problem below, I could not find one on stackoverflow. So, I'm hoping to add a little bit to the knowledge base here. I need to process some files in a directory and need the files to be sorted numerically. I found some examples on sorting--specifically with using the lamba pattern--at wiki.python.org, and I put this together: #!env/python import re tiffFiles = """ayurveda_1.tif ayurveda_11.tif ayurveda_13.tif ayurveda_2.tif ayurveda_20.tif ayurveda_22.tif""".split('\n') numPattern = re.compile('_(\d{1,2})\.', re.IGNORECASE) tiffFiles.sort(cmp, key=lambda tFile: int(numPattern.search(tFile).group(1))) print tiffFiles I'm still rather new to Python and would like to ask the community if there are any improvements that can be made to this: shortening the code up (removing lambda), performance, style/readability? Thank you, Zachary

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• Why No NSAttributedString on the iPhone?

  - by Jasarien

  Hey guys, Does anyone know what made Apple leave out NSAttributedString when turning AppKit into UIKit? The reason I ask is that I would really like to use it in my iPhone app, and there appears to be no replacement or alternative than doing it myself... It is possible to have mixed font attributes on a string - it's just a hell of a lot of work to to achieve something similar that was possible with a few lines of code with NSAttributedString. Also, doing all this extra drawing code myself makes my table view cells really heavy, and really hurts performance. Anyone got any ideas? Any genius's working on an opensource alternative to NSAttributedString?

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• Does the .NET CLR Really Optimize for the Current Processor

  - by dewald

  When I read about the performance of JITted languages like C# or Java, authors usually say that they should/could theoretically outperform many native-compiled applications. The theory being that native applications are usually just compiled for a processor family (like x86), so the compiler cannot make certain optimizations as they may not truly be optimizations on all processors. On the other hand, the CLR can make processor-specific optimizations during the JIT process. Does anyone know if Microsoft's (or Mono's) CLR actually performs processor-specific optimizations during the JIT process? If so, what kind of optimizations?

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• Which can handle a huge surge of queries: SQL Server 2008 Fulltext or Lucene

  - by Luke101

  I am creating a widget that will be installed on several websites and blogs. The widget will analyse the remote webpage title and content, then it will return relevent articles/links on my website. The amount of traffic we expect will be very huge roughly 500K queries a day and up from there. I need the queries to be returned very quickly, so I need the candidate to be high performance, similar to google adsense. The remote title can be from 5 to 50 words and the description we will use no more then 3000 words. Which of these two do you think can handle the load.

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• Should I unit test my JavaScript?

  - by Joseph Silvashy

  I'm curious to if it would be valuable, I'd like to start using QUnit, but I really don't know where to get started. Actually I'm not going to lie, I'm new to testing in general, not just with JS. I'm hoping to get some tips to how I would start using unit testing with an app that already has a large amount of JavaScript (ok so about 500 lines, not huge, be enough to make me wonder if I have regression that goes unnoticed). How would you recommend getting started and Where would I write my tests? (for example its rails app, where is a logical place to have my JS tests, it would be cool if they could go in the /test directory but it's outside the public directory and thus not possible... err is it?)

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• How can I efficiently select several unique random numbers from 1 to 50, excluding x?

  - by Cocorico

  I have 2 numbers which are between 0 and 49. Let's call them x and y. Now I want to get a couple of other numbers which are not x or y, but are also between 0 and 49 (I am using Objective C but this is more of a general theory question I think?). Method I thought of is: int a; int b; int c; do { a = arc4random() % 49; } while ((a == x) || (a == y)); do { b = arc4random() % 49; } while ((b == x) || (b == y) || (b == a)); do { c = arc4random() % 49; } while ((c == x) || (c == y) || (c == a) || (c == b)); But it seem kind of bad to me, I don't know, I am just trying to learn to be a better programmer, what would be the most elegant way to do this for best practices?

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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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• Using * in SELECT Query

  - by libregeek

  I am currently porting an application written in MySQL3 and PHP4 to MySQL5 and PHP5. On analysis I found several SQL queries which uses "select * from tablename" even if only one column(field) is processed in PHP. The table has almost 60 columns and it has a primary key. In most cases, the only column used is id which is the primary key. Will there be any performance boost if I use queries in which the column names are explicitly mentioned instead of * ? (In this application there is only one method which we need all the columns and all other methods return only a subset of the columns)

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• Is frameworks really necessary for this problem?

  - by The Elite Gentleman

  Hi Guys I'm creating an online music store application (in Java) for signed and unsigned artist for my client. I'm currently using Struts 1.3.10 (I was recommended Spring but Spring setup is sort of similar to Struts) for my Web application. My Database is currently a MySQL 5 (or higher) and I'm using a DAO pattern to talk to it. There are limitations to using Struts and DAO's (e.g. Multiple File upload in Struts is not implemented the same way as multiple String parameters, and for DAO's, there lacks a Publish-Subscribe feature). Is what I'm doing the best way forward or should I go straight Hibernate (or similar) and move out of Struts? What are the performance implications or technical issues that you've experienced with the same setup I have? The client doesn't care how I do it as long as it is done.

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• Logging from multiple apps/processes to a single log file

  - by Andrew

  Our app servers (weblogic) all use log4j to log to the same file on a network share. On top of this we have all web apps in a managed server logging errors to a common error.log. I can't imagine this is a good idea but wanted to hear from some pros. I know that each web app has its own classloader, so any thread synchronization only occurs within the app. So what happens when multiple processes start converging on a single log file? Can we expect interspersed log statements? Performance problems? What about multiple web apps logging to a common log file? The environment is Solaris.

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• "Socket operation on non-socket" error due to strange syntax

  - by Robert S. Barnes

  I ran across the error Socket operation on non-socket in some of my networking code when calling connect and spent a lot of time trying to figure out what was causing it. I finally figured out that the following line of code was causing the problem: if ((sockfd = socket( ai->ai_family, ai->ai_socktype, ai->ai_protocol) < 0)) { See the problem? Here's what the line should look like: if ((sockfd = socket( ai->ai_family, ai->ai_socktype, ai->ai_protocol)) < 0) { What I don't understand is why the first, incorrect line doesn't produce a warning. To put it another way, shouldn't the general form: if ( foo = bar() < baz ) do_something(); look odd to the compiler, especially running with g++ -Wall -Wextra? If not, shouldn't it at least show up as "bad style" to cppcheck, which I'm also running as part of my compile?

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• What is the motivation behind "Use Extension Methods Sparingly?"

  - by Robert Harvey

  I find them a very natural way to extend existing classes, especially when you just need to "spot-weld" some functionality onto an existing class. Microsoft says, "In general, we recommend that you implement extension methods sparingly and only when you have to." And yet extension methods form the foundation of Linq; in fact, Linq was the reason extension methods were created. Are there specific design criteria where using extension methods are perferred over inheritance or composition? Under what criteria are they discouraged?

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• how can I design a good architechture for a Transaction Processing System?

  - by ghedas

  I have a project that must design an architecture for it. This project is a something like a Transaction Processing system and I need to know something like this: when and where I must use synchronous and asynchronous relations between its components? If always I use synchronous relations, the amount of messages maybe become exceeded and makes problem for TP system, and on the other hand synchronous relations make lots of delay, I think a mixture of them is required! If other parameters required to considering please help me! the most nonfunctional requirements of this project are performance and availability of it. I need useful materials and suggestions for it.

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• How Manage Big Linq DataContext ?

  - by Rev

  Hi The major problem in .net programs is "How manage memory for best performance". so Microsoft use garbage collector in .net and with that, we don't need to do something for managing memory(or better say we can use GC easily) But when you develop big project(business app), you make too many tables and database for your own project. so if you use Linq-to-sql, we must build DataContext include hundred or more tables. That make problem for program when you create an object from datacontext, that object give big amount of memory. also we cant divide datacontext to datacontexts(cuz relation between tables) so "How manage datacontext and memory"?

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• jQuery Resizable() UI Problem

  - by OneNerd

  In general, resizable() works fine. Here is where I am getting into an issue. I have a div that contains some resizable items that work fine (resizable() applied to them at some point). user can save items for later view (the innerHTML of the div gets saved into a JavaScript array, then div gets cleared so they can do something else) When items get placed back onto div (from array) -- I do a $('#divname').append(arrayname[i]); -- items are no longer resizable (although visually they have the resizable classes/handle on them) Here is what I have tried so far (none of which have worked): After append() line, I re-initialize the resizable -- $('#items').resizable(); After append() line, remove then re-add resizable -- $('#items').resizable('destroy').resizable(); Any help is appreciated - thanks.

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• Installing a python wrapper for a c++ library

  - by Eugene Kogan

  Hi all, I am trying to install the python wrapper for the ANN (approx near neighbors) c++ library: link is http://www.scipy.org/scipy/scikits/wiki/AnnWrapper . I am on Windows 7 32-bit. Unfortunately the documentation is a bit terse and I am a newbie to programming in general, so I cannot decipher the instructions found within. I have not built a C++ library before and am not even sure how to get that far. Can anyone please guide? Thanks! gene

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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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• Reinstall TeamCity when Tomcat becomes corrupt

  - by dodegaard

  I've got a TeamCity 4 installation where tomcat has bit the dust with the following error "The APR Based Apache Tomcat Native library which allows for optimal performance in production environments was not found in java.library path". It appears this started happening once the JDK was installed on the server to allow for a compile. The JDK has been removed and the JRE reinstalled but still no go. My question is should I reinstall TeamCity completely or is there a way to simply reinstall tomcat so I don't hose the configuration? Your help is greatly appreciated.

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• Need help converting apache .htaccess code to lighttpd url_rewrite code

  - by miCRoSCoPiC_eaRthLinG

  Hi All, I have this custom written CMS built on XAMPP. I'm trying to test the same on lighttpd to benchmark the so-called performance gains... but am stuck at the rewrite rules. I use the default rewrite rules of WordPress in my .htaccess which hands all url parsing over to my script as long as there aren't any files or directories same as the URL structure. Here's the code: RewriteBase /somedir/ # Let the Script handle all pretty URLs RewriteCond %{SCRIPT_FILENAME} !-d RewriteCond %{SCRIPT_FILENAME} !-f RewriteRule .* index.php [L] Can anyone please help me translate the same to the lighttpd format? I could only (partially) figure out the last line myself going through the lighty docs ... i.e. url.rewrite-once = ( ".*" => "index.php" ) But that of course won't suffice... All my CMS is doing is giving me 404's. Thanks, miCRoSCoPiC^eaRthLinG

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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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• Using Large Lists

  - by cam

  In an Outlook AddIn I'm working on, I use a list to grab all the messages in the current folder, then process them, then save them. First, I create a list of all messages, then I create another list from the list of messages, then finally I create a third list of messages that need to be moved. Essentially, they are all copies of eachother, and I made it this way to organize it. Would it increase performance if I used only one list? I thought lists were just references to the actual item.

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