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  • Codaset, Codebasehq, Unfuddle, Trac or Redmine?

    - by Alex
    I have a handful of small Git repositories I would like to host remotely. They're all private projects, most of them in Java. Codaset, Codebasehq, Unfuddle, Trac, Redmine.. There seems to be an abundance of solutions out there. They're all packed with features and useful functionality. Putting aside pricing and the glossy layouts, what is the best way of comparing these options?

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  • What is the fastest cyclic synchronization in Java (ExecutorService vs. CyclicBarrier vs. X)?

    - by Alex Dunlop
    Which Java synchronization construct is likely to provide the best performance for a concurrent, iterative processing scenario with a fixed number of threads like the one outlined below? After experimenting on my own for a while (using ExecutorService and CyclicBarrier) and being somewhat surprised by the results, I would be grateful for some expert advice and maybe some new ideas. Existing questions here do not seem to focus primarily on performance, hence this new one. Thanks in advance! The core of the app is a simple iterative data processing algorithm, parallelized to the spread the computational load across 8 cores on a Mac Pro, running OS X 10.6 and Java 1.6.0_07. The data to be processed is split into 8 blocks and each block is fed to a Runnable to be executed by one of a fixed number of threads. Parallelizing the algorithm was fairly straightforward, and it functionally works as desired, but its performance is not yet what I think it could be. The app seems to spend a lot of time in system calls synchronizing, so after some profiling I wonder whether I selected the most appropriate synchronization mechanism(s). A key requirement of the algorithm is that it needs to proceed in stages, so the threads need to sync up at the end of each stage. The main thread prepares the work (very low overhead), passes it to the threads, lets them work on it, then proceeds when all threads are done, rearranges the work (again very low overhead) and repeats the cycle. The machine is dedicated to this task, Garbage Collection is minimized by using per-thread pools of pre-allocated items, and the number of threads can be fixed (no incoming requests or the like, just one thread per CPU core). V1 - ExecutorService My first implementation used an ExecutorService with 8 worker threads. The program creates 8 tasks holding the work and then lets them work on it, roughly like this: // create one thread per CPU executorService = Executors.newFixedThreadPool( 8 ); ... // now process data in cycles while( ...) { // package data into 8 work items ... // create one Callable task per work item ... // submit the Callables to the worker threads executorService.invokeAll( taskList ); } This works well functionally (it does what it should), and for very large work items indeed all 8 CPUs become highly loaded, as much as the processing algorithm would be expected to allow (some work items will finish faster than others, then idle). However, as the work items become smaller (and this is not really under the program's control), the user CPU load shrinks dramatically: blocksize | system | user | cycles/sec 256k 1.8% 85% 1.30 64k 2.5% 77% 5.6 16k 4% 64% 22.5 4096 8% 56% 86 1024 13% 38% 227 256 17% 19% 420 64 19% 17% 948 16 19% 13% 1626 Legend: - block size = size of the work item (= computational steps) - system = system load, as shown in OS X Activity Monitor (red bar) - user = user load, as shown in OS X Activity Monitor (green bar) - cycles/sec = iterations through the main while loop, more is better The primary area of concern here is the high percentage of time spent in the system, which appears to be driven by thread synchronization calls. As expected, for smaller work items, ExecutorService.invokeAll() will require relatively more effort to sync up the threads versus the amount of work being performed in each thread. But since ExecutorService is more generic than it would need to be for this use case (it can queue tasks for threads if there are more tasks than cores), I though maybe there would be a leaner synchronization construct. V2 - CyclicBarrier The next implementation used a CyclicBarrier to sync up the threads before receiving work and after completing it, roughly as follows: main() { // create the barrier barrier = new CyclicBarrier( 8 + 1 ); // create Runable for thread, tell it about the barrier Runnable task = new WorkerThreadRunnable( barrier ); // start the threads for( int i = 0; i < 8; i++ ) { // create one thread per core new Thread( task ).start(); } while( ... ) { // tell threads about the work ... // N threads + this will call await(), then system proceeds barrier.await(); // ... now worker threads work on the work... // wait for worker threads to finish barrier.await(); } } class WorkerThreadRunnable implements Runnable { CyclicBarrier barrier; WorkerThreadRunnable( CyclicBarrier barrier ) { this.barrier = barrier; } public void run() { while( true ) { // wait for work barrier.await(); // do the work ... // wait for everyone else to finish barrier.await(); } } } Again, this works well functionally (it does what it should), and for very large work items indeed all 8 CPUs become highly loaded, as before. However, as the work items become smaller, the load still shrinks dramatically: blocksize | system | user | cycles/sec 256k 1.9% 85% 1.30 64k 2.7% 78% 6.1 16k 5.5% 52% 25 4096 9% 29% 64 1024 11% 15% 117 256 12% 8% 169 64 12% 6.5% 285 16 12% 6% 377 For large work items, synchronization is negligible and the performance is identical to V1. But unexpectedly, the results of the (highly specialized) CyclicBarrier seem MUCH WORSE than those for the (generic) ExecutorService: throughput (cycles/sec) is only about 1/4th of V1. A preliminary conclusion would be that even though this seems to be the advertised ideal use case for CyclicBarrier, it performs much worse than the generic ExecutorService. V3 - Wait/Notify + CyclicBarrier It seemed worth a try to replace the first cyclic barrier await() with a simple wait/notify mechanism: main() { // create the barrier // create Runable for thread, tell it about the barrier // start the threads while( ... ) { // tell threads about the work // for each: workerThreadRunnable.setWorkItem( ... ); // ... now worker threads work on the work... // wait for worker threads to finish barrier.await(); } } class WorkerThreadRunnable implements Runnable { CyclicBarrier barrier; @NotNull volatile private Callable<Integer> workItem; WorkerThreadRunnable( CyclicBarrier barrier ) { this.barrier = barrier; this.workItem = NO_WORK; } final protected void setWorkItem( @NotNull final Callable<Integer> callable ) { synchronized( this ) { workItem = callable; notify(); } } public void run() { while( true ) { // wait for work while( true ) { synchronized( this ) { if( workItem != NO_WORK ) break; try { wait(); } catch( InterruptedException e ) { e.printStackTrace(); } } } // do the work ... // wait for everyone else to finish barrier.await(); } } } Again, this works well functionally (it does what it should). blocksize | system | user | cycles/sec 256k 1.9% 85% 1.30 64k 2.4% 80% 6.3 16k 4.6% 60% 30.1 4096 8.6% 41% 98.5 1024 12% 23% 202 256 14% 11.6% 299 64 14% 10.0% 518 16 14.8% 8.7% 679 The throughput for small work items is still much worse than that of the ExecutorService, but about 2x that of the CyclicBarrier. Eliminating one CyclicBarrier eliminates half of the gap. V4 - Busy wait instead of wait/notify Since this app is the primary one running on the system and the cores idle anyway if they're not busy with a work item, why not try a busy wait for work items in each thread, even if that spins the CPU needlessly. The worker thread code changes as follows: class WorkerThreadRunnable implements Runnable { // as before final protected void setWorkItem( @NotNull final Callable<Integer> callable ) { workItem = callable; } public void run() { while( true ) { // busy-wait for work while( true ) { if( workItem != NO_WORK ) break; } // do the work ... // wait for everyone else to finish barrier.await(); } } } Also works well functionally (it does what it should). blocksize | system | user | cycles/sec 256k 1.9% 85% 1.30 64k 2.2% 81% 6.3 16k 4.2% 62% 33 4096 7.5% 40% 107 1024 10.4% 23% 210 256 12.0% 12.0% 310 64 11.9% 10.2% 550 16 12.2% 8.6% 741 For small work items, this increases throughput by a further 10% over the CyclicBarrier + wait/notify variant, which is not insignificant. But it is still much lower-throughput than V1 with the ExecutorService. V5 - ? So what is the best synchronization mechanism for such a (presumably not uncommon) problem? I am weary of writing my own sync mechanism to completely replace ExecutorService (assuming that it is too generic and there has to be something that can still be taken out to make it more efficient). It is not my area of expertise and I'm concerned that I'd spend a lot of time debugging it (since I'm not even sure my wait/notify and busy wait variants are correct) for uncertain gain. Any advice would be greatly appreciated.

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  • Relative Footer with Absolute DIV Elements

    - by Alex
    Hi, I'm creating a wordpress theme where the header and the nav bar are positioned absolutely, and the footer needs to be positioned relatively depending on the height of the content on each page. When I try to set the footer's positioning to relative, however, it appears at the top of the page underneath the content. All elements are in a relatively positioned container. Is there any way to fix this, or to dynamically get the height of the content plus the header and nav bar? The structure of the page is as follows: <div id="container"> <div id="header"> </div> <div id="navbar"> </div> <div id="content"> Dynamically generated and variable height content here. </div> <div id="footer"> </div> </div> And the relevant css is: #container { position: relative; margin:0px auto; width: 945px; text-align: left; } #header, #navbar{ background-color: #FFFFFF; position: absolute; margin-right: auto; margin-left: auto; width: 945px; float: left; } #footer { height: 35px; margin-right: auto; margin-left: auto; width: 945px; position: relative; padding-top: 20px } Thanks for the help.

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  • Separation of multipage tiff with compression "CCITT T.6" very slow

    - by Alex
    I need to separate multiframe tiff files, and use the following method: public static Image[] GetFrames(Image sourceImage) { Guid objGuid = sourceImage.FrameDimensionsList[0]; FrameDimension objDimension = new FrameDimension(objGuid); int frameCount = sourceImage.GetFrameCount(objDimension); Image[] images = new Image[frameCount]; for (int i = 0; i < frameCount; i++) { MemoryStream ms = new MemoryStream(); sourceImage.SelectActiveFrame(objDimension, i); sourceImage.Save(ms, ImageFormat.Tiff); images[i] = Image.FromStream(ms); } return images; } It works fine, but if the source image was encoded using the CCITT T.6 compression, separating a 20-frame-file takes up to 15 seconds on my 2,5ghz CPU.(edit: One core is at 100% during the process) When saving the images afterward to a single file using standard compression (LZW), the separation time of the LZW-file is under 1 second. Saving with CCITT compression also takes very long. Is there a way to speed up the process?

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  • How to Increase the time till a read timeout error occurs?

    - by Alex
    Hi all. I've written in PHP a script that takes a long time to execute [Image processing for thousands of pictures]. It's a meter of hours - maybe 5. After 15 minutes of processing, I get the error: ERROR The requested URL could not be retrieved The following error was encountered while trying to retrieve the URL: The URL which I clicked Read Timeout The system returned: [No Error] A Timeout occurred while waiting to read data from the network. The network or server may be down or congested. Please retry your request. Your cache administrator is webmaster. What I need is to enable that script to run for much longer. Now, here are all the technical info: I'm writing in PHP and using the Zend Framework. I'm using Firefox. The long script that is processed is done after clicking a link. Obviously, since the script is not over I see the web page on which the link was and the web browser writes "waiting for ...". After 15 minutes the error occurs. I tried to make changes to Firefox threw about:config but without any success. I don't know, but the changes might be needed somewhere else. So, any ideas? Thanks ahead.

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  • Flash vs. Ajax Abilities

    - by Alex
    Hey everyone. I want to develop an application that does a bunch of cool stuff. The first thing that I need in it is to get information about the page a person is browsing. With that said, I need for example to know how long a user stayed in a page and where was the scrollbar. While getting that data, It's all saved to a database. The thing is, I prefer doing that in Flash [although I have no experience in it] over Ajax since I want to hide the code - which as far as I know not possible in Javascript/Ajax. So, can I do all that in Flash? - Read the content of the page, get the status of the scroll bar.. Plus, I then need to go threw the gathered information that is saved in the database. Since there could be many calculations i thought C++ .Net is better than PHP [which I know better]. Is that all possible or am I just crazy? :) Thanks ahead.

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  • Anything wrong with spamming GC.KeepAlive(KeyboardHookPointer)?

    - by Alex
    GC.KeepAlive() References the specified object, which makes it ineligible for garbage collection from the start of the current routine to the point where this method is called. Not really sure about what GC.KeepAlive does other than simply store a reference so the Garbage Collector doesn't collect the object. But does calling GC.KeepAlive() on an object permanently keep an object from being collected? Or do you have to re-call GC.KeepAlive() every so often (and if so, how often)? I want to keep my keyboard hook alive.

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  • Linux: page faults and network filesystems

    - by Alex B
    If a Linux system runs out of physical memory, does it drop inactive executable code pages? I assume the answer is yes, since there is no reason to keep them in swap, so they are simply discarded and re-loaded if necessary (as far as I know, that's what FreeBSD does). If the above is true for Linux, my question is, how does it handle executables run from network filesystems (e.g. NFS)? Does it go and fetch executable pages over the network if there is a page fault?

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  • warning: incompatible implicit declaration of built-in function ‘xyz’

    - by Alex Reynolds
    I'm getting a number of these warnings when compiling a few binaries: warning: incompatible implicit declaration of built-in function ‘strcpy’ warning: incompatible implicit declaration of built-in function ‘strlen’ warning: incompatible implicit declaration of built-in function ‘exit’ To try to resolve this, I have added #include <stdlib.h> at the top of the C files associated with this warning, in addition to compiling with the following flags: CFLAGS = -fno-builtin-exit -fno-builtin-strcat -fno-builtin-strncat -fno-builtin-strcpy -fno-builtin-strlen -fno-builtin-calloc I am using GCC 4.1.2: $ gcc --version gcc (GCC) 4.1.2 20080704 What should I do to resolve these warnings? Thanks for your advice.

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  • ASP.NET MVC: ModelState vs. ModelStateDictionary

    - by Alex
    Hello, I have a service which has a method that's called when a certain controller method is triggered. My service returns a custom result object PlacementResult in which I want to communicate errors that may have happened (validation) back to the controller method. Should PlacementResult have a ModelState or a ModelStateDictionary to communicate errors back to the controller (and finally view)? How would I string this together? Finally, how do I get the ModelState/ModelStateDictionary (whichever you tell me I should choose) back into the view (highlighting the appropriate text box, show the error message etc.)? Thank you !

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  • Help with password complexity regex

    - by Alex
    I'm using the following regex to validate password complexity: /^.*(?=.{6,12})(?=.*[0-9]{2})(?=.*[A-Z]{2})(?=.*[a-z]{2}).*$/ In a nutshell: 2 lowercase, 2 uppercase, 2 numbers, min length is 6 and max length is 12. It works perfectly, except for the maximum length, when I'm using a minimum length as well. For example: /^.*(?=.{6,})(?=.*[0-9]{2})(?=.*[A-Z]{2})(?=.*[a-z]{2}).*$/ This correctly requires a minimum length of 6! And this: /^.*(?=.{,12})(?=.*[0-9]{2})(?=.*[A-Z]{2})(?=.*[a-z]{2}).*$/ Correctly requires a maximum length of 12. However, when I pair them together as in the first example, it just doesn't work!! What gives? Thanks!

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  • Best practices for Subversion and Visual Studio projects

    - by Alex Marshall
    I've recently started working on various C# projects in Visual Studio as part of a plan for a large scale system that will be used to replace our current system that's built from a cobbling-together of various programs and scripts written in C and Perl. The projects I'm now working on have reached critical mass for being committed to subversion. I was wondering what should and should not be committed to the repository for Visual Studio projects. I know that it's going to generate various files that are just build-artifacts and don't really need to be committed, and I was wondering if anybody had any advice for properly using SVN with Visual Studio. At the moment, I'm using an SVN 1.6 server with Visual Studio 2010 beta. Any advice, opinions are welcome.

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  • Does .net calling COM which in turn calls other .net COM object works when using SxS and manifest fi

    - by Alex Shnayder
    I have a .net application calling to a COM component (C++) which in turn calls to another COM object implemented in .NET. This application is using Windows SxS capabilities and does not register any of it's COM components. Not the one written in C++, and not the one written in .net. This first call to the C++ COM component works fine. But when the C++ COM component calls to the .net one, it fails with class not registered. I have tried creating a small C++ app with a manifest file which calls the .net component and it works. It seems that when the flow is .net - COM NATIVE - .NET COM. Then SxS breaks and does not work. When looking at Fusion Logs (assembly loading logs) I see that no one is even attempting to resolve the .NET COM assembly. Is this SxS scenario even supposed to work (I think it does supposed to work)? If yes, then what can I be doing wrong ?

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  • How to assemble a multi-project ant build system

    - by Alex Worden
    At my new gig, they use Ant and cannot be persuaded to move to Maven. I've looked everywhere for a decent example of how a multi-project ant build system should be assembled. The apache site falls short. I'm looking specifically for best practices to: Automatically build local projects that are dependencies of a project Share artifacts from project to their dependents Export a project's dependencies and generated artifacts (jars) to be inherited by dependent projects Share third-party dependencies between projects I'm sure I can do all this without using Ivy - what did people do before Ivy? I really don't want to have to set up a corporate repository or rely on external repositories - the engineers here are really against that and have all their third-party jars checked into src control. Can anyone point me at a good open source example of a multi-project ant build?

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  • Best practices for building a simple, scalable cluster on Amazon EC2 for a Java web app

    - by Alex B
    I want to build a Java web app and deploy it on EC2. It will be written in Java and will use MySQL. I was hoping to get some pointers on the actual deployment process and configuration. In particular I'm interested in the following topics: machine images (diy vs ready made) mysql replication and backup to S3 ways of deploying and redeploying the app to EC2 without interruptions firewalls? load balancing and auto scaling cloudtools (or alternative tools)

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  • JavaScript types

    - by Alex Ivasyuv
    Hi, as per http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-262.pdf JavaScript has 6 types: undefined, null, boolean, string, number, object. var und; console.log(typeof und); // <-- undefined var n = null; console.log(typeof n); // <--- **object**! var b = true; console.log(typeof b); // <-- boolean var str = "myString" console.log(typeof str); // <-- string var int = 10; console.log(typeof int); // <-- number var obj = {} console.log(typeof obj); // <-- object Question 1: Why null is object type, if it has to be a null type. Question 2: What about function? var f = function() {}; console.log(typeof f); // <-- function Variable f has "function" type. Why it doesn't specified in specification as separate type. Thanks,

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  • JAXB, BigDecimal or double?

    - by Alex
    I working on different web-services, and I always use WSDL First. JAXB generates for a Type like: <xsd:simpleType name="CurrencyFormatTyp"> <xsd:restriction base="xsd:decimal"> <xsd:totalDigits value="13"/> <xsd:fractionDigits value="2"/> <xsd:minInclusive value="0.01"/> </xsd:restriction> </xsd:simpleType> a Java binding type BigDecimal (as it's mentioned in JAXB specification). When I then do some simple arithmetic operation with values of the type double (which are stored in a database and mapped via hibernate to the type double) I run into trouble. <ns5:charge>0.200000000000000011102230246251565404236316680908203125</ns5:charge> <ns5:addcharge>0.0360000000000000042188474935755948536098003387451171875</ns5:addcharge> <ns5:tax>0.047199999999999998900879205621095024980604648590087890625</ns5:tax> <ns5:totalextax>0.2360000000000000153210777398271602578461170196533203125</ns5:totalextax> What would be the right way? Convert all my values into double (JAXB binding from BigDecimal to double) Hibernate mapping double to Bigdecimal and do all my arithmetic operations in one object type.

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  • How important is managing memory in Objective-C?

    - by Alex Mcp
    Background: I'm (jumping on the bandwagon and) starting learning about iPhone/iPad development and Objective-C. I have a great background in web development and most of my programming is done in javascript (no libraries), Ruby, and PHP. Question: I'm learning about allocating and releasing memory in Objective-C, and I see it as quite a tricky task to layer on top of actually getting the farking thing to run. I'm trying to get a sense of applications that are out there and what will happen with a poorly memory-managed program. A) Are apps usually released with no memory leaks? Is this a feasible goal, or do people more realistically just excise the worst offenders and that's ok? B) If I make an NSString for a title of a view, let's say, and forget to deallocate it it, does this really only become a problem if I recreate that string repeatedly? I imagine what I'm doing is creating an overhead of the memory needed to store that string, so it's probably quite piddling (a few bytes?) However if I have a rapidly looping cycle in a game that 'leaks' an int every cycle or something, that would overflow the app quite quickly. Are these assumptions correct? Sorry if this isn't up the community-wiki alley, I'm just trying to get a handle on how to think about memory and how careful I'll need to be. Any anecdotes or App Store-submitted app experiences would be awesome to hear as well.

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  • Tomcat JAXB 1 and 2 linkage error

    - by Alex
    I'm running a tomcat 6, spring, apache cxf webservice, know it is a must to add one third party library to my webapp to fulfill an order. I have jaxb-impl-2.1.12.jar for apache cxf in WEB-INF/lib folder and the new library which contains the JAXB 1.0 runtime. JAXB 2 ist used by apache cxf for dynamic clients (i need them). So is there a possibility to run the webapps with both libraries? Error: Caused by: java.lang.LinkageError: You are trying to run JAXB 2.0 runtime but you have old JAXB 1.0 runtime earlier in the classpath. Please remove the JAXB 1.0 runtime for 2.0 runtime to work correctly.

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  • JQuery AJAX is not sending UTF-8 to my server, only in IE.

    - by alex
    I am sending UTF-8, japanese text, to my server. It works in Firefox. My access.log and headers are: /ajax/?q=%E6%BC%A2%E5%AD%97 Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7 Content-Type application/x-www-form-urlencoded; charset=UTF-8 Howeer, in IE8, my access.log says: /ajax/?q=?? For some reason, IE8 is turning my AJAX call into question marks. Why!? I added the scriptCharset and ContentType according to some tutorials, but still no luck. And this is my code: $.ajax({ >---method:"get", >---url:"/ajax/", scriptCharset: "utf-8" , contentType: "application/x-www-form-urlencoded; charset=UTF-8", >---data:"q="+query ... ...

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