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• Foreach PHP Error

  - by Logan

  I am receiving the following foreach error on my PHP file and I have no idea how to fix it. Does anyone have any ideas? When I load the page I get this: Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 61 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/merge/class/global_functions.php on line 89 Line 61 and 89 of my /class/global_functions.php are as followed: Here is my code from line 61 to line 98: foreach($GLOBALS['userpermbit'] as $v) { if(strstr($v['perm'],'|'.$pageperm_id[0]['id'].'|')) return true; } //if they dont have perms and we're not externally including functions return false if ($GLOBALS['external'] != true) return false; return true; } //FUNCTION: quick perm check using perm info from the onload perm check function stealthPermCheck($req) { #if theyre an admin give them perms if(@in_array($GLOBALS['user'][0]['id'], $GLOBALS['superAdmins'])) return true; if(!is_numeric($req)) { #if the req is numeric we need to match a title, not a permid. So try to do that foreach($GLOBALS['userpermbit'] as $v) { if(stristr($v['title'],$req)) return true; } }else{ #check if they have perms numerically if so return true foreach($GLOBALS['userpermbit'] as $v) { if(strstr($v['perm'],'|'.$req.'|')) return true; } } #if none of this returned true they dont have perms, return false return false; }

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• Overflow exception while performing parallel factorization using the .NET Task Parallel Library (TPL

  - by Aviad P.

  Hello, I'm trying to write a not so smart factorization program and trying to do it in parallel using TPL. However, after about 15 minutes of running on a core 2 duo machine, I am getting an aggregate exception with an overflow exception inside it. All the entries in the stack trace are part of the .NET framework, the overflow does not come from my code. Any help would be appreciated in figuring out why this happens. Here's the commented code, hopefully it's simple enough to understand: class Program { static List<Tuple<BigInteger, int>> factors = new List<Tuple<BigInteger, int>>(); static void Main(string[] args) { BigInteger theNumber = BigInteger.Parse( "653872562986528347561038675107510176501827650178351386656875178" + "568165317809518359617865178659815012571026531984659218451608845" + "719856107834513527"); Stopwatch sw = new Stopwatch(); bool isComposite = false; sw.Start(); do { /* Print out the number we are currently working on. */ Console.WriteLine(theNumber); /* Find a factor, stop when at least one is found (using the Any operator). */ isComposite = Range(theNumber) .AsParallel() .Any(x => CheckAndStoreFactor(theNumber, x)); /* Of the factors found, take the one with the lowest base. */ var factor = factors.OrderBy(x => x.Item1).First(); Console.WriteLine(factor); /* Divide the number by the factor. */ theNumber = BigInteger.Divide( theNumber, BigInteger.Pow(factor.Item1, factor.Item2)); /* Clear the discovered factors cache, and keep looking. */ factors.Clear(); } while (isComposite); sw.Stop(); Console.WriteLine(isComposite + " " + sw.Elapsed); } static IEnumerable<BigInteger> Range(BigInteger squareOfTarget) { BigInteger two = BigInteger.Parse("2"); BigInteger element = BigInteger.Parse("3"); while (element * element < squareOfTarget) { yield return element; element = BigInteger.Add(element, two); } } static bool CheckAndStoreFactor(BigInteger candidate, BigInteger factor) { BigInteger remainder, dividend = candidate; int exponent = 0; do { dividend = BigInteger.DivRem(dividend, factor, out remainder); if (remainder.IsZero) { exponent++; } } while (remainder.IsZero); if (exponent > 0) { lock (factors) { factors.Add(Tuple.Create(factor, exponent)); } } return exponent > 0; } } Here's the exception thrown: Unhandled Exception: System.AggregateException: One or more errors occurred. --- > System.OverflowException: Arithmetic operation resulted in an overflow. at System.Linq.Parallel.PartitionedDataSource`1.ContiguousChunkLazyEnumerator.MoveNext(T& currentElement, Int32& currentKey) at System.Linq.Parallel.AnyAllSearchOperator`1.AnyAllSearchOperatorEnumerator`1.MoveNext(Boolean& currentElement, Int32& currentKey) at System.Linq.Parallel.StopAndGoSpoolingTask`2.SpoolingWork() at System.Linq.Parallel.SpoolingTaskBase.Work() at System.Linq.Parallel.QueryTask.BaseWork(Object unused) at System.Linq.Parallel.QueryTask.<.cctor>b__0(Object o) at System.Threading.Tasks.Task.InnerInvoke() at System.Threading.Tasks.Task.Execute() --- End of inner exception stack trace --- at System.Linq.Parallel.QueryTaskGroupState.QueryEnd(Boolean userInitiatedDispose) at System.Linq.Parallel.SpoolingTask.SpoolStopAndGo[TInputOutput,TIgnoreKey](QueryTaskGroupState groupState, PartitionedStream`2 partitions, SynchronousChannel`1[] channels, TaskScheduler taskScheduler) at System.Linq.Parallel.DefaultMergeHelper`2.System.Linq.Parallel.IMergeHelper<TInputOutput>.Execute() at System.Linq.Parallel.MergeExecutor`1.Execute[TKey](PartitionedStream`2 partitions, Boolean ignoreOutput, ParallelMergeOptions options, TaskScheduler taskScheduler, Boolean isOrdered, CancellationState cancellationState, Int32 queryId) at System.Linq.Parallel.PartitionedStreamMerger`1.Receive[TKey](PartitionedStream`2 partitionedStream) at System.Linq.Parallel.AnyAllSearchOperator`1.WrapPartitionedStream[TKey](PartitionedStream`2 inputStream, IPartitionedStreamRecipient`1 recipient, BooleanpreferStriping, QuerySettings settings) at System.Linq.Parallel.UnaryQueryOperator`2.UnaryQueryOperatorResults.ChildResultsRecipient.Receive[TKey](PartitionedStream`2 inputStream) at System.Linq.Parallel.ScanQueryOperator`1.ScanEnumerableQueryOperatorResults.GivePartitionedStream(IPartitionedStreamRecipient`1 recipient) at System.Linq.Parallel.UnaryQueryOperator`2.UnaryQueryOperatorResults.GivePartitionedStream(IPartitionedStreamRecipient`1 recipient) at System.Linq.Parallel.QueryOperator`1.GetOpenedEnumerator(Nullable`1 mergeOptions, Boolean suppressOrder, Boolean forEffect, QuerySettings querySettings) at System.Linq.Parallel.QueryOpeningEnumerator`1.OpenQuery() at System.Linq.Parallel.QueryOpeningEnumerator`1.MoveNext() at System.Linq.Parallel.AnyAllSearchOperator`1.Aggregate() at System.Linq.ParallelEnumerable.Any[TSource](ParallelQuery`1 source, Func`2 predicate) at PFact.Program.Main(String[] args) in d:\myprojects\PFact\PFact\Program.cs:line 34 Any help would be appreciated. Thanks!

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• JVM (embarrasingly) parallel processing libraries/tools

  - by Winterstream

  I am looking for something that will make it easy to run (correctly coded) embarrassingly parallel JVM code on a cluster (so that I can use Clojure + Incanter). I have used Parallel Python in the past to do this. We have a new PBS cluster and our admin will soon set up IPython nodes that use PBS as the backend. Both of these systems make it almost a no-brainer to run certain types of code in a cluster. I made the mistake of using Hadoop in the past (Hadoop is just not suited to the kind of data that I use) - the latency made even small runs execute for 1-2 minutes. Is JPPF or Gridgain better for what I need? Does anyone here have any experience with either? Is there anything else you can recommend?

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• 'foreach' failing when using Parallel Task Library

  - by Chris Arnold

  The following code creates the correct number of files, but every file contains the contents of the first list. Can anyone spot what I've done wrong please? private IList<List<string>> GetLists() { // Code omitted for brevity... } private void DoSomethingInParallel() { var lists = GetLists(); var tasks = new List<Task>(); var factory = new TaskFactory(); foreach (var list in lists) { tasks.Add(factory.StartNew(() => { WriteListToLogFile(list); })); } Task.WaitAll(tasks.ToArray()); }

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• Evaluating a function at a particular value in parallel

  - by Gaurav Kalra

  Hi. The question may seem vague, but let me explain it. Suppose we have a function f(x,y,z ....) and we need to find its value at the point (x1,y1,z1 .....). The most trivial approach is to just replace (x,y,z ...) with (x1,y1,z1 .....). Now suppose that the function is taking a lot of time in evaluation and I want to parallelize the algorithm to evaluate it. Obviously it will depend on the nature of function, too. So my question is: what are the constraints that I have to look for while "thinking" to parallelize f(x,y,z...)? If possible, please share links to study.

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• PHP - Foreach in a foreach + CodeIgniter

  - by Sebhael

  I got an image upload function working, but there's 4 images required in this image. And my current function is simply just overwriting the image despite the number. I'm wondering how I would insert (preferably) a letter into my foreach function. $uploads = array($this->uploads->data()); foreach ( $uploads as $key[] => $value ) { $imagename = $cleaned . '-s' . $value['file_ext']; //outputs clean-name-s.ext } By the time all is said and done, 4 images will require this function. Leaving me with clean-name-sa.ext, clean-name-sb.ext, clean-name-sc.ext, and clean-name-sd.ext (numbers work as well). The form does require that all 4 fields are filled out before submission, so would I just create an array of my desired identifiers and create a foreach loop that outputs 4 different $imagenames? Or is there a simpler, more logical approach to this.

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• Help with converting foreach loop to while loop in c#

  - by James Dawson

  I had learnt by reading your great answers here, that it is not good practice deleting items from within a foreach loop, as it is (and I quote) "Sawing off the branch you're sitting on". My code currently removes the text from the dropdownlist, but the actual item remains (just without text displayed). In other words, it isn't deleting, and probably can't because you can't delete from within a foreach loop. After hours of trying I am unable to get my head around a way of doing it. //For each checked box, run the delete code for (int i = 0; i < this.organizeFav.CheckedItems.Count; i++) { //this is the foreach loop foreach (ToolStripItem mItem in favoritesToolStripMenuItem.DropDownItems) { //This rules out seperators if (mItem is ToolStripMenuItem) { ToolStripMenuItem menuItem = mItem as ToolStripMenuItem; //This matches the dropdownitems text to the CheckedItems String if (((ToolStripMenuItem)mItem).Text.ToString() == organizeFav.CheckedItems[i].ToString()) { //And deletes the item menuItem.DropDownItems.Remove(mItem); } } } } But it isn't deleting because it is within a foreach loop! I would greatly appreciate your help, and be truly amazed if anyone can get their head around this code :) Kind Regards

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• Parallel MSBuild FTW - Build faster in parallel

  - by deadlydog

  Hey everyone, I just discovered this great post yesterday that shows how to have msbuild build projects in parallel Basically all you need to do is pass the switches “/m:[NumOfCPUsToUse] /p:BuildInParallel=true” into MSBuild. Example to use 4 cores/processes (If you just pass in “/m” it will use all CPU cores): MSBuild /m:4 /p:BuildInParallel=true "C:\dev\Client.sln" Obviously this trick will only be useful on PCs with multi-core CPUs (which we should all have by now) and solutions with multiple projects; So there’s no point using it for solutions that only contain one project.  Also, testing shows that using multiple processes does not speed up Team Foundation Database deployments either in case you’re curious Also, I found that if I didn’t explicitly use “/p:BuildInParallel=true” I would get many build errors (even though the MSDN documentation says that it is true by default). The poster boasts compile time improvements up to 59%, but the performance boost you see will vary depending on the solution and its project dependencies.  I tested with building a solution at my office, and here are my results (runs are in seconds): # of Processes 1st Run 2nd Run 3rd Run Avg Performance 1 192 195 200 195.67 100% 2 155 156 156 155.67 79.56% 4 146 149 146 147.00 75.13% 8 136 136 138 136.67 69.85%   So I updated all of our build scripts to build using 2 cores (~20% speed boost), since that gives us the biggest bang for our buck on our solution without bogging down a machine, and developers may sometimes compile more than 1 solution at a time.  I’ve put the any-PC-safe batch script code at the bottom of this post. The poster also has a follow-up post showing how to add a button and keyboard shortcut to the Visual Studio IDE to have VS build in parallel as well (so you don’t have to use a build script); if you do this make sure you use the .Net 4.0 MSBuild, not the 3.5 one that he shows in the screenshot.  While this did work for me, I found it left an MSBuild.exe process always hanging around afterwards for some reason, so watch out (batch file doesn’t have this problem though).  Also, you do get build output, but it may not be the same that you’re used to, and it doesn’t say “Build succeeded” in the status bar when completed, so I chose to not make this my default Visual Studio build option, but you may still want to. Happy building! ------------------------------------------------------------------------------------- :: Calculate how many Processes to use to do the build. SET NumberOfProcessesToUseForBuild=1  SET BuildInParallel=false if %NUMBER_OF_PROCESSORS% GTR 2 (                 SET NumberOfProcessesToUseForBuild=2                 SET BuildInParallel=true ) MSBuild /maxcpucount:%NumberOfProcessesToUseForBuild% /p:BuildInParallel=%BuildInParallel% "C:\dev\Client.sln"

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• Parallel Debugging

  Using Visual Studio 2010 parallel debugging is easy. Two new debugging windows provide a total view of the internals of your PPL and TPL applications with hints on where to start investigations. These are not mere extensions to VS, but tightly integrated with the rest of the debugger experience, so you don't need to learn many new techniques. Use them in your program to eclipse bugs from existence!One of the most FAQ I receive is links to VS2010 parallel debugging content and rather than keep sending many, I decided to gather them all under one permalink, hence this multi link blog post.- MSDN Magazine article on Parallel Debugging.- Screencast of sample code from the article.- MSDN Walkthrough: Debugging a Parallel Application (VB, C++, C#).- Screencast of walkthrough for Parallel Stacks.- Screencast of walkthrough for Parallel Tasks.- MSDN "How To" on Parallel Tasks.- MSDN "How To" on Parallel Stacks.- Detailed blog post on Parallel Tasks.- Detailed blog post on Parallel Stacks.- Detailed blog post on Parallel Stacks - Tasks View.- Detailed blog post on Parallel Stacks - Method View.- Download slides on Parallel Tasks and Parallel Stacks (pptx).If you have questions on these, please post to any of the parallel computing forums or the debugging forum (your question will be routed to me if nobody else can answer it). Comments about this post welcome at the original blog.

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• What is massively parallel processing (MPP) ?

  - by HotTester

  Ever since Microsoft introduced sql-server version code-named "Madison" the massively parallel processing (MPP) has got into picture. What exactly is it and how does sql-server is going to benefit from it ? Further is massively parallel processing (MPP) related to parallel computing ? I read about Madison here and about parallel computing here. Thanks in advance.

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• Bash script 'while read' loop causes 'broken pipe' error when run with GNU Parallel

  - by Joe White

  According to the GNU Parallel mailing list this is not a GNU Parallel-specific problem. They suggested that I post my problem here. The error I'm getting is a "broken pipe" error, but I feel I should first explain the context of my problem and what causes this error. It happens when trying to use any bash script containing a 'while read' loop in GNU Parallel. I have a basic bash script like this: #!/bin/bash # linkcheck.sh while read domain do host "$domain" done Assume that I want to pipe in a large list (250mb say). cat urllist | ./linkcheck.sh Running host command on 250mb worth of URLs is rather slow. To speed things up I want to break up the input into chunks before piping it and then run multiple jobs in parallel. GNU Parallel is capable of doing this. cat urllist | parallel --pipe -j0 parallel ./linkcheck.sh {} {} is substituted by the contents of urllist line-by-line. Assume that my systems default setup is capable of running 500ish jobs per instance of parallel. To get round this limitation we can parallelize Parallel itself: cat urllist | parallel -j10 --pipe parallel -j0 ./linkcheck.sh {} This will run 5000'ish jobs. It will also, sadly, cause the error "broken pipe" (bash FAQ). Yet the script starts to work if I remove the while read loop and take input directly from whatever is fed into {} e.g., #!/bin/bash # linkchecker.sh domain="$1" host "$1" Why will it not work with a while read loop? Is it safe to just turn off the SIGPIPE signal to stop the "broken pipe" message, or will that have side effects such as data corruption? Thanks for reading.

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• Parallel.For Inconsistency results

  - by ni Gue ???

  I am using VB.net to write a parallel based code. I use Parallel.For to generate pairs of 500 objects or in combination C(500,2) such as the following code; but I found that it didn't always generate all combinations which should be 124750 (shown from variable Counter). No other thread was runing when this code was run. I am using a Win-7 32 Bit desktop with Intel Core i5 CPU [email protected], 3.33 GHz and RAM 2GB. What's wrong with the code and how to solve this problem? Thank You. Dim Counter As Integer = 0 Parallel.For(0, 499, Sub(i) For j As Integer = i + 1 To 499 Counter += 1 Console.Write(i & ":" & j) Next End Sub) Console.Writeline("Iteration number: " & Counter)

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• LinqToSql - Parallel - DataContext and Parallel

  - by Gregoire

  In .NET 4 and multicore environment, does the linq to sql datacontext object take advantage of the new parallels if we use DataLoadOptions.LoadWith? EDIT I know linq to sql does not parallelize ordinary queries. What I want to know is when we specify DataLoadOption.LoadWith, does it use parallelization to perform the match between each entity and its sub entities? Example: using(MyDataContext context = new MyDataContext()) { DataLaodOptions options =new DataLoadOptions(); options.LoadWith<Product>(p=>p.Category); return this.DataContext.Products.Where(p=>p.SomeCondition); } generates the following sql: Select Id,Name from Categories Select Id,Name, CategoryId from Products where p.SomeCondition when all the products are created, will we have a categories.ToArray(); Parallel.Foreach(products, p => { p.Category == categories.FirstOrDefault(c => c.Id == p.CategoryId); }); or categories.ToArray(); foreach(Product product in products) { product.Category = categories.FirstOrDefault(c => c.Id == product.CategoryId); } ?

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• Going Parallel with the Task Parallel Library and PLINQ

  With more and more computers using a multi-core processor, the free lunch of increased clock speeds and the inherent performance gains are over. Software developers must instead make sure their applications take use of all the cores available in an efficient manner. New features in .NET 4.0 mean that managed code developers too can join the party.

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• Studying parallel programming

  - by mort

  I'm currently finishing my Bachelor's degree in Computer Science and thinking a lot about which specialisation to choose in my Master's degree. One subject I'm particularly interested in is parallel programming. However, this topic does not seem to be a standard topic in Computer Science degrees, although it is something that is used more and more - new processors nowadays are usually dual or quad cores. So I was wandering: does anybody know a good study program in this field? I was mostly looking for it at universities in Germany, but they tend to combine the application side with some type of engineering or natural science. Thus, programs are more the "Computational Engineering" or "Computational Science" type, but I'm more interested in the Computer Science part of it, i.e. parallel programming, languages and compilers, algorithms and hardware.

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• printing parallel over ethernet cable

  - by Crudler

  I have a bit of an interesting challenge :) I have a machine with a parallel printer output, i want it to be able to print instead to a printer in a different room and i know that parallel isnt great over big distances. i found this: http://www.amazon.com/over-Cat5-Extension-Cable-Adapter/dp/B002WJ9S6Y%3FSubscriptionId%3DAKIAINHICTCYYZGJWT4Q%26tag%3Dusbprintercables.net-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D165953%26creativeASIN%3DB002WJ9S6Y which will let me connect over cat5, but its usb to cat 5. my machine can only output on parallel (its not a computer) so what i was thinking of getting is a parallel(f) to usb and usb to parallel (M) for either side i.e. machine - parallel - usb - cat5 - usb - parallel -printer just seems a bit messy :) suggestions? another thing i would like to try is to get rid of the old school parallel printer and instead use a network based multi function. would this be possible? i.e. machine - parallel -usb - cat5 - ethernet print server - network printer this might be rougher because the machine cannot "know" that we are using a network printer. it can ONLY print to LPT1 Thanks!

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• Which parallel pattern to use?

  - by Wim Van Houts

  I need to write a server application that fetches mails from different mail servers/mailboxes and then needs to process/analyze these mails. Traditionally, I would do this multi-threaded, launching a thread for fetching mails (or maybe one per mailbox) and then process the mails. We are moving more and more to servers where we have 8+ cores, so I would like to make use of these cores as much as possible (and not use 1 at 100% and leave the seven others untouched). So conceptually, as an example, it would be nice that I could write the application in such a way that two cores are "continuously" fetching emails and four cores are "continuously" processing/analyzing the emails (since processing and analyzing mails is more CPU intensive than fetching mails). This seems like a good concept, but after studying some parallel patterns, I'm not really sure how this is best implemented. None of the patterns really fit. I'm working in VS2012, native C++, but I guess from a design point of view this does not really matter and just some pointers on how to organize this would be great!

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• Java Parallel Programming

  - by user578524

  Dear All, I need to parallelize a CPU intensive Java application on my multicore desktop but I am not so comfortable with threads programming. I looked at Scala but this would imply learning a new language which is really time consuming. I also looked at Ateji PX Java parallel extensions which seem very easy to use but did not have a chance yet to evaluate it. Would anyone recommend it? Other suggestions welcome. Thanks in advance for your help Bill

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• Embarrassingly parallel workflow creates too many output files

  - by Hooked

  On a Linux cluster I run many (N > 10^6) independent computations. Each computation takes only a few minutes and the output is a handful of lines. When N was small I was able to store each result in a separate file to be parsed later. With large N however, I find that I am wasting storage space (for the file creation) and simple commands like ls require extra care due to internal limits of bash: -bash: /bin/ls: Argument list too long. Each computation is required to run through a qsub scheduling algorithm so I am unable to create a master program which simply aggregates the output data to a single file. The simple solution of appending to a single fails when two programs finish at the same time and interleave their output. I have no admin access to the cluster, so installing a system-wide database is not an option. How can I collate the output data from embarrassingly parallel computation before it gets unmanageable?

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• C# - foreach showing strange behavior / for working with no problem

  - by Marks

  Hi there. Today I coded a function that uses two nested foreach loops. After seeing, that it did not work like expected, i debugged it. But I dont see an error, and dont think a simple error can cause the behavior i have noticed. The part looks like this: foreach(MyClass cItem in checkedListBoxItemList.Items) { foreach(MyClass cActiveItem in ActiveItemList) { if (cActiveItem.ID == cItem.ID) /*...check checkbox for item...*/; } } Lets say, checkedListBoxItemList.items holds 4 items of type MyClass, and ActiveItemList is a List< MyClass with 2 Items. The debugger jumps into the outer foreach, reaches inner foreach, executes the if 2 times (once per cActiveItem) and reaches the end of the outer foreach.Now, the debugger jumps back to the head of the outer foreach as it should. But instead of starting the second round of the outer foreach, the debugger suddenly jumps into the MyClass.ToString() method. I can step through this method 4 times (number of items in checkedListBoxItemList.Items) and then ... nothing. Visual Studio shows me my windows form, and the foreach is not continued. When changing the code to int ListCount = checkedListBoxItemList.Items.Count; for(int i=0; i<ListCount; i++) { MyClass cItem = checkedListBoxItemList.Items[i] as MyClass; foreach(MyClass cActiveItem in ActiveItemList) { if (cActiveItem.ID == cItem.ID) /*...check checkbox for item...*/; } } everything works fine and as supposed. I showed the problem to a collegue, but he also didnt understand, what happened. I dont understand why the debugger jumps into the MyClass.ToString() method. I used F10 to step through, so no need to leave the function. And even, if there is a reason, why isnt the foreach loop continued? Im using Visual Studio 2010, if this is of any matter. Please tell me what happened. Thanks.

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• Parallel processing via multithreading in Java

  - by Robz

  There are certain algorithms whose running time can decrease significantly when one divides up a task and gets each part done in parallel. One of these algorithms is merge sort, where a list is divided into infinitesimally smaller parts and then recombined in a sorted order. I decided to do an experiment to test whether or not I could I increase the speed of this sort by using multiple threads. I am running the following functions in Java on a Quad-Core Dell with Windows Vista. One function (the control case) is simply recursive: // x is an array of N elements in random order public int[] mergeSort(int[] x) { if (x.length == 1) return x; // Dividing the array in half int[] a = new int[x.length/2]; int[] b = new int[x.length/2+((x.length%2 == 1)?1:0)]; for(int i = 0; i < x.length/2; i++) a[i] = x[i]; for(int i = 0; i < x.length/2+((x.length%2 == 1)?1:0); i++) b[i] = x[i+x.length/2]; // Sending them off to continue being divided mergeSort(a); mergeSort(b); // Recombining the two arrays int ia = 0, ib = 0, i = 0; while(ia != a.length || ib != b.length) { if (ia == a.length) { x[i] = b[ib]; ib++; } else if (ib == b.length) { x[i] = a[ia]; ia++; } else if (a[ia] < b[ib]) { x[i] = a[ia]; ia++; } else { x[i] = b[ib]; ib++; } i++; } return x; } The other is in the 'run' function of a class that extends thread, and recursively creates two new threads each time it is called: public class Merger extends Thread { int[] x; boolean finished; public Merger(int[] x) { this.x = x; } public void run() { if (x.length == 1) { finished = true; return; } // Divide the array in half int[] a = new int[x.length/2]; int[] b = new int[x.length/2+((x.length%2 == 1)?1:0)]; for(int i = 0; i < x.length/2; i++) a[i] = x[i]; for(int i = 0; i < x.length/2+((x.length%2 == 1)?1:0); i++) b[i] = x[i+x.length/2]; // Begin two threads to continue to divide the array Merger ma = new Merger(a); ma.run(); Merger mb = new Merger(b); mb.run(); // Wait for the two other threads to finish while(!ma.finished || !mb.finished) ; // Recombine the two arrays int ia = 0, ib = 0, i = 0; while(ia != a.length || ib != b.length) { if (ia == a.length) { x[i] = b[ib]; ib++; } else if (ib == b.length) { x[i] = a[ia]; ia++; } else if (a[ia] < b[ib]) { x[i] = a[ia]; ia++; } else { x[i] = b[ib]; ib++; } i++; } finished = true; } } It turns out that function that does not use multithreading actually runs faster. Why? Does the operating system and the java virtual machine not "communicate" effectively enough to place the different threads on different cores? Or am I missing something obvious?

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• C# 4.0 'dynamic' and foreach statement

  - by ControlFlow

  Not long time before I've discovered, that new dynamic keyword doesn't work well with the C#'s foreach statement: using System; sealed class Foo { public struct FooEnumerator { int value; public bool MoveNext() { return true; } public int Current { get { return value++; } } } public FooEnumerator GetEnumerator() { return new FooEnumerator(); } static void Main() { foreach (int x in new Foo()) { Console.WriteLine(x); if (x >= 100) break; } foreach (int x in (dynamic)new Foo()) { // :) Console.WriteLine(x); if (x >= 100) break; } } } I've expected that iterating over the dynamic variable should work completely as if the type of collection variable is known at compile time. I've discovered that the second loop actually is looked like this when is compiled: foreach (object x in (IEnumerable) /* dynamic cast */ (object) new Foo()) { ... } and every access to the x variable results with the dynamic lookup/cast so C# ignores that I've specify the correct x's type in the foreach statement - that was a bit surprising for me... And also, C# compiler completely ignores that collection from dynamically typed variable may implements IEnumerable<T> interface! The full foreach statement behavior is described in the C# 4.0 specification 8.8.4 The foreach statement article. But... It's perfectly possible to implement the same behavior at runtime! It's possible to add an extra CSharpBinderFlags.ForEachCast flag, correct the emmited code to looks like: foreach (int x in (IEnumerable<int>) /* dynamic cast with the CSharpBinderFlags.ForEachCast flag */ (object) new Foo()) { ... } And add some extra logic to CSharpConvertBinder: Wrap IEnumerable collections and IEnumerator's to IEnumerable<T>/IEnumerator<T>. Wrap collections doesn't implementing Ienumerable<T>/IEnumerator<T> to implement this interfaces. So today foreach statement iterates over dynamic completely different from iterating over statically known collection variable and completely ignores the type information, specified by user. All that results with the different iteration behavior (IEnumarble<T>-implementing collections is being iterated as only IEnumerable-implementing) and more than 150x slowdown when iterating over dynamic. Simple fix will results a much better performance: foreach (int x in (IEnumerable<int>) dynamicVariable) { But why I should write code like this? It's very nicely to see that sometimes C# 4.0 dynamic works completely the same if the type will be known at compile-time, but it's very sadly to see that dynamic works completely different where IT CAN works the same as statically typed code. So my question is: why foreach over dynamic works different from foreach over anything else?

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• Async.Parallel or Array.Parallel.Map ?

  - by gurteen2

  Hello- I'm trying to implement a pattern I read from Don Syme's blog (http://blogs.msdn.com/dsyme/archive/2010/01/09/async-and-parallel-design-patterns-in-f-parallelizing-cpu-and-i-o-computations.aspx) which suggests that there are opportunities for massive performance improvements from leveraging asynchronous I/O. I am currently trying to take a piece of code that "works" one way, using Array.Parallel.Map, and see if I can somehow achieve the same result using Async.Parallel, but I really don't understand Async.Parallel, and cannot get anything to work. I have a piece of code (simplified below to illustrate the point) that successfully retrieves an array of data for one cusip. (A price series, for example) let getStockData cusip = let D = DataProvider() let arr = D.GetPriceSeries(cusip) return arr let data = Array.Parallel.map (fun x -> getStockData x) stockCusips So this approach contructs an array of arrays, by making a connection over the internet to my data vendor for each stock (which could be as many as 3000) and returns me an array of arrays (1 per stock, with a price series for each one). I admittedly don't understand what goes on underneath Array.Parallel.map, but am wondering if this is a scenario where there are resources wasted under the hood, and it actually could be faster using asynchronous I/O? So to test this out, I have attempted to make this function using asyncs, and I think that the function below follows the pattern in Don Syme's article using the URLs, but it won't compile with "let!". let getStockDataAsync cusip = async { let D = DataProvider() let! arr = D.GetData(cusip) return arr } The error I get is: This expression was expected to have type Async<'a but here has type obj It compiles fine with "let" instead of "let!", but I had thought the whole point was that you need the exclamation point in order for the command to run without blocking a thread. So the first question really is, what's wrong with my syntax above, in getStockDataAsync, and then at a higher level, can anyone offer some additional insight about asychronous I/O and whether the scenario I have presented would benefit from it, making it potentially much, much faster than Array.Parallel.map? Thanks so much.

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• Parallel Desktops: installing Parallel Tools on Ubuntu

  - by Patrick

  hi, I get the following error when I try to install Parallel Tools on my Ubuntu in Parallel Desktop. I follow the istructions, running sh install from terminal: I follow the UI istructions and then the installation stops with this error message: E: Couldn't find package dkms Fri May 7 14:34:20 PDT 2010 Start installation or upgrade of Guest Tools Installed Guest Tools were not found Perform installation into the /usr/lib/parallels-tools directory cat: /usr/lib/parallels-tools/kmods/../version: No such file or directory Start installation of prl_eth kernel module make: Entering directory `/usr/lib/parallels-tools/kmods' cd prl_eth/pvmnet && make make[1]: Entering directory `/usr/lib/parallels-tools/kmods/prl_eth/pvmnet' make -C /lib/modules/2.6.32-21-generic/build M=/usr/lib/parallels-tools/kmods/prl_eth/pvmnet make[2]: Entering directory `/usr/src/linux-headers-2.6.32-21-generic' LD /usr/lib/parallels-tools/kmods/prl_eth/pvmnet/built-in.o CC [M] /usr/lib/parallels-tools/kmods/prl_eth/pvmnet/pvmnet.o LD [M] /usr/lib/parallels-tools/kmods/prl_eth/pvmnet/prl_eth.o Building modules, stage 2. MODPOST 1 modules WARNING: modpost: missing MODULE_LICENSE() in /usr/lib/parallels-tools/kmods/prl_eth/pvmnet/prl_eth.o thanks

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• Inauguration Of My Laptop

  - by Pawan_Mishra

  Today I received my new laptop which is an Intel Core i5-2450M @ 2.50GHz 4 GB RAM machine . The other laptop(office provided) which I have used for past two years for programming is an Intel Core2 Duo T6570 @ 2.10GHz machine. Reason why I am talking about the laptops that I own is because of my interest in writing multi-threaded/parallel code using the new TPL API provided in the .Net 4.0 framework. I have spent significant amount of time in past one year writing code using the Parallel API of .Net...(read more)

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