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• Which parallel sorting algorithm has the best average case performance?

  - by Craig P. Motlin

  Sorting takes O(n log n) in the serial case. If we have O(n) processors we would hope for a linear speedup. O(log n) parallel algorithms exist but they have a very high constant. They also aren't applicable on commodity hardware which doesn't have anywhere near O(n) processors. With p processors, reasonable algorithms should take O(n/p log n/p) time. In the serial case, quick sort has the best runtime complexity on average. A parallel quick sort algorithm is easy to implement (see here and here). However it doesn't perform well since the very first step is to partition the whole collection on a single core. I have found information on many parallel sort algorithms but so far I have not seen anything pointing to a clear winner. I'm looking to sort lists of 1 million to 100 million elements in a JVM language running on 8 to 32 cores.

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• How to create an ARGB_8888 pixel value?

  - by vidstige

  Say I want to create an array of pixel values to pass into the createBitmap method described here. I have three int values r, g, b in the range 0 - 0xff. How do I transform those into a opaque pixel p? Does the alpha channel go in the high byte or the low byte? I googled up the documentation but it only states that: Each pixel is stored on 4 bytes. Each channel (RGB and alpha for translucency) is stored with 8 bits of precision (256 possible values.) This configuration is very flexible and offers the best quality. It should be used whenever possible. So, how to write this method? int createPixel(int r, int g, int b) { retrurn ? }

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• How to pass some data to JQuery AJAX in CAKEPHP

  - by kwokwai

  Hi all, I am learning how to use JQuery to help check data availability. To start with it, I wrote a few lines of codes using cakePHP. I have written a function in a Controller for checking data input, and the URL is like this: http://www.mywebsite.com/controllers/action/avariable I was trying to pass the value in a Input TextBox field using the JQuery Ajax to the URL above,but I don't know why it is not working in passing a variable to the Controller's action. Could you help me out please? <Script language="javascript"> //<!-- $(document).ready(function(){ $(document).change(function() { var usr = $("#data\\[User\\]\\[name\\]").val(); if(usr.length >= 3){ $("#username").append('<span><img align="absmiddle" src="loader.gif" />Checking</span>'); $.ajax({ type: "POST", url: "http://www.mywebsite.com/controllers/action/", data: usr, success: function(msg){ if(msg == 'OK') { $("#username").append('<span><img align="absmiddle" src="accepted.png"/></span>'); } else { $("#username").append('<span>'+msg+'</span>'); } } }); } else { $("#username").append('<span>The username should have at least 3 characters.</span>'); } }); }); //--> </Script> <form name="adduser" id="adduser" method="post" action="/controllers/action2"> <table border=0 width="100%"> <tr> <td>Username</td> <td> <div id="username"> <input type=text name="data[User][name]" id="data[User][name]"> </div> </td> </tr> <tr> <td> <input type="submit" value="Send"> </td> </tr> </table> </form>

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• How to find root cause for "too many connections" error in MySQL/PHP

  - by Nir

  I'm running a web service which runs algorithms that serve millions of calls daily and run some background processing as well. Every now and than I see "Too many connections" error in attempts to connect to the MySQL box" for a few seconds. However this is not necessarily attributed to high traffic times or anything I can put my finger on. I want to find the bottleneck causing it. Other than in the specific times this happens the server isn't too loaded in terms of CPU and Memory, and has 2-3 connections (threads) open and everything works smoothly. (I use Zabbix for monitoring) Any creative ideas on how to trace it?

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• Hard drive randomly sppeeding up

  - by Glenn Taylor

  Having a weird issue with my hard drive. Running Windows 7 with an I5 processor. At random times the hard drive will start running at top speed and gradually return to normal over the next two minutes or so. Going to Resource Monitor it shows a variety of things with high read or write numbers. Log files NTFS volume log, Windows prefetch, System/user/appdata, and Program data Norton are the usual top ones listed. This just started about three months ago although the computer is about 3 years old. Have run in safe mode with internet over the weekend going to all of my usual sites with no such speed up. Question 1 - what can be causing this? Question 2 - how can I find out where data is being sent(especially if over the net)? Thank you.

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• What's a good FOSS java servlet session replication solution

  - by Bossy Joe

  I work on a very high volume public website running on Tomcat 5.5. Currently we require stickiness to a particular server in order to maintain session. I'd like to start replicating session, but have had trouble finding a good FOSS solution. I've written my own Manager (using memcached as the store) but am having trouble dealing with race conditions if more than one server is handling the requests for the same user. Is there a solution out there I should be looking at? I'm looking for not just something that works as a fallback if stickiness fails, but that would work if user requests are regularly spread to multiple servers.

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• Best keyboards for emacs?

  - by catphive

  For emacs users out there, what are your recommended keyboards? Bonus points for keyboards that: Have no capslock key. Instead, a control key in that position. Alt keys that are closer to the center, and easier to use with meta key combos. I find alt keys too far to the left to be a bit awkward to hit with my thumb in some key combos. Help ergonomically with emacs in other ways. I'm not a huge fan of model M style high and clacky keys. I instead prefer laptop style flat keys; however, I'm not disqualifying either category.

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• How should i draw text and shapes in wpf and C#?

  - by peterhu

  I want to do basic WPF graphics, i.e. rectangles, lines, circles and text. When should I use Drawing and when should I use a DrawingVisual? I have some code that uses Drawing and I render those to a DrawingImage and display that in an image control. Is this the right way? I could not see how to add text to a drawing. I had trouble positioning it too. Should I be rendering to a Canvas? I have some code that uses DrawingVisual and writes to a DrawingContext. That is like WinForms. Is this the recommended way? Do you have any high level advice on which APIs to use for basic graphics and labels? Will they options work on Silver Light and Desktop?

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• How can I change column fore color in DataGridview as per condition?

  - by Ashish

  hi, i have one table like employee and one of its row is 'status' if status value is 'approve' then i want to show that row in green color and else i want to show it in red color. i have tried following but not working if (e.Row.RowType == DataControlRowType.Header) { string status = DataBinder.Eval(e.Row.DataItem, "IsApprove").ToString(); if (status == "pending") { e.Row.ForeColor = System.Drawing.Color.Red; // Change the row's Text color } } ALSO THIS ONE private void gvleavedetail_cellformatting(object sender, datagridviewcellformattingeventargs e) { // if the column is the artist column, check the // value. if (this.gvleavedetail.columns[e.columnindex].name == "artist") { if (e.value != null) { // check for the string "pink" in the cell. string stringvalue = (string)e.value; stringvalue = stringvalue.tolower(); if (stringvalue == "high") { e.cellstyle.backcolor = color.pink; } } } But in this case i'm getting error for datagridviewcellformattingeventargs I'm using VS2010

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• Java Web Server with Jetty - TCP Connections Taking Long

  - by daysleeper

  I have an application with fairly high traffic (20K req/min) running on the JVM with a Jetty servlet container on Ubuntu. Below is my Jetty configuration: 10 20 2000 2 When I analyze the network traffic, I realize that sometimes it is taking long to establish TCP connections on the port that Jetty is running. The long connections are varying between 3.0s and 9.0s. The port is configured to accept MAX number of TCP connections. Do you know what might be causing the delay in accepting connections? Thanks

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• Spring 3.0 REST implementation or Jersey?

  - by hnilsen

  Hi, SO! I'm currently trying to figure out which implementation of JSR-311 I'm going to recommend further up the food chain. I've pretty much narrowed it down to two options - Spring 3.0 with it's native support for REST - or use Sun's own Jersey (Restlets might also be an option). To me it doesn't seem to be much of a difference in the actual syntax, but there might be issues with performance that I haven't figured out yet. The service is meant to replace some heavy-duty EJB's and make a RESTful Webservice instead. The load is expected to be rather high, up in the 100k users per day (max) range, but will be seriously load balanced. Thanks for all your insights.

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• Improving the performance of an nHibernate Data Access Layer.

  - by Amitabh

  I am working on improving the performance of DataAccess Layer of an existing Asp.Net Web Application. The scenerios are. Its a web based application in Asp.Net. DataAccess layer is built using NHibernate 1.2 and exposed as WCF Service. The Entity class is marked with DataContract. Lazy loading is not used and because of the eager-fetching of the relations there is huge no of database objects are loaded in the memory. No of hits to the database is also high. For example I profiled the application using NHProfiler and there were about 50+ sql calls to load one of the Entity object using the primary key. I also can not change code much as its an existing live application with no NUnit test cases at all. Please can I get some suggestions here?

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• How do you deal with the more mundane parts of programming tasks?

  - by Uri

  My experience as a developer is that many projects or tickets are a mix of a short and focused very interesting task (e.g., designing some API or a platform to solve something) and a lot of repetitive and mundane tasks that cannot be automated (such as certain refactorings to use the API or platform, implementation of certain tests, some GUI handling, etc). I believe that this is the nature of our profession, unless we are high-level architects or managements and can delegate this work. The only item in my personal arsenal when dealing with these tasks is to devote some of my attention to radio or audiobooks (preferably not in English as I find it hard to concentrate on two "streams" of English at the same time). I maintain sufficient attention to carry the task and don't lose concentration as fast. I'm wondering how others cope with these and maintain concentration.

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• Alter top and bottom borders of Dojo/Dijit Dialog and ContentPane

  - by Joe Zitzelberger

  I have a Dojo/Dijit Dialog that contains a FORM. There is a top border between the title bar and the content, and a bottom border below the content. Both are about 19 or 20 pixels high and colored #eeeeee. I can't find these borders in the CSS anywhere -- actually, neither can the IE Developer Toolbar -- they just don't seem to exist as elements. I suspect that Dijit is adding these programatically. Is there any way to just remove these borders? I just want my content to consume all of the dialog area below the title bar. TIA

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• How to structure opening hours of a place? May-be there's even an ontology for it?

  - by Ago

  Does anyone know any ontology which specifies opening hours of places? For example, I have a museum, which has 2 seasons. For low season (season start and end is specified), it is opened 10.00 - 18.00 on weekdays and 10-16 on saturday (on sunday it's closed), for high season it's opened 10-20 on weekdays and 10-18 on weekend. If there is no ontology, may-be people have experience, how best to structure information like that? I'm describing information in RDF. But whatever comments are welcome (even if you have relational database which holds given data). Thanks

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• Where is Python support for PEM + RSA + DES3?

  - by jasonjs

  I need a Python library that supports PEM files and both RSA signing and DES3 encryption. pycrypto doesn't seem to support PEM, and its mechanism for loading existing keys is undocumented and cryptic. m2crypto doesn't seem to support DES/DES3, oddly. I've been running an openssl subprocess, but I'd rather have something built in and preferably fast. Does this exist? (Failing that, I hesitate to ask, but are there high-level enough C apis available for this that I could write a special-purpose extension without killing myself/introducing vulns?)

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• Fast, cross-platform timer?

  - by dsimcha

  I'm looking to improve the D garbage collector by adding some heuristics to avoid garbage collection runs that are unlikely to result in significant freeing. One heuristic I'd like to add is that GC should not be run more than once per X amount of time (maybe once per second or so). To do this I need a timer with the following properties: It must be able to grab the correct time with minimal overhead. Calling core.stdc.time takes an amount of time roughly equivalent to a small memory allocation, so it's not a good option. Ideally, should be cross-platform (both OS and CPU), for maintenance simplicity. Super high resolution isn't terribly important. If the times are accurate to maybe 1/4 of a second, that's good enough. Must work in a multithreaded/multi-CPU context. The x86 rdtsc instruction won't work.

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• ANY material writen in/for DELPHI around the graphics topic?

  - by José Eduardo

  Does anyone knows ANY material writen in/for DELPHI around the graphics topic? Planning to build a software for medical imaging processing . Thinking in 3D UI to absorve the power of nvidias GTX graphics card, and some real-time 2D processing integrated with high-end scanners. Please dont take this as a "rant" but, we have zillions of C++ books writen about that kind of topic and nothing for pascal/delphi. If you have some experience could you comment about that? Is it better to learn c++, to have access to that material? Can i go with delphi? I have experience with delphi, but none with graphics... And i have a deadline... Thanks.

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• Method for demonstrating iPad application in online meetings

  - by competent_tech

  We have recently developed an iPad application and now need to start demonstrating it to customers and prospects as part of our overall product suite during webinars. As part of our Agile methodology, we also need to periodically review the application with key customers without having to distribute it since the application is not a standalone application and requires a connection to web services installed at each customer site. We have searched high and low for any solution that doesn't involve rooting the device but have been unable to find one. The most common suggestion seems to be to point a webcam at the device, but that comes across as very unprofessional. I know that there are VGA out adapters that can be plugged into the iPad and we have used these to present through a projector when the customer is physically present, but this is a relatively rare occurrence. Perhaps there are solutions that we are unaware of that can be used to send VGA output back into a desktop device for screen sharing?

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• How can I use multithreading in a Windows Forms application to update a progress bar?

  - by Steve Syfuhs

  There are two objects. The Windows Form with a button and a progress bar, and another object that handles an algorithm. In the algorithm object there is an event, and a property. The event is ProgressChanged, and the property is Progress (which is an int). In the calling window, the button starts off a set of steps in the algorithm object. As each step (or substeps) occurs, the ProgressChanged event fires, and in the window there is an event handler that essentially increments the progress bar relative to the Progress property. The problem I am running into is that because the algorithm has a possibility (and high liklihood) of running a relatively long time, I need to move it into it's own background thread and push the event back up to the window. My issue is that I'm not completely sure what I'm doing when it comes to multi-threading. I've looked at Control.Invoke and I'm a little lost. Can someone point me in the right direction?

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• antlr: How to rewrite only specific

  - by user1293945

  I am sure antlr can solve my problem, but can't figure out how to implement it, even high level. I rapidly got caught into syntax problems of antlr itself. My grammar is quite simple and made of following tokens and rules. Don't really need to go in their details here. The evaluator resolves to expressions, which finally resolve to IDENT: evaluator : expression EOF! ; ... ... term : PARTICIPANT_TYPE(IDENT | '('! expression ')'! | max | min | if_ | NUMBER)+ ; Now, I would like to analyse and rewrite the 'term', so that IDENT tokens (and them only) get re-written with the PARTICIPANT_TYPE. All the others should simply remain the same.

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• Why do so many mathematicians format code so poorly? [closed]

  - by marcog

  I have done a fair amount of programming together with mathematicians. Now I am even teaching some high school kids coming from a mathematics background how to program. Most of these people format their code so hideously it's hard to believe. I've even worked with and taught mathematicians who will fight the auto-indenter! Why is this so common amongst mathematicians? BTW, this is one reason I have started teaching Python. Yet still they find ways other than indentation to produce whacked coding styles!

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• When is a Cocoa callback given controll?

  - by Kaspa

  Hi, I've been searching around the web for an answer to this one, but was unable to find an answer, on the other side I think it's something quite common thus there is a possibility I'm missing some keywords here. Anyhow, the problem is as follows: When is control given to a callback function in ObjC (iPhone)? Does it happen after control is given to a high up in the hierarchy class responsible for the runloop? Can it occur in the middle of another function call being executed? As an example, let's take the NSURLConnection, we don't know or can't predict when it's going to call didReceiveResponse or the other callback methods, can it be the case that didReceiveResponse get's called when I'm in the middle of another function? (highly doubt that but was unable to find information on callbacks wating for the end of the run loop) Cheers, Kaspa

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• Where do I put my php files to have Xampp parse them?

  - by CDeanMartin

  I finished installing Ubuntu 10 for netbooks, and XAMPP. The XAMPP website tutorial made it very easy to install, then left me high and dry. Everything works, but I have no idea where to put my handwritten php files. After a few hours of googling, and trying to understand the file explorer, I realized I have no idea where anything is in ubuntu. For an answer, please don't just tell me "go to "X" directory. I won't know how to navigate there. I also did a file search for htdocs with no luck.

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• How to authorize my app with Facebook

  - by xximjasonxx

  I know I have seen apps that log me in using Facebook but never present me with an authorization screen. I can not, for the life of me, figure out how to do this with Windows Phone 7. The best I have been able to get is using the Facebook for C# SDK to get the authorization screen in a WebView. This looks hideous and the page does not even appear to be mobile ready. I have searched high and low for an answer and have found nothing. Wondering if anyone can point me in the right direction to getting this to work? Thanks in advance

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