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  • Why use Monte-Carlo method?

    - by Gili
    When should the Monte-Carlo method be used? For example, why did Joel decide to use the Monte-Carlo method for Evidence Based Scheduling instead of methodically processing all user data for the past year?

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  • Umbraco CMS stripping ALT tags from images when content saved

    - by Yucel
    Umbraco CMS stripping ALT tags from images when content saved Umbraco is taking this < img alt="Your Title - for example Mr., Mrs., Ms." src="../media/21283/q16x16.gif" width="16" height="15" /> and turning it into this. <img alt="" src="/media/21283/q16x16.gif" width="16" height="15" rel="16,15" /> If I alter the alt tag after this processing then the alt tag is saved.

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  • BasicHTTPServer, SimpleHTTPServer and concurrency

    - by braindump
    I'm writing a small web server for testing purposes using python, BasicHTTPServer and SimpleHTTPServer. It looks like it's processing one request at a time. Is there any way to make it a little faster without messing around too deeply? Basicly my code looks as the following and I'd like to keep it this simple ;) os.chdir(webroot) httpd = BaseHTTPServer.HTTPServer(("", port), SimpleHTTPServer.SimpleHTTPRequestHandler) print("Serving directory %s on port %i" %(webroot, port) ) try: httpd.serve_forever() except KeyboardInterrupt: print("Server stopped.")

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  • any good free C DSP library?

    - by Juan
    Hi everybody I am developing an application to process geophysical signals; Right now I have done everything in octave and its digital signal processing toolbox, speed is not bad, however the application specifications say I need to port to the final algorithm to C; I am doing lots of filtering, re-sampling and signal manipulation/characterization with FFTs and cepstrums. do you know a good free C library for DSP packaged with filter design, resampling, fft, etc? Thanks a lot for any suggestion

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  • django internationalization doesn't work

    - by xRobot
    I have: created translation strings in the template and in the application view. run this command: django-admin.py makemessages -l it and the file it/LC_MESSAGES/django.po has been created run this command: django-admin.py compilemessages and I receive: processing file django.po in /home/jobber/Desktop/library/books/locale/it/LC_MESSAGES set the language code in settings.py: LANGUAGE_CODE = 'it-IT' but.... translation doesn't work !! I always see english text. Why ?

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  • java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory

    - by Sanjeev
    I am using My-eclipse and doing a struts project there is no syntax error but on starting tomcat server the following error appear in console. java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory and javax.servlet.UnavailableException: Parsing error processing resource path jndi:/localhost/strutspro/WEB-INF/struts-config.xml any idea whats the problem.

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  • Is there any performance comparison between Perl web frameworks?

    - by DVK
    I have seen mentions (which sounded like unsubstantiated opinions, and dated ones at that) that Embperl is the fastest Perl web framework. I was wondering if there's a consensus on the relative speed of the major stable Perl web frameworks, or ideally, some sort of fact-based performance comparisons between implementations of the same sample webapps, or individual functionalities (e.g. session handling or form data processing), etc...?

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  • Enable iPhone accelerometer while screen is locked..

    - by kamziro
    So apparently it is possible to keep the processor going processing stuff while the screen is locked, as indicated here: http://stackoverflow.com/questions/1551712/running-iphone-apps-while-in-sleep-mode However, after testing with the example code, UIAccelerometer will just stop giving value as soon as the device is locked pronto. Is there a way to force otherwise?

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  • Any ideas on a WCF Interceptor for a REST WebGet request to change the Url/Querystring parameters

    - by REA_ANDREW
    Does any one know of a way I can intercept a REST Get request inside WCF, so for example I could change the value of any of the querystring parameters. So I need to have some code run, prior to WCF Evaluating the UriTemplate of the WebGet attribute and be able to edit it, before returning the value which it will use to continue processing the request. Any help would be greatly appreciated Andrew

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  • Fast file search algorithm for IP addresses

    - by Dave Jarvis
    Question What is the fastest way to find if an IP address exists in a file that contains IP addresses sorted as: 219.93.88.62 219.94.181.87 219.94.193.96 220.1.72.201 220.110.162.50 220.126.52.187 220.126.52.247 Constraints No database (e.g., MySQL, PostgreSQL, Oracle, etc.). Infrequent pre-processing is allowed (see possibilities section) Would be nice not to have to load the file each query (131Kb) Uses under 5 megabytes of disk space File Details One IP address per line 9500+ lines Possible Solutions Create a directory hierarchy (radix tree?) then use is_dir() (sadly, this uses 87 megabytes)

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  • Business Intelligence Development Studio encounter error on Rendering

    - by user366796
    I try to develop a data processing extension for SSRS 2008 in order to access database through an entity framework. But when I copy and register the extension in BI Development Studio, it gives me an error message while loading the extension". I built it with targeting framework 4.0 by using Visual Studio 2010 because my data model class library was built with that version of target framework. Any help will be greatly appreciated. Thanks.

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  • Messagebox in ASP.NET 3.5 with AJAX

    - by Jim Beam
    I have a ASP.NET 3.5 web site with an AJAX update panel. I simply need to process some server side code and then issue a user prompt that says "Code processing complete". I know there is supposed to be support for Msgbox-esque methods in ASP.NET but I can't find them and any other JavaScript based solutions don't work effectively when you have an update panel. Help.

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  • django: search forms and redirect

    - by gruszczy
    After processing form from POST I should redirect, to prevent user from hitting back. However, I am using form to determine search query on a database, so I need to either pass params to the redirected site or the result of a search. Or maybe there is some other good practice, how to solve this problem? Maybe in this situation I am allowed not to redirect (nothing happens, if user performs search again).

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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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  • Can Ghostscript to start numbering pages from zero?

    - by SuZi
    I am using Ghostscript to convert a multi-page pdf to individual jpg files and can get it to output the files numbered like page_%03d.jpg but it always starts at page_001.jpg and i need it to start numbering the output files starting from page_000.jpg. Is there a setting i can use to get Ghostscript to start at zero or am i going to have to rename all the files after processing?

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  • Why is mod_wsgi not able to write data? IOError: failed to write data

    - by BryanWheelock
    What could be causing this error: $ sudo tail -n 100 /var/log/apache2/error.log' [Wed Dec 29 15:20:03 2010] [error] [client 220.181.108.181] mod_wsgi (pid=20343): Exception occurred processing WSGI script '/home/username/public_html/idm.wsgi'. [Wed Dec 29 15:20:03 2010] [error] [client 220.181.108.181] IOError: failed to write data Here is the WSGI script: $ cat public_html/idm.wsgi import os import sys sys.path.append('/home/username/public_html/IDM_app/') os.environ['DJANGO_SETTINGS_MODULE'] = 'settings' import django.core.handlers.wsgi application = django.core.handlers.wsgi.WSGIHandler() Why would Django not be able to write data? I'm running Django 1.2.4

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  • Testing Paypal error messages using ActiveMerchant

    - by vrish88
    Hello, Is there a way to test your application's processing and handling of Paypal generated credit card errors? I'd like to verify that my application can handle a declined credit card or something like that. So is there a way to have Paypal send an error message? Or would it be better to generate a stub and use it in the testing environment? If this is the better way, how would one generate a stub? Thanks!

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  • Using Amazon's EBS for MySQL hot backup

    - by flybywire
    What are your experiences using Amazons EBS snapshot features for MySql hot backups. I have a database running a batch processing job in ec2. I backup with EBS snapshot. So far the backups looks consistent. But I am afraid they "will stop being consistent as soon as I stop checking" (Uncertainty principle). What are your experiences with backuping relational databases (and mysql in particular) with ebs snapshot?

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  • Camel-like integration component for Ruby

    - by Matthias Hryniszak
    Hi, I'm in need to get some integration work done in my ruby application. My main focus is web services and ActiveMQ integration (the systems I'm going to connect to are mainly written in Java). I was wondering if there's something that resembles the capabilities of Camel in Ruby? All I need is something that'll let me define routing between incoming data from those sources I mentioned above, do some pre-processing and post them back somewhere else. Thanks, Matthias

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  • Secure online registration form to capture credit card info

    - by baraider
    We have used Google form, Wufoo form to try to securely capture the info for IN-HOUSE processing. Google form is unreliable and often blocked behind firm's firewall. Wufoo does not allow storing CC info in their database What is service or other alternative for us to securely store the cc info. The purpose is to have people manually process the registration. Once the payment goes through, we notify the customer and remove the CC info from our database.

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