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  • Can I prevent a Linux user space pthread yielding in critical code?

    - by KermitG
    I am working on an user space app for an embedded Linux project using the 2.6.24.3 kernel. My app passes data between two file nodes by creating 2 pthreads that each sleep until a asynchronous IO operation completes at which point it wakes and runs a completion handler. The completion handlers need to keep track of how many transfers are pending and maintain a handful of linked lists that one thread will add to and the other will remove. // sleep here until events arrive or time out expires for(;;) { no_of_events = io_getevents(ctx, 1, num_events, events, &timeout); // Process each aio event that has completed or thrown an error for (i=0; i<no_of_events; i++) { // Get pointer to completion handler io_complete = (io_callback_t) events[i].data; // Get pointer to data object iocb = (struct iocb *) events[i].obj; // Call completion handler and pass it the data object io_complete(ctx, iocb, events[i].res, events[i].res2); } } My question is this... Is there a simple way I can prevent the currently active thread from yielding whilst it runs the completion handler rather than going down the mutex/spin lock route? Or failing that can Linux be configured to prevent yielding a pthread when a mutex/spin lock is held?

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  • MySQL replication - Should I handle load balancing from my client code (PHP) ?

    - by pirostraktor
    In a MySQL master-slave replication enviroment if I have 4 slave servers how can I execute load balanced select queries? Should I write a PHP class to dealing with the 4 slaves or it is possible to address queries to MySQL's own load balancer solution? Is there a MySQL load balancing solutions? Can I use some other tool to distribute my queries? What is the typical set up in situations like this? Thanks for all answers!

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  • Would making plain int 64-bit break a lot of reasonable code?

    - by R..
    Until recently, I'd considered the decision by most systems implementors/vendors to keep plain int 32-bit even on 64-bit machines a sort of expedient wart. With modern C99 fixed-size types (int32_t and uint32_t, etc.) the need for there to be a standard integer type of each size 8, 16, 32, and 64 mostly disappears, and it seems like int could just as well be made 64-bit. However, the biggest real consequence of the size of plain int in C comes from the fact that C essentially does not have arithmetic on smaller-than-int types. In particular, if int is larger than 32-bit, the result of any arithmetic on uint32_t values has type signed int, which is rather unsettling. Is this a good reason to keep int permanently fixed at 32-bit on real-world implementations? I'm leaning towards saying yes. It seems to me like there could be a huge class of uses of uint32_t which break when int is larger than 32 bits. Even applying the unary minus or bitwise complement operator becomes dangerous unless you cast back to uint32_t. Of course the same issues apply to uint16_t and uint8_t on current implementations, but everyone seems to be aware of and used to treating them as "smaller-than-int" types.

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  • Speed up math code in C# by writing a C dll?

    - by Projectile Fish
    I have a very large nested for loop in which some multiplications and additions are performed on floating point numbers. for (int i = 0; i < length1; i++) { s = GetS(i); c = GetC(i); for(int j = 0; j < length2; j++) { double oldU = u[j]; u[j] = c * oldU + s * omega[i][j]; omega[i][j] = c * omega[i][j] - s * oldU; } } This loop is taking up the majority of my processing time and is a bottleneck. Would I be likely to see any speed improvements if I rewrite this loop in C and interface to it from C#?

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  • How to fetch populated associated models in CakePHP when calling read()

    - by Code Commander
    I have the following Models: class Site extends AppModel { public $name = "Site"; public $useTable = "site"; public $primaryKey = "id"; public $displayField = 'name'; public $hasMany = array('Item' => array('foreignKey' => 'siteId')); public function canView($userId, $isAdmin = false) { if($isAdmin) { return true; } return array_key_exists($this->id, $allowedSites); } } and class Item extends AppModel { public $name = "Item"; public $useTable = "item"; public $primaryKey = "id"; public $displayField = 'name'; public $belongsTo = array('Site' => array('foreignKey' => 'siteId')); public function canView($userId, $isAdmin = false) { // My problem appears to be the next line: return $this->Site->canView($userId, $isAdmin); } } In my controller I am doing something like this: $result = $this->Item->read(null, $this->request->id); // Verify permissions if(!$this->Item->canView($this->Session->read('userId'), $this->Session->read('isAdmin'))) { $this->httpCodes(403); die('Permission denied.'); } I notice that in Item->canView() $this->data['Site'] is populated with the column data from the site table. But it merely an array and not an object. On the other hand $this->Site is a Site object, but it has not been populated with the column data from the site table like $this->data. What is the proper way to have CakePHP get the associated model as the object and containing the data? Or am I going about this all wrong? Thanks!

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  • Curious: Could LLVM be used for Infocom z-machine code, and if so how? (in general)

    - by jonhendry2
    Forgive me if this is a silly question, but I'm wondering if/how LLVM could be used to obtain a higher performance Z-Machine VM for interactive fiction. (If it could be used, I'm just looking for some high-level ideas or suggestions, not a detailed solution.) It might seem odd to desire higher performance for a circa-1978 technology, but apparently Z-Machine games produced by the modern Inform 7 IDE can have performance issues due to the huge number of rules that need to be evaluated with each turn. Thanks! FYI: The Z-machine architecture was reverse-engineered by Graham Nelson and is documented at http://www.inform-fiction.org/zmachine/standards/z1point0/overview.html

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  • play 3gp videos on windows mobile 5 and 6 from code?

    - by TonyNeallon
    currently im able to play .wmv videos from my application using shell execute which plays it in the windowsmedia player. However I need to be able to play .3gp videos which unfortunately the windows meadia player does not support. Is it possible via api etc to play 3gp videos on win mobile 5 and 6 devices?

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  • MVVM where does the code to load the data belong?

    - by cody
    As I wrap my head around the mvvm thing, the view is the view, and the viewmodel is 'a modal of a view' and the model are the entities we are dealing with (or at least that is my understanding). But I'm unclear as to what and when the model entities are populated. So for example: Lets say I have app that needs to create a new record in a DB. And that record should have default values to start with. Who is responsible for the new record, and getting the default values. Does this have anything to do with MVVM or is that part of a data access layer? Who calls the the viewmodel? Or for existing records when\where are the records retrieved? And saved if altered? Thanks

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  • UNIX script to parse Zone file (is this the best code?)

    - by Steve
    Hi, FOund the following on: http://mike.murraynet.net/2009/08/23/parsing-the-verisign-zone-file-with-os-x/ Can unix-masters have a look at it and see if its the best possible way to gather the unique domainsnames in a zone file? For .NET domains: grep “^[a-zA-Z0-9-]+ NS .” net.zone|sed “s/NS .//”|uniq netdomains.txt For .COM domains: grep “^[a-zA-Z0-9-]+ NS .” com.zone|sed “s/NS .//”|uniq comdomains.txt For .EDU domains: grep “^[a-zA-Z0-9-]+ NS .” edu.zone|sed “s/NS .//”|uniq edudomains.txt

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  • File streaming in PHP - How to replicate this C#.net code in PHP?

    - by openid_kenja
    I'm writing an interface to a web service where we need to upload configuration files. The documentation only provides a sample in C#.net which I am not familiar with. I'm trying to implement this in PHP. Can someone familiar with both languages point me in the right direction? I can figure out all the basics, but I'm trying to figure out suitable PHP replacements for the FileStream, ReadBytes, and UploadDataFile functions. I believe that the RecService object contains the URL for the web service. Thanks for your help! private void UploadFiles() { clientAlias = “<yourClientAlias>”; string filePath = “<pathToYourDataFiles>”; string[] fileList = {"Config.txt", "ProductDetails.txt", "BrandNames.txt", "CategoryNames.txt", "ProductsSoldOut.txt", "Sales.txt"}; RecommendClient RecService = new RecommendClient(); for (int i = 0; i < fileList.Length; i++) { bool lastFile = (i == fileList.Length - 1); //start generator after last file try { string fileName = filePath + fileList[i]; if (!File.Exists(fileName)) continue; // file not found } // set up a file stream and binary reader for the selected file and convert to byte array FileStream fStream = new FileStream(fileName, FileMode.Open, FileAccess.Read); BinaryReader br = new BinaryReader(fStream); byte[] data = br.ReadBytes((int)numBytes); br.Close(); // pass byte array to the web service string result = RecService.UploadDataFile(clientAlias, fileList[i], data, lastFile); fStream.Close(); fStream.Dispose(); } catch (Exception ex) { // log an error message } } }

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  • Why is PLINQ slower than LINQ for this code?

    - by Rob Packwood
    First off, I am running this on a dual core 2.66Ghz processor machine. I am not sure if I have the .AsParallel() call in the correct spot. I tried it directly on the range variable too and that was still slower. I don't understand why... Here are my results: Process non-parallel 1000 took 146 milliseconds Process parallel 1000 took 156 milliseconds Process non-parallel 5000 took 5187 milliseconds Process parallel 5000 took 5300 milliseconds using System; using System.Collections.Generic; using System.Diagnostics; using System.Linq; namespace DemoConsoleApp { internal class Program { private static void Main() { ReportOnTimedProcess( () => GetIntegerCombinations(), "non-parallel 1000"); ReportOnTimedProcess( () => GetIntegerCombinations(runAsParallel: true), "parallel 1000"); ReportOnTimedProcess( () => GetIntegerCombinations(5000), "non-parallel 5000"); ReportOnTimedProcess( () => GetIntegerCombinations(5000, true), "parallel 5000"); Console.Read(); } private static List<Tuple<int, int>> GetIntegerCombinations( int iterationCount = 1000, bool runAsParallel = false) { IEnumerable<int> range = Enumerable.Range(1, iterationCount); IEnumerable<Tuple<int, int>> integerCombinations = from x in range from y in range select new Tuple<int, int>(x, y); return runAsParallel ? integerCombinations.AsParallel().ToList() : integerCombinations.ToList(); } private static void ReportOnTimedProcess( Action process, string processName) { var stopwatch = new Stopwatch(); stopwatch.Start(); process(); stopwatch.Stop(); Console.WriteLine("Process {0} took {1} milliseconds", processName, stopwatch.ElapsedMilliseconds); } } }

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  • MSSQL: Primary Key Schema Largely Guid but Sometimes Integer Types...

    - by Code Sherpa
    OK, this may be a silly question but... I have inherited a project and am tasked with going over the primary key relationships. The project largely uses Guids. I say "largely" because there are examples where tables use integral types to reflect enumerations. For example, dbo.MessageFolder has MessageFolderId of type int to reflect public emum MessageFolderTypes { inbox = 1, sent = 2, trash = 3, etc... } This happens a lot. There are tables with primary keys of type int which is unavoidable because of their reliance on enumerations and tables with primary keys of type Guid which reflect the primary key choice on the part of the previous programmer. Should I care that the PK schema is spotty like this? It doesn't feel right but does it really matter? If this could create a problem, how do I get around it (I really can't move all PKs to type int without serious legwork and I have never heard of enumerations that have guid values)? Thanks.

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  • How can I write cocoa bindings as code instead of in the Interface Builder?

    - by johnjohndoe
    In my modell got an NSMutableArray that keeps track of a changing number of elements. In my view I got a NSTextField that shows the number of elements. The view gots unarchived from the nib file and alloc/inits the modell. Therefore it knowns about the modell and the contained array. I established the connection as follows. In the Interface Builder at the textfield I added a Cocoa Binding "path" like this: myModell.myArray.@count. By this I can access the count property (which is a must since the array itself does not change). The binding is based on key-value compliance which I established at the modell so the array can be accessed. But key-value compliance is not part of the questions. My question: How can I put the binding into the sourcecode and not writing it into the Interface Builder?

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  • Why do I get HTTP Code 414 on one network but not another?

    - by Stephen Darlington
    I have an otherwise working iPhone program. A recent change means that it generates some very long URLs (over 4000 characters sometimes) which I know isn't a great idea and I know how to fix -- that's not what I'm asking here. The curious thing is that when I make the connection using a 3G network (Vodafone UK) I get this HTTP "414 Request-URI Too Long" error but when I connect using my local WiFi connection it works just fine. Why would I get different results using different types of network? Could they be routing requests to different servers depending on where the connection originates? Or is there something else at stake here? The corollary questions relate to how common this is. Is it likely to happen whenever I use a cell network or just some networks?

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  • Why in the following code the output is different when I compile or run it more than once

    - by Sanjeev
    class Name implements Runnable { public void run() { for (int x = 1; x <= 3; x++) { System.out.println("Run by " + Thread.currentThread().getName() + ", x is " + x); } } } public class Threadtest { public static void main(String [] args) { // Make one Runnable Name nr = new Name(); Thread one = new Thread(nr); Thread two = new Thread(nr); Thread three = new Thread(nr); one.setName("A"); two.setName("B"); three.setName("C"); one.start(); two.start(); three.start(); } } The answer is different while compiling and running more then one time I don't know why? any idea.

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