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• How do you keep all your languages straight?

  - by Chris Blackwell

  I think I'm going a little crazy. Right now, I'm working with the following languages (I was just doing a mental inventory): C++ - our game engine Assembler - low level debugging and a few co-processor specific routines Lua - our game engine scripting language HLSL - for shaders Python - our build system and utility tools Objective C/C++ - game engine platform code for Mac and iPhone C# - A few tools developed in our overseas office ExtendScript - Photoshop exporting tools ActionScript - UI scripting VBScript - some spreadsheet related stuff PHP - some web related stuff SQL - some web and tool related stuff On top of this are the plethora of API's that often have many different ways of doing the same thing: std library, boost, .NET, wxWidgets, Cocoa, Carbon, native script libraries for Python, Lua, etc, OpenGL, Direct3d, GDI, Aqua, augh! I find myself inadvertently conflating languages and api's, not realizing what I'm doing until I get syntax errors. I feel like I can't possibly keep up with it, and I can't possibly be proficient in all of these areas. Especially outside the realm of C++ and Python, I find myself programming more by looking at manuals that from memory. Do you have a similar problem? Ideas for compartmentalizing so you're more efficient? Deciding where you want to stay proficient? Organizational tips? Good ways to remember when you switch from Lua to C++ you need to start using semi-colons again? Rants on how complicated we programmers have made things for ourselves? Any ideas welcome!

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• Incompatibility between x86 and x64 in Installation solution

  - by rodnower

  Hello, I have installation solution that have installer project (not web installer but simple installer) that installs NT services, web service and web sites with help of additional two projects of dlls with my own code that performs my installation step. In user actions of installer project I call installer function of one of those projects, and this project calls to installer of second project: installer - MiddleCaller - InstallationCore. All this developing on Windows 7 and work fine when I compile all in 32 bit. The project must run on Windows 2008. Because of some reasons all must be in x64 bit. For this purpose, in MiddleCaller and InstallationCore I click right button of mouse on project - build - targer x64. For to move installer project to 64 bit in properties of installer (when project is active) I check: Target platform: x64. When I run installation on x86 I get error: The installation package is not supported by this processor type" And this is good, because now I know that my installation compiled in 64 bit, but when I run this on windows 2008 I get: Error 1001. Exception occured while initializing the instance: System.BadImageFormatException: could not load file or Assembly 'MiddleCaller, v...' or one of its dependencies. An attempt was made to load a program with an incorrect format. Any one has some idea what I need to do for run fine the installation on x64? May be I still not moved the installer project to x64 bit, if yes, where I do this? Thank you for ahead.

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• Start or ensure that Delayed Job runs when an application/server restarts.

  - by btelles

  Hi there, We have to use delayed_job (or some other background-job processor) to run jobs in the background, but we're not allowed to change the boot scripts/boot-levels on the server. This means that the daemon is not guaranteed to remain available if the provider restarts the server (since the daemon would have been started by a capistrano recipe that is only run once per deployment). Currently, the best way I can think of to ensure the delayed_job daemon is always running, is to add an initializer to our Rails application that checks if the daemon is running. If it's not running, then the initializer starts the daemon, otherwise, it just leaves it be. The question, therefore, is how do we detect that the Delayed_Job daemon is running from inside a script? (We should be able to start up a daemon fairly easily, bit I don't know how to detect if one is already active). Anyone have any ideas? Regards, Bernie Based on the answer below, this is what I came up with. Just put it in config/initializers and you're all set: #config/initializers/delayed_job.rb DELAYED_JOB_PID_PATH = "#{Rails.root}/tmp/pids/delayed_job.pid" def start_delayed_job Thread.new do `ruby script/delayed_job start` end end def process_is_dead? begin pid = File.read(DELAYED_JOB_PID_PATH).strip Process.kill(0, pid.to_i) false rescue true end end if !File.exist?(DELAYED_JOB_PID_PATH) && process_is_dead? start_delayed_job end

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• What's the "best" database for embedded?

  - by mawg

  I'm an embedded guy, not a database guy. I've been asked to redesign an existing system which has bottlenecks in several places. The embedded device is based around an ARM 9 processor running at 220mHz. There should be a database of 50k entries (may increase to 250k) each with 1k of data (max 8 filed). That's approximate - I can try to get more precise figures if necessary. They are currently using SqlLite 2 and planning to move to SqlLite 3. Without starting a flame war - I am a complete d/b newbie just seeking advice - is that the "best" decision? I realize that this might be a "how long is a piece of string?" question, but any pointers woudl be greatly welcomed. I don't mind doing a lot of reading & research, but just hoped that you could get me off to a flying start. Thanks. p.s Again, a total rewrite, might not even stick with embedded Linux, but switch to eCos, don't worry too much about one time conversion between d/b formats. Oh, and accesses should be infrequent, at most one every few seconds. edit: ok, it seems they have 30k entries (may reach 100k or more) of only 5 or 6 fields each, but at least 3 of them can be a search key for a record. They are toying with "having no d/b at all, since the data are so simple", but it seems to me that with multiple keys, we couldn't use fancy stuff like a quicksort() type search (recursive, binary search). Any thoughts on "no d/b", just data-structures? Btw, one key is 800k - not sure how well SqlLite handles that (maybe with "no d/b" I have to hash that 800k to something smaller?)

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• Login Facebook using Web-Harvest

  - by parin

  I tried to login Facebook using Web-Harvest. I used the following xml code to login < ?xml version="1.0" encoding="UTF-8"? < config charset="ISO-8859-1" < file action="write" path="homepage.xml" charset="UTF-8" < html-to-xml < http method="post" url="http://www.facebook.com/login.php" cookie-policy="browser" < http-param name="email"myemail < http-param name="pass"mypassword < /http < /html-to-xml < /file The homepage.xml (output) file contains the xml code for the login page of facebook along with the following lines: < h2 class="main_message" id="standard_error"Cookies Required< /h2< p class="sub_message" id="standard_explanation"Cookies are not enabled on your browser. Please adjust this in your security preferences before continuing.< /p I tried all the allowed values for cookie-policy in the http processor of the xml code but was unsuccessful.

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• what can be causes of http server crash?

  - by mithunmo

  Hello , I am using WAMP server on Windows XP. - Apache 2.2.11 - MySQL 5.1.36 (INNODB engine) - PHP 5.3.0 I observe that my WAMP server crashes in the following scenarios 1) IF I use a Low end PC ( low processor speed and low RAM) 2) After making some changes to httpd.conf file .For eg changing the Allow from IP address . But here it crashes only once and then it starts to work fine. 3) Random crashes CRASH LOG szAppName : httpd.exe szAppVer : 2.2.11.0 szModName : php5ts.dll szModVer : 5.3.0.0 offset : 0000c309 C:\DOCUME~1\blrcom\LOCALS~1\Temp\WERc677.dir00\httpd.exe.mdmp C:\DOCUME~1\blrcom\LOCALS~1\Temp\WERc677.dir00\appcompat.txt My questions 1) Does high CPU utilization/LOW RAM can also cause the HTTP server to crash ? 2) excessive file reading as in every 10 seconds ? 3) unlimited script execution time . I have set the maximum execution time in php script to 0 as my script has to execute for sometimes 2-3 days. Is there any way to avoid this ? 4) Access to Database ? Should we use lock before reading and writing Can these be the reasons for random wamp server crashes ? OR is is some other programming error ? Please guide me . Regards, Mithun

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• Assembly Language bug with space character

  - by Bobby

  Having a bit of difficulty getting my input to print once a white space character is inputted. So far, i have it to display the uppercase/lowercase of the input but once i enter a string it doesnt read whats after the white space character. any suggestions? EDIT: intel x86 processor and im using EMU8086 org 100h include 'emu8086.inc' printn "Enter string to convert" mov dx,20 call get_string printn mov bx,di mov ah,0eh mov al,[ds+bx] cmp al, 41h cmp al, 5Ah jle ToLower1 cmp al, 61h cmp al, 7ah jle ToUpper1 ToLower1: add al, 20h int 10h jmp stop1 ToUpper1: sub al, 20h int 10h stop1: inc bx mov al,[ds+bx] cmp al, 41h cmp al, 5Ah jle ToLower2 cmp al, 61h cmp al, 7ah jle ToUpper2 ToLower2: add al, 20h int 10h jmp stop2 ToUpper2: sub al, 20h int 10h stop2: inc bx mov al,[ds+bx] cmp al, 41h cmp al, 5Ah jle ToLower3 cmp al, 61h cmp al, 7ah jle ToUpper3 ToLower3: add al, 20h int 10h jmp stop3 ToUpper3: sub al, 20h int 10h stop3: inc bx mov al,[ds+bx] cmp al, 41h cmp al, 5Ah jle ToLower4 cmp al, 61h cmp al, 7ah jle ToUpper4 ToLower4: add al, 20h int 10h jmp stop4 ToUpper4: sub al, 20h int 10h stop4: inc bx mov al,[ds+bx] cmp al, 41h cmp al, 5Ah jle ToLower5 cmp al, 61h cmp al, 7ah jle ToUpper5 ToLower5: add al, 20h int 10h jmp stop5 ToUpper5: sub al, 20h int 10h stop5: printn hlt define_get_string define_print_string end

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• Java and tomcat vs ASP.NET and IIS

  - by Mark Cooper

  Until recently I'd considered myself to be a pretty good web programmer (coming up for 10yrs commercial experience on a variety of e-commerce, static and enterprise applications). I'm self taught and have always used the Microsoft product stack (ASP, ASP.NET)... My applications are always functional, relatively bug free, but have never been lightening quick. As a frequent web user I always found this to be the norm... how fast are the websites from the big tech players (eBay, Facebook, Microsoft, IBM, Dell, Telerik etc etc) - in truth none are particularly fast. I always attributed this to "the way things are with web apps"... ...then I cam across a product called Jira from atlasian and this has stopped me in my tracks... This application is fast, and I mean blindingly fast.. too fast to time the switches between pages, fully live content, lots of images and data and cross references etc etc... I run this on an intranet, with a large application DB, and this is running on a very normal server (single processor, SATA HDD, 8GB RAM). Am I missing something?? Are my programming techniques that bad?? I am wondering if this speed gain is down to it being written in Java and running on Tomcat. Does anyone have any benchmarks to compare JSP / ASP or Tomcat / IIS??? Thanks, Mark NOTE: this isn't a blatant plug for Jira. I don't work for them or have any affiliation to them... but I would like to be able to write applications like them :)

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• Nonblocking Tcp server

  - by hoodoos

  It's not a question really, i'm just looking for some guidelines :) I'm currently writing some abstract tcp server which should use as low number of threads as it can. Currently it works this way. I have a thread doing listening and some worker threads. Listener thread is just sits and wait for clients to connect I expect to have a single listener thread per server instance. Worker threads are doing all read/write/processing job on clients socket. So my problem is in building efficient worker process. And I came to some problem I can't really solve yet. Worker code is something like that(code is really simple just to show a place where i have my problem): List<Socket> readSockets = new List<Socket>(); List<Socket> writeSockets = new List<Socket>(); List<Socket> errorSockets = new List<Socket>(); while( true ){ Socket.Select( readSockets, writeSockets, errorSockets, 10 ); foreach( readSocket in readSockets ){ // do reading here } foreach( writeSocket in writeSockets ){ // do writing here } // POINT2 and here's the problem i will describe below } it works all smothly accept for 100% CPU utilization because of while loop being cycling all over again, if I have my clients doing send-receive-disconnect routine it's not that painful, but if I try to keep alive doing send-receive-send-receive all over again it really eats up all CPU. So my first idea was to put a sleep there, I check if all sockets have their data send and then putting Thread.Sleep in POINT2 just for 10ms, but this 10ms later on produces a huge delay of that 10ms when I want to receive next command from client socket.. For example if I don't try to "keep alive" commands are being executed within 10-15ms and with keep alive it becomes worse by atleast 10ms :( Maybe it's just a poor architecture? What can be done so my processor won't get 100% utilization and my server to react on something appear in client socket as soon as possible? Maybe somebody can point a good example of nonblocking server and architecture it should maintain?

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• MySQL Unique hash insertion

  - by Jesse

  So, imagine a mysql table with a few simple columns, an auto increment, and a hash (varchar, UNIQUE). Is it possible to give mysql a query that will add a column, and generate a unique hash without multiple queries? Currently, the only way I can think of to achieve this is with a while, which I worry would become more and more processor intensive the more entries were in the db. Here's some pseudo-php, obviously untested, but gets the general idea across: while(!query("INSERT INTO table (hash) VALUES (".generate_hash().");")){ //found conflict, try again. } In the above example, the hash column would be UNIQUE, and so the query would fail. The problem is, say there's 500,000 entries in the db and I'm working off of a base36 hash generator, with 4 characters. The likelyhood of a conflict would be almost 1 in 3, and I definitely can't be running 160,000 queries. In fact, any more than 5 I would consider unacceptable. So, can I do this with pure SQL? I would need to generate a base62, 6 char string (like: "j8Du7X", chars a-z, A-Z, and 0-9), and either update the last_insert_id with it, or even better, generate it during the insert. I can handle basic CRUD with MySQL, but even JOINs are a little outside of my MySQL comfort zone, so excuse my ignorance if this is cake. Any ideas? I'd prefer to use either pure MySQL or PHP & MySQL, but hell, if another language can get this done cleanly, I'd build a script and AJAX it too. Thanks!

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• C#: WebBrowser.Navigated Only Fires when I MessageBox.Show();

  - by tsilb

  I have a WebBrowser control which is being instantiated dynamically from a background STA thread because the parent thread is a BackgroundWorker and has lots of other things to do. The problem is that the Navigated event never fires, unless I pop a MessageBox.Show() in the method that told it to .Navigate(). I shall explain: ThreadStart ts = new ThreadStart(GetLandingPageContent_ChildThread); Thread t = new Thread(ts); t.SetApartmentState(ApartmentState.STA); t.Name = "Mailbox Processor"; t.Start(); protected void GetLandingPageContent_ChildThread() { WebBrowser wb = new WebBrowser(); wb.Navigated += new WebBrowserNavigatedEventHandler(wb_Navigated); wb.Navigate(_url); MessageBox.Show("W00t"); } protected void wb_Navigated(object sender, WebBrowserNavigatedEventArgs e) { WebBrowser wb = (WebBrowser)sender; // Breakpoint HtmlDocument hDoc = wb.Document; } This works fine; but the messagebox will get in the way since this is an automation app. When I remove the MessageBox.Show(), the WebBrowser.Navigated event never fires. I've tried supplanting this line with a Thread.Sleep(), and by suspending the parent thread. Once I get this out of the way, I intend to Suspend the parent thread while the WebBrowser is doing its job and find some way of passing the resulting HTML back to the parent thread so it can continue with further logic. Why does it do this? How can I fix it? If someone can provide me with a way to fetch the content of a web page, fill out some data, and return the content of the page on the other side of the submit button, all against a webserver that doesn't support POST verbs nor passing data via QueryString, I'll also accept that answer as this whole exercise will have been unneccessary.

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• How to setup matlabpool for multiple processors?

  - by JohnIdol

  I just setup a Extra Large Heavy Computation EC2 instance to throw it at my Genetic Algorithms problem, hoping to speed up things. This instance has 8 Intel Xeon processors (around 2.4Ghz each) and 7 Gigs of RAM. On my machine I have an Intel Core Duo, and matlab is able to work with my two cores just fine by runinng: matlabpool open 2 On the EC2 instance though, matlab only is capable of detecting 1 out of 8 processors, and if I try running: matlabpool open 8 I get an error saying that the ClusterSize is 1 since there's only 1 core on my CPU. True, there is only 1 core on each CPU, but I have 8 CPUs on the given EC2 instance! So the difference from my machine and the ec2 instance is that I have my 2 cores on a single processor locally, while the EC2 instance has 8 distinct processors. My question is, how do I get matlab to work with those 8 processors? I found this paper, but it seems related to setting up matlab with multiple EC2 instances (not related to multiple processors on the same instance, EC2 or not), which is not my problem. Any help appreciated!

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• Matlab crashes on library initialize when called from Java

  - by David Sauter

  Hello everyone. The setup I have is I'm using a Java application to call native C-code with JNI, which in turn starts up the MATLAB runtime and calls functions on it (I know there are other solutions to call MATLAB methods from Java). The problem is that the MATLAB engine crashes at some point during the initialization and I don't know what's causing it exactly. The crash causes my jvm to terminate, I assume it's some kind of memory corruption. The C++ code calling MATLAB functions that is actually crashing is JNIEXPORT void JNICALL some_jni_vodoo_initializeLibrary(JNIEnv* env, jclass thisClass) { try { if (!mclInitializeApplication(NULL, 0)) { THROW_EXCEPTION(env, "Could not initialize the application properly."); return; } if (!<library>Initialize()) { THROW_EXCEPTION(env, "Could not initialize the library."); return; } } ... The function <library>Initialize() crashes here, the Java error log reads Stack Trace: [0] jmi.dll:0x793f4175(0x7934cdca, 1, 0x7937e67c "à;.y`[email protected] in C:\BUILD_ARE..", 0x792d6a32) [1] jvm.dll:0x792df9a5(0xc0000005, 0x79356791, 0x4961b400 "Ð\8y", 0x6d8b29de) [2] jvm.dll:0x792e0431(0x8b515008, 0x70f0e8ce, 0x8b5ffffa, 0xc25d5ec6) ------------------------------------------------------------------------ Fatal Java Exception detected at Fri Apr 30 11:08:08 2010 ------------------------------------------------------------------------ Configuration: MATLAB Version: 7.8.0.347 (R2009a) MATLAB License: unknown Operating System: Microsoft Windows Vista Window System: Version 6.0 (Build 6002: Service Pack 2) Processor ID: x86 Family 6 Model 10 Stepping 5, GenuineIntel Virtual Machine: Java is not enabled Default Encoding: windows-1252 Java is not enabled I really have no idea what could be wrong. Is there not enough memory from the jvm? I guess the problem is somehow related to Java, since calling the JNI functions from a simple test C++ program works fine... Thanks

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• FOR BOUNTY: "QFontEngine(Win) GetTextMetrics failed ()" error on 64-bit Windows

  - by David Murdoch

  I'll add a large bounty to this when Stack Overflow lets me. I'm using wkhtmltopdf to convert HTML web pages to PDFs. This works perfectly on my 32-bit dev server [unfortunately, I can't ship my machine :-p ]. However, when I deploy to the web application's 64-bit server the following errors are displayed: C:\>wkhtmltopdf http://www.google.com google.pdf Loading pages (1/5) QFontEngine::loadEngine: GetTextMetrics failed () ] 10% QFontEngineWin: GetTextMetrics failed () QFontEngineWin: GetTextMetrics failed () QFontEngine::loadEngine: GetTextMetrics failed () QFontEngineWin: GetTextMetrics failed () QFontEngineWin: GetTextMetrics failed () QFontEngineWin: GetTextMetrics failed () QFontEngine::loadEngine: GetTextMetrics failed () ] 36% QFontEngineWin: GetTextMetrics failed () QFontEngineWin: GetTextMetrics failed () // ...etc.... and the PDF is created and saved... just WITHOUT text. All form-fields, images, borders, tables, divs, spans, ps, etc are rendered accurately...just void of any text at all. Server information: Windows edition: Windows Server Standard Service Pack 2 Processor: Intel Xeon E5410 @ 2.33GHz 2.33 GHz Memory: 8.00 GB System type: 64-bit Operating System Can anyone give me a clue as to what is happening and how I can fix this? Also, I wasn't sure what to tag/title this question with...so if you can think of better tags/title comment them or edit the question. :-)

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• Oracle performance problems with large batch of XSL operations

  - by FrustratedWithFormsDesigner

  I have a system that is performing many XSL transformations on XMLType objects. The problem is that the system gradually slows down over time, and sometimes crashes when it runs out of memory. It seems that the slow down (and possibly memory crash) is around the dbms_xslprocessor.processXSL function call, which gradually takes longer and longer to complete. The code looks like this: v_doc dbms_xmldom.DOMDocument; v_transformer dbms_xmldom.DOMDocument; v_XSLprocessor dbms_xslprocessor.Processor; v_stylesheet dbms_xslprocessor.Stylesheet; v_clob clob; ... transformer := PKG_STUFF.getXSL(); v_transformer := dbms_xmldom.newDOMDocument(transformer); v_XSLprocessor := Dbms_Xslprocessor.newProcessor; v_stylesheet := dbms_xslprocessor.newStylesheet(v_transformer, ''); ... for source_data in (select id in source_tbl) loop begin v_doc := PKG_CONVERT.convert(in_id => source_data.id); --start time of operation v_begin_op_time := dbms_utility.get_time; --reset the CLOB v_clob := ' '; --Apply XSL Transform dbms_xslprocessor.processXSL(p => v_XSLprocessor, ss => v_stylesheet, xmldoc => v_Doc, cl => v_clob); v_doc := dbms_xmldom.newDOMDocument(XMLType(v_clob)); --end time v_end_op_time := dbms_utility.get_time; --calculate duration v_time_taken := (((v_end_op_time - v_begin_op_time))); --log the duration PKG_LOG.log_message('Time taken to transform XML: '||v_time_taken); ... ... DBMS_XMLDOM.freeDocument(v_Doc); DBMS_LOB.freetemporary(lob_loc => v_clob); end loop; The time taken to transform the XML is slowly creeping up (I suppose it might also be the call to dbms_xmldom.newDOMDocument, but I had thought that to be fairly straightforward). I have no idea why.... :( (Oracle 10g)

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• saxon java xpath exception :

  - by changed

  Hi I am trying to read XPath queries from a file and run it against a xml data file. I am doing it through Saxon Xpath processor. But i keep getting this error. Code i am using is from sample code provided with the library. Error i am getting is : Exception in thread "main" javax.xml.xpath.XPathExpressionException: Supplied node must be built using the same or a compatible Configuration at net.sf.saxon.xpath.XPathExpressionImpl.evaluate(XPathExpressionImpl.java:283) at net.sf.saxon.xpath.XPathExpressionImpl.evaluate(XPathExpressionImpl.java:375) at edu.xml.XPathExample.go(XPathExample.java:81) at edu.xml.XPathExample.main(XPathExample.java:42) - public void go(String filename) throws Exception { XPathExpression findLine = null; String readLine = null; Object document = new XPathEvaluator().setSource(new StreamSource(new File(dataPath))); System.setProperty("javax.xml.xpath.XPathFactory:" + NamespaceConstant.OBJECT_MODEL_SAXON, "net.sf.saxon.xpath.XPathFactoryImpl"); XPathFactory xpf = XPathFactory.newInstance(NamespaceConstant.OBJECT_MODEL_SAXON); XPath xpe = xpf.newXPath(); if (filename != null) { this.queryPath = filename; } try { fileReader = new BufferedReader(new FileReader(queryPath)); } catch (FileNotFoundException ex) { System.out.println("File not found: " + ex.getMessage()); } xpe.setXPathVariableResolver(this); while (true) { try { readLine = fileReader.readLine(); } catch (IOException ex) { System.out.println("Error while reading file: " + ex.getMessage()); } if (readLine == null) { break; } findLine = xpe.compile(readLine); String resultString = findLine.evaluate(document); System.out.println("<output>"); System.out.println("String Value => " + resultString); System.out.println("</output>"); } }

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• "QFontEngine(Win) GetTextMetrics failed ()" error on 64-bit Windows

  - by David Murdoch

  I'll add 500 of my own rep as a bounty when SO lets me. I'm using wkhtmltopdf to convert HTML web pages to PDFs. This works perfectly on my 32-bit dev server [unfortunately, I can't ship my machine :-p ]. However, when I deploy to the web application's 64-bit server the following errors are displayed: C:\>wkhtmltopdf http://www.google.com google.pdf Loading pages (1/5) QFontEngine::loadEngine: GetTextMetrics failed () ] 10% QFontEngineWin: GetTextMetrics failed () QFontEngineWin: GetTextMetrics failed () QFontEngine::loadEngine: GetTextMetrics failed () QFontEngineWin: GetTextMetrics failed () QFontEngineWin: GetTextMetrics failed () QFontEngineWin: GetTextMetrics failed () QFontEngine::loadEngine: GetTextMetrics failed () ] 36% QFontEngineWin: GetTextMetrics failed () QFontEngineWin: GetTextMetrics failed () // ...etc.... and the PDF is created and saved... just WITHOUT text. All form-fields, images, borders, tables, divs, spans, ps, etc are rendered accurately...just void of any text at all. Server information: Windows edition: Windows Server Standard Service Pack 2 Processor: Intel Xeon E5410 @ 2.33GHz 2.33 GHz Memory: 8.00 GB System type: 64-bit Operating System Can anyone give me a clue as to what is happening and how I can fix this? Also, I wasn't sure what to tag/title this question with...so if you can think of better tags/title comment them or edit the question. :-)

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• "Work stealing" vs. "Work shrugging (tm)"?

  - by John

  Why is it that I can find lots of information on "work stealing" and nothing on a "work shrugging(tm)" as a load-balancing strategy? I am surprised because work-stealing seems to me to have an inherent weakness when implementating efficient fine-grained load-balancing. Vis:- Relying on consumer processors to implement distribution (by actively stealing) begs the question of what these processors do when they find no work? None of the work-stealing references and implementations I have come across so far address this issue satisfactorarily for me. They either:- 1) Manage not to disclose what they do with idle processors! [Cilk] (?anyone know?) 2) Have all idle processors sleep and wake periodically and scatter messages to the four winds to see if any work has arrived [e.g. JAWS] (= way too latent & inefficient for me). 3) Assume that it is acceptable to have processors "spinning" looking for work ( = non-starter for me!) Unless anyone thinks there is a solution for this I will move on to consider a "Work Shrugging(tm)" strategy. Having the task-producing processor distribute excess load seems to me inherently capable of a much more efficient implementation. However a quick google didn't show up anything under the heading of "Work Shrugging" so any pointers to prior-art would be welcome. tx Tags I would have added if I was allowed to [work-stealing]

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• P6 Architecture - Register renaming aside, does the limited user registers result in more ops spent

  - by mrjoltcola

  I'm studying JIT design with regard to dynamic languages VM implementation. I haven't done much Assembly since the 8086/8088 days, just a little here or there, so be nice if I'm out of sorts. As I understand it, the x86 (IA-32) architecture still has the same basic limited register set today that it always did, but the internal register count has grown tremendously, but these internal registers are not generally available and are used with register renaming to achieve parallel pipelining of code that otherwise could not be parallelizable. I understand this optimization pretty well, but my feeling is, while these optimizations help in overall throughput and for parallel algorithms, the limited register set we are still stuck with results in more register spilling overhead such that if x86 had double, or quadruple the registers available to us, there may be significantly less push/pop opcodes in a typical instruction stream? Or are there other processor optmizations that also optimize this away that I am unaware of? Basically if I've a unit of code that has 4 registers to work with for integer work, but my unit has a dozen variables, I've got potentially a push/pop for every 2 or so instructions. Any references to studies, or better yet, personal experiences?

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• Compiler optimization causing the performance to slow down

  - by aJ

  I have one strange problem. I have following piece of code: template<clss index, class policy> inline int CBase<index,policy>::func(const A& test_in, int* srcPtr ,int* dstPtr) { int width = test_in.width(); int height = test_in.height(); double d = 0.0; //here is the problem for(int y = 0; y < height; y++) { //Pointer initializations //multiplication involving y //ex: int z = someBigNumber*y + someOtherBigNumber; for(int x = 0; x < width; x++) { //multiplication involving x //ex: int z = someBigNumber*x + someOtherBigNumber; if(soemCondition) { // floating point calculations } *dstPtr++ = array[*srcPtr++]; } } } The inner loop gets executed nearly 200,000 times and the entire function takes 100 ms for completion. ( profiled using AQTimer) I found an unused variable double d = 0.0; outside the outer loop and removed the same. After this change, suddenly the method is taking 500ms for the same number of executions. ( 5 times slower). This behavior is reproducible in different machines with different processor types. (Core2, dualcore processors). I am using VC6 compiler with optimization level O2. Follwing are the other compiler options used : -MD -O2 -Z7 -GR -GX -G5 -X -GF -EHa I suspected compiler optimizations and removed the compiler optimization /O2. After that function became normal and it is taking 100ms as old code. Could anyone throw some light on this strange behavior? Why compiler optimization should slow down performance when I remove unused variable ? Note: The assembly code (before and after the change) looked same.

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• Java: volatile guarantees and out-of-order execution

  - by WizardOfOdds

  Note that this question is solely about the volatile keyword and the volatile guarantees: it is not about the synchronized keyword (so please don't answer "you must use synchronize" for I don't have any issue to solve: I simply want to understand the volatile guarantees (or lack of guarantees) regarding out-of-order execution). Say we have an object containing two volatile String references that are initialized to null by the constructor and that we have only one way to modify the two String: by calling setBoth(...) and that we can only set their references afterwards to non-null reference (only the constructor is allowed to set them to null). For example (it's just an example, there's no question yet): public class SO { private volatile String a; private volatile String b; public SO() { a = null; b = null; } public void setBoth( @NotNull final String one, @NotNull final String two ) { a = one; b = two; } public String getA() { return a; } public String getB() { return b; } } In setBoth(...), the line assigning the non-null parameter "a" appears before the line assigning the non-null parameter "b". Then if I do this (once again, there's no question, the question is coming next): if ( so.getB() != null ) { System.out.println( so.getA().length ); } Am I correct in my understanding that due to out-of-order execution I can get a NullPointerException? In other words: there's no guarantee that because I read a non-null "b" I'll read a non-null "a"? Because due to out-of-order (multi)processor and the way volatile works "b" could be assigned before "a"? volatile guarantees that reads subsequent to a write shall always see the last written value, but here there's an out-of-order "issue" right? (once again, the "issue" is made on purpose to try to understand the semantics of the volatile keyword and the Java Memory Model, not to solve a problem).

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• Using jQuery delay() with separate elements

  - by boomturn

  I want to fake a simple animation on page load by sequentially revealing several pngs, each appearing instantly but with unique, precisely timed delay before the next one. Using the latest version of jQuery (1.4.2 at writing), which provides a delay method. My first (braindead) impulse was: $('#image1').show('fast').delay(800); $('#image2').show('fast').delay(1200); $('#image3').show('fast'); Of course all come up simultaneously. jQuery doc examples refer to a single item being chained, not handling multiple items. OK... try again using nested callbacks from show(): $('#image1').show('fast', function() { $('#image2').show('fast', function() { $('#image3').show('fast', function() { }); }); }); Looks ugly (imagine doing 10, also wonder what processor hit would be) but hey, it works sequentially! Without delay though. So... chain delay() after show() using a callback function from it (not even sure if it supports one): $('#image1').show('fast').delay(800, function() { $('#image2').show('fast').delay(1200, function() { $('#image3').show('fast'); }); }); Hm. Opposite result of what I thought might happen: the callback works, but still no delay. So... should I be using some combination of queue and delay instead of nested callbacks? jQuery doc examples for queue again only use one element for example. Guessing this would involve using a custom queue, but am uncertain how to implement this. Or maybe I'm missing a simple way? (For a simple problem!)

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• parameterized doctype in xsl:stylesheet

  - by Flavius

  How could I inject a --stringparam (xsltproc) into the DOCTYPE of a XSL stylesheet? The --stringparam is specified from the command line. I have several books in docbook5 format I want to process with the same customization layer, each book having an unique identifier, here "demo", so I'm running something like xsltproc --stringparam course.name demo ... for each book. Obviously the parameter is not recognized as such, but as verbatim text, giving the error: warning: failed to load external entity "http://edu.yet-another-project.com/course/$(course.name)/entities.ent" Here it is how I've tried, which won't work: <?xml version='1.0'?> <!DOCTYPE stylesheet [ <!ENTITY % myent SYSTEM "http://edu.yet-another-project.com/course/$(course.name)/entities.ent"> %myent; ]> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0"> <!-- the docbook template used --> <xsl:import href="http://docbook.org/ns/docbook/xhtml/chunk.xsl"/> <!-- processor parameters --> <xsl:param name="html.stylesheet">default.css</xsl:param> <xsl:param name="use.id.as.filename">1</xsl:param> <xsl:param name="chunker.output.encoding">UTF-8</xsl:param> <xsl:param name="chunker.output.indent">yes</xsl:param> <xsl:param name="navig.graphics">1</xsl:param> <xsl:param name="generate.revhistory.link">1</xsl:param> <xsl:param name="admon.graphics">1</xsl:param> <!-- here more stuff --> </xsl:stylesheet> Ideas?

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• Simple, fast SQL queries for flat files.

  - by plinehan

  Does anyone know of any tools to provide simple, fast queries of flat files using a SQL-like declarative query language? I'd rather not pay the overhead of loading the file into a DB since the input data is typically thrown out almost immediately after the query is run. Consider the data file, "animals.txt": dog 15 cat 20 dog 10 cat 30 dog 5 cat 40 Suppose I want to extract the highest value for each unique animal. I would like to write something like: cat animals.txt | foo "select $1, max(convert($2 using decimal)) group by $1" I can get nearly the same result using sort: cat animals.txt | sort -t " " -k1,1 -k2,2nr And I can always drop into awk from there, but this all feels a bit awkward (couldn't resist) when a SQL-like language would seem to solve the problem so cleanly. I've considered writing a wrapper for SQLite that would automatically create a table based on the input data, and I've looked into using Hive in single-processor mode, but I can't help but feel this problem has been solved before. Am I missing something? Is this functionality already implemented by another standard tool? Halp!

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• ARMv6 FIQ, acknowledge interrupt

  - by fastmonkeywheels

  I'm working with an i.mx35 armv6 core processor. I have Interrupt 62 configured as a FIQ with my handler installed and being called. My handler at the moment just toggles an output pin so I can test latency with a scope. With the code below, once I trigger the FIQ it continues forever as fast as it can, apparently not being acknowledged. I'm triggering the FIQ by means of the Interrupt Force Register so I'm assured that the source isn't triggering it this fast. If I disable Interrupt 62 in the AVIC in my FIQ routine the interrupt only triggers once. I have read the sections on the VIC Port in the ARM1136JF-S and ARM1136J-S Technical Reference Manual and it covers proper exit procedure. I'm only having one FIQ handler so I have no need to branch. The line that I don't understand is: STR R0, [R8,#AckFinished] I'm not sure what AckFinished is supposed to be or what this command is supposed to do. My FIQ handler is below: ldr r9, IOMUX_ADDR12 ldr r8, [r9] orr r8, #0x08 @ top LED str r8,[r9] @turn on LED bic r8, #0x08 @ top LED str r8,[r9] @turn off LED subs pc, r14, #4 IOMUX_ADDR12: .word 0xFC2A4000 @remapped IOMUX addr My handler returns just fine and normal system operation resumes if I disable it after the first go, otherwise it triggers constantly and the system appears to hang. Do you think my assumption is right that the core isn't acknowledging the AVIC or could there be another cause of this FIQ triggering?

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