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• How can I Export a Table in Access using VBA into a specific sheet in an Excel spreadsheet?

  - by Bryan

  I have a some tables, we will call them Table1,Table2.... and I need them to be Exported into specific spreadsheets in a macro enabled Excel File (.xlsm) that already exists. So I would need to put Table1 into Sheet2, Table2 into Sheet3... and so on. I had been doing this manually by going to the export menu in Access but it is getting monotonous so I would like to automate the process. The Excel file will already have code in each spreadsheet which would need to still be intact.

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• Copying Data to a Master sheet from other sheets without duplicates

  - by sam

  I have four workbooks, three of which are for data entries, and the latter which hosts all data entered in the other workbooks; as a matter of fact, it serves as a master workbook. I need code to copy data entered in each workbook in sheet 1 to be copied to the next available row on sheet 1 of the master workbook, but if the data to be copied from these individual workbooks are duplicates, then a message box should pop up displaying that its a duplicate. To be precise, I want the users to type p in column j indicating process, and click a button in the spreadsheet to copy the data to the master sheet. I would be glad for any assistance. Thanks a million for any help.

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• Formwizards for editing in Django

  - by Espen Christensen

  Hi, I am in the process of making a webapp, and this webapp needs to have a form wizard. The wizard consists of 3 ModelForms, and it works flawlessly. But I need the second form to be a "edit form". That is, i need it to be a form that is passed an instance. How can you do this with a form wizard? How do you pass in an instance of a model? I see that the FormWizard class has a get_form method, but isnt there a documented way to use the formwizard for editing/reviewing of data?

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• Python Imaging: YCbCr problems

  - by daver

  Hi, I'm doing some image processing in Python using PIL, I need to extract the luminance layer from a series of images, and do some processing on that using numpy, then put the edited luminance layer back into the image and save it. The problem is, I can't seem to get any meaningful representation of my Image in a YCbCr format, or at least I don't understand what PIL is giving me in YCbCr. PIL documentation claims YCbCr format gives three channels, but when I grab the data out of the image using np.asarray, I get 4 channels. Ok, so I figure one must be alpha. Here is some code I'm using to test this process: import Image as im import numpy as np pengIm = im.open("Data\\Test\\Penguins.bmp") yIm = pengIm.convert("YCbCr") testIm = np.asarray(yIm) grey = testIm[:,:,0] grey = grey.astype('uint8') greyIm = im.fromarray(grey, "L") greyIm.save("Data\\Test\\grey.bmp") I'm expecting a greyscale version of my image, but what I get is this jumbled up mess: http://i.imgur.com/zlhIh.png Can anybody explain to me where I'm going wrong? The same code in matlab works exactly as I expect.

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• Is there a sample set of web log data available for testing analysis against?

  - by Peter

  Sorry if this isn't strictly speaking a programming question, but I figure my best chance of success would be to ask here. I'm developing some web log file analysis algorithms, but to date I only have access to a fairly small amount of web log data to process. One algorithm I want to use makes some assumptions about 'the shape' of typical web log data, and so I'd like to test it against a larger 'exemplar' - perhaps the logs of a busy site with a good distribution of traffic from different sources etc. Is there a set of such data available somewhere? Thanks for any help.

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• Does Amazon S3's HTTP Uploads feature support web-hook style callbacks?

  - by Gabe Hollombe

  When uploading files to Amazon S3 using the browser http upload feature, I know I can specify a success_action_redirect field/value that will tell my browser where to go when the upload is done. I'm wondering: is it possible to ask Amazon to make a web hook style POST request to my web server whenever a file gets uploaded? Basically, I want a way of being notified whenever a client uploads a new file, so that my server can process the upload. I'd like to do this without relying on the client to make the request to my server to tell me the file has been uploaded (never trust the client, right?).

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• malloc()/free() behavior differs between Debian and Redhat

  - by StasM

  I have a Linux app (written in C) that allocates large amount of memory (~60M) in small chunks through malloc() and then frees it (the app continues to run then). This memory is not returned to the OS but stays allocated to the process. Now, the interesting thing here is that this behavior happens only on RedHat Linux and clones (Fedora, Centos, etc.) while on Debian systems the memory is returned back to the OS after all freeing is done. Any ideas why there could be the difference between the two or which setting may control it, etc.?

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• Does MATLAB perform tail call optimization?

  - by Shea Levy

  I've recently learned Haskell, and am trying to carry the pure functional style over to my other code when possible. An important aspect of this is treating all variables as immutable, i.e. constants. In order to do so, many computations that would be implemented using loops in an imperative style have to be performed using recursion, which typically incurs a memory penalty due to the allocation a new stack frame for each function call. In the special case of a tail call (where the return value of a called function is immediately returned to the callee's caller), however, this penalty can be bypassed by a process called tail call optimization (in one method, this can be done by essentially replacing a call with a jmp after setting up the stack properly). Does MATLAB perform TCO by default, or is there a way to tell it to?

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• svn hangs when connecting to server but only for me!

  - by vgm64

  I've checked out two repositories with svn and they both have some odd behavior when using commands like svn -u status. That command in particular will hang, and top says the process is sleeping. I can check out and update those repos (usually), but this in particular will hang until I kill -9 it. It doesn't happen on anyone else's computer (I'm running Mac OSX 10.6) who uses these repos. I just checked out a fresh clean version of one of the repos, and did svn -u status and it froze. Anyone have any thoughts? Could some settings be corrupted?

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• Why does A* path finding sometimes go in straight lines and sometimes diagonals? (Java)

  - by Relequestual

  I'm in the process of developing a simple 2d grid based sim game, and have fully functional path finding. I used the answer found in my previous question as my basis for implementing A* path finding. (http://stackoverflow.com/questions/735523/pathfinding-2d-java-game). To show you really what I'm asking, I need to show you this video screen capture that I made. I was just testing to see how the person would move to a location and back again, and this was the result... http://www.screenjelly.com/watch/Bd7d7pObyFo Different choice of path depending on the direction, an unexpected result. Any ideas?

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• Paypal IPN Confirmation Screen immediately after redirect without reload

  - by Email

  Hi I made a script for IPN which works great but how can i immediately notify the user? I mean paypal redirects the customer to a custom-page i can define, simultanously my ipn.php checked the status, BUT how can i immediately tell the customer on this custom-page that it was successful or not. this custom-page does somehow has to know that this is the customer-xyz which made the ipn-verified!!! payment xyz, but how? i think also this custom-page redirect should wait the 5 seconds because php does only process files/request on-loads... so after 5 seconds the ipnscript surely did complete. Sorry if this question is too newby but i dont know how to notify the customer about the (ipn-verified!!!) payment-status immediately. How do you do this? Thanks so much

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• Core dump utility for .NET

  - by Dave

  In my past life as a COBOL mainframe developer I made extensive use of a tool called Abendaid which, in the event of an exception, would give me a complete memory dump including a formatted list of every variable in memory as well as a complete stack trace of the program with the offending statement highlighted. This made pinpointing the cause of an error much simpler and saved a lot of step-through debugging and/or trace statements. Now I've made the transition to C# and .NET web development I find that the information provided by ASP.NET only tells half the story, giving me a stack trace, but not any of the variable or class information. This makes debugging more difficult as you then have to run the process again with the debugger to try and reproduce the error, not easy with intermittent errors or with assemblies that run under the likes of SQL Server or CRM. I've looked around quite a lot for something that does this but I can't find anything obvious. Does anyone have any idea if there is one, or if not, what I'd need to start with in order to write one?

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• a question on webpage data scraping using Java

  - by Gemma

  Hi there. I am now trying to implement a simple HTML webpage scraper using Java.Now I have a small problem. Suppose I have the following HTML fragment. <div id="sr-h-left" class="sr-comp"> <a class="link-gray-underline" id="compare_header" rel="nofollow" href="javascript:i18nCompareProd('/serv/main/buyer/ProductCompare.jsp?nxtg=41980a1c051f-0942A6ADCF43B802'); " Compare Showing 1 - 30 of 1,439 matches, The data I am interested is the integer 1.439 shown at the bottom.I am just wondering how can I get that integer out of the HTML. I am now considering using a regular expression,and then use the java.util.Pattern to help get the data out,but still not very clear about the process. I would be grateful if you guys could give me some hint or idea on this data scraping. Thanks a lot.

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• Can "\Device\NamedPipe\\Win32Pipes" handles cause "Too many open files" error?

  - by Igor Oks

  Continuing from this question: When I am trying to do fopen on Windows, I get a "Too many open files" error. I tried to analyze, how many open files I have, and seems like not too much. But when I executed Process Explorer, I noticed that I have many open handles with similar names: "\Device\NamedPipe\Win32Pipes.00000590.000000e2", "\Device\NamedPipe\Win32Pipes.00000590.000000e3", etc. I see that the number of these handles is exactly equal to the number of the iterations that my program executed, before it returned "Too many open files" and stopped. I am looking for an answer, what are these handles, and could they actually cause the "Too many open files" error? In my program I am loading files from remote drive, and I am creating TCP/IP connections. Could one of these operations create these handles?

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• Mysqld Crashes immediately on running on Windows 7...?

  - by Cyril Gupta

  I am trying to run MySql 5.1 on Windows 7 Home Premium 64 bit. I have downloaded the MSI installer from the MYSql website and installed it. The installation is successful, but the service does not start. If I try to run MySql manually using the mysqld executable, it crashes immediately on running (error: mysqld.exe has stopped working). Earlier mysql was running on the machine, but I had some problem with it (wasn't executing big queries) and installed it again which somehow broke the program. I had installed it to work as a service which started giving me this isse, and now it won't work even if I don't install it as a service. I have tried removing the mysql folder and re-installing. Is there somewhere else where Mysql saves configuration info or other data? Has anyone else found this problem and solved it? How can I find out why the process is failing to run?

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• Minimal Lunix distribution with sshd and apt

  - by Sergey Mikhanov

  When I signed up for my Debian Linux VPS hosting and first logged on and invoked ps aux, there was the only user process running: sshd. As I can see, this was minimal Linux with only two things installed and configured: sshd and apt (plus all dependencies, of course). I want to build (or use existing) similar Linux distro, any advice on how to build (or pick) one? Googling "minimum linux", or "linux with sshd only" usually brings up Debian's netinstall, which is not what I want. Thanks in advance.

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• Speech recognition with Flash or Silverlight

  - by Sebastián Grignoli

  I'm developing a web user interface to enter some information that is not very complex but needs to be loaded in real time. I think that the application could make use of speech recognition to facilitate the task. Te core of the interface is being built with Javascript and jQuery, but can easily include a flash or silverlight component. I believe that´s probably the way to go... I don't need to recognize everything that the user says, but only a few prerecorded commands. Also, I don't want the user to click on a button to specify the begining and the end of the spoken command. It should be detected live. Is there anything that does this? I would be grateful if anyone tells me about a complete solution, free or commercial, as well as any advice on capturing a sound stream from the mic and process it with flash or sliverlight. Sebastian.-

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• DirectX 9 HLSL vs. DirectX 10 HLSL: syntax the same?

  - by numerical25

  For the past month or so, I have been busting my behind trying to learn DirectX. So I've been mixing back back and forth between DirectX 9 and 10. One of the major changes I've seen in the two is how to process vectors in the graphics card. One of the drastic changes I notice is how you get the GPU to recognize your structs. In DirectX 9, you define the Flexible Vertex Formats. Your typical set up would be like this: #define CUSTOMFVF (D3DFVF_XYZRHW | D3DFVF_DIFFUSE) In DirectX 10, I believe the equivalent is the input vertex description: D3D10_INPUT_ELEMENT_DESC layout[] = { {"POSITION",0,DXGI_FORMAT_R32G32B32_FLOAT, 0 , 0, D3D10_INPUT_PER_VERTEX_DATA, 0}, {"COLOR",0,DXGI_FORMAT_R32G32B32A32_FLOAT, 0 , 12, D3D10_INPUT_PER_VERTEX_DATA, 0} }; I notice in DirectX 10 that it is more descriptive. Besides this, what are some of the drastic changes made, and is the HLSL syntax the same for both?

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• Django multiple generic_inline_formset in a view

  - by Can Burak Cilingir

  We have a bunch of formsets: EmailAddressInlineFormSet = generic_inlineformset_factory( EmailAddress, extra=1, exclude=["created_by","last_modified_by"]) emailaddressformset = EmailAddressInlineFormSet( instance=person, prefix="emailaddress") # [ more definitions ] and, in the view, we process them as: emailaddressformset = EmailAddressInlineFormSet( request.POST, instance=person, prefix="emailaddress") # [ more definitions ] So, nothing fancy or unordinary. The unfortunate or unordinary fact is, we have 15 of these formsets, one for email addresses, other for phone numbers etc. so the view code is ugly and not-so-manageable. What would be the most unhackish way to handle this number of formsets in a single view? At the end -i guess- I'm looking for a class or a functionality like multiple_generic_inline_formset and open to all kind of suggestions or discussions.

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• Taming the malloc/free beast -- tips & tricks

  - by roufamatic

  I've been using C on some projects for a master's degree but have never built production software with it. (.NET & Javascript are my bread and butter.) Obviously, the need to free() memory that you malloc() is critical in C. This is fine, well and good if you can do both in one routine. But as programs grow, and structs deepen, keeping track of what's been malloc'd where and what's appropriate to free gets harder and harder. I've looked around on the interwebs and only found a few generic recommendations for this. What I suspect is that some of you long-time C coders have come up with your own patterns and practices to simplify this process and keep the evil in front of you. So: how do you recommend structuring your C programs to keep dynamic allocations from becoming memory leaks?

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• a4j:commandButton causes full page reload on IE7

  - by Greg Charles

  Our process allows users to activate their account, and then configure e-mail preferences. We're using the tag: <a4j:commandButton id="activate" action="#{controller.agreeAction}" image="/img/ok.png" styleClass="activate-button" reRender="mainContent, sideBar" oncomplete="showEmailDialog();" /> This works fine on Firefox, but on IE, the showEmaiDialog() fires off to display the new dialog, and then the full page reloads, which instantly hides it again. I put in numerous alert() calls to make sure of what was happening. I see the e-mail dialog until I clear the final alert box in in the showEmailDialog() script, and then I see the alerts that I put into jQuery(document).ready(). Why does IE do a full page reload instead of just refreshing the requested sections?

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• Compiling flex file into dll.

  - by Szpilona

  Hi, I've got a lexer created with flex (cygwin). Normally I compile it to an .exe file. For the newest project I need a lexer to use in a bigger C# program running on Windows XP. Of course I can execute a file using System.Diagnostics.Process. But it is not the best solution for me as I want that program to run on several machines. How can I create a dll under cygwin having the source code of the lexer? Thanks in advance... Szpilona

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• Passing Text for command line

  - by Kasun

  Hi, I need to pass some text which is in richtext box to command line. This is my Button click even which start the cmd. private void button1_Click(object sender, EventArgs e) { ProcessStartInfo psi = new ProcessStartInfo { FileName = "cmd", Arguments = @"/k ""C:\Program Files\Microsoft Visual Studio 9.0\VC\bin\vcvars32.bat""", }; Process.Start(psi); } In my rich text box contain following text. include iostream using namespace std; int main() { cout << "Welcome to the wonderful world of C++!!!\n"; return 0; } Can anyone provide me necessary codes.

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• what's the purpose of fcntl with parameter F_DUPFD

  - by Daniel

  I traced an oracle process, and find it first open a file /etc/netconfig as file handle 11, and then duplicate it as 256 by calling fcntl with parameter F_DUPFD, and then close the original file handle 11. Later it read using file handle 256. So what's the point to duplicate the file handle? Why not just work on the original file handle? 12931: 0.0006 open("/etc/netconfig", O_RDONLY|O_LARGEFILE) = 11 12931: 0.0002 fcntl(11, F_DUPFD, 0x00000100) = 256 12931: 0.0001 close(11) = 0 12931: 0.0002 read(256, " # p r a g m a i d e n".., 1024) = 1024 12931: 0.0003 read(256, " t s t p i _ c".., 1024) = 215 12931: 0.0002 read(256, 0x106957054, 1024) = 0 12931: 0.0001 lseek(256, 0, SEEK_SET) = 0 12931: 0.0002 read(256, " # p r a g m a i d e n".., 1024) = 1024 12931: 0.0003 read(256, " t s t p i _ c".., 1024) = 215 12931: 0.0003 read(256, 0x106957054, 1024) = 0 12931: 0.0001 close(256) = 0

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• .NET Code Evolution

  - by Alois Kraus

  Originally posted on: http://geekswithblogs.net/akraus1/archive/2013/07/24/153504.aspxAt my day job I do look at a lot of code written by other people. Most of the code is quite good and some is even a masterpiece. And there is also code which makes you think WTF… oh it was written by me. Hm not so bad after all. There are many excuses reasons for bad code. Most often it is time pressure followed by not enough ambition (who cares) or insufficient training. Normally I do care about code quality quite a lot which makes me a (perceived) slow worker who does write many tests and refines the code quite a lot because of the design deficiencies. Most of the deficiencies I do find by putting my design under stress while checking for invariants. It does also help a lot to step into the code with a debugger (sometimes also Windbg). I do this much more often when my tests are red. That way I do get a much better understanding what my code really does and not what I think it should be doing. This time I do want to show you how code can evolve over the years with different .NET Framework versions. Once there was  time where .NET 1.1 was new and many C++ programmers did switch over to get rid of not initialized pointers and memory leaks. There were also nice new data structures available such as the Hashtable which is fast lookup table with O(1) time complexity. All was good and much code was written since then. At 2005 a new version of the .NET Framework did arrive which did bring many new things like generics and new data structures. The “old” fashioned way of Hashtable were coming to an end and everyone used the new Dictionary<xx,xx> type instead which was type safe and faster because the object to type conversion (aka boxing) was no longer necessary. I think 95% of all Hashtables and dictionaries use string as key. Often it is convenient to ignore casing to make it easy to look up values which the user did enter. An often followed route is to convert the string to upper case before putting it into the Hashtable. Hashtable Table = new Hashtable(); void Add(string key, string value) { Table.Add(key.ToUpper(), value); } This is valid and working code but it has problems. First we can pass to the Hashtable a custom IEqualityComparer to do the string matching case insensitive. Second we can switch over to the now also old Dictionary type to become a little faster and we can keep the the original keys (not upper cased) in the dictionary. Dictionary<string, string> DictTable = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase); void AddDict(string key, string value) { DictTable.Add(key, value); } Many people do not user the other ctors of Dictionary because they do shy away from the overhead of writing their own comparer. They do not know that .NET has for strings already predefined comparers at hand which you can directly use. Today in the many core area we do use threads all over the place. Sometimes things break in subtle ways but most of the time it is sufficient to place a lock around the offender. Threading has become so mainstream that it may sound weird that in the year 2000 some guy got a huge incentive for the idea to reduce the time to process calibration data from 12 hours to 6 hours by using two threads on a dual core machine. Threading does make it easy to become faster at the expense of correctness. Correct and scalable multithreading can be arbitrarily hard to achieve depending on the problem you are trying to solve. Lets suppose we want to process millions of items with two threads and count the processed items processed by all threads. A typical beginners code might look like this: int Counter; void IJustLearnedToUseThreads() { var t1 = new Thread(ThreadWorkMethod); t1.Start(); var t2 = new Thread(ThreadWorkMethod); t2.Start(); t1.Join(); t2.Join(); if (Counter != 2 * Increments) throw new Exception("Hmm " + Counter + " != " + 2 * Increments); } const int Increments = 10 * 1000 * 1000; void ThreadWorkMethod() { for (int i = 0; i < Increments; i++) { Counter++; } } It does throw an exception with the message e.g. “Hmm 10.222.287 != 20.000.000” and does never finish. The code does fail because the assumption that Counter++ is an atomic operation is wrong. The ++ operator is just a shortcut for Counter = Counter + 1 This does involve reading the counter from a memory location into the CPU, incrementing value on the CPU and writing the new value back to the memory location. When we do look at the generated assembly code we will see only inc dword ptr [ecx+10h] which is only one instruction. Yes it is one instruction but it is not atomic. All modern CPUs have several layers of caches (L1,L2,L3) which try to hide the fact how slow actual main memory accesses are. Since cache is just another word for redundant copy it can happen that one CPU does read a value from main memory into the cache, modifies it and write it back to the main memory. The problem is that at least the L1 cache is not shared between CPUs so it can happen that one CPU does make changes to values which did change in meantime in the main memory. From the exception you can see we did increment the value 20 million times but half of the changes were lost because we did overwrite the already changed value from the other thread. This is a very common case and people do learn to protect their  data with proper locking.   void Intermediate() { var time = Stopwatch.StartNew(); Action acc = ThreadWorkMethod_Intermediate; var ar1 = acc.BeginInvoke(null, null); var ar2 = acc.BeginInvoke(null, null); ar1.AsyncWaitHandle.WaitOne(); ar2.AsyncWaitHandle.WaitOne(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Intermediate did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Intermediate() { for (int i = 0; i < Increments; i++) { lock (this) { Counter++; } } } This is better and does use the .NET Threadpool to get rid of manual thread management. It does give the expected result but it can result in deadlocks because you do lock on this. This is in general a bad idea since it can lead to deadlocks when other threads use your class instance as lock object. It is therefore recommended to create a private object as lock object to ensure that nobody else can lock your lock object. When you read more about threading you will read about lock free algorithms. They are nice and can improve performance quite a lot but you need to pay close attention to the CLR memory model. It does make quite weak guarantees in general but it can still work because your CPU architecture does give you more invariants than the CLR memory model. For a simple counter there is an easy lock free alternative present with the Interlocked class in .NET. As a general rule you should not try to write lock free algos since most likely you will fail to get it right on all CPU architectures. void Experienced() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); t1.Wait(); t2.Wait(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Experienced did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Experienced() { for (int i = 0; i < Increments; i++) { Interlocked.Increment(ref Counter); } } Since time does move forward we do not use threads explicitly anymore but the much nicer Task abstraction which was introduced with .NET 4 at 2010. It is educational to look at the generated assembly code. The Interlocked.Increment method must be called which does wondrous things right? Lets see: lock inc dword ptr [eax] The first thing to note that there is no method call at all. Why? Because the JIT compiler does know very well about CPU intrinsic functions. Atomic operations which do lock the memory bus to prevent other processors to read stale values are such things. Second: This is the same increment call prefixed with a lock instruction. The only reason for the existence of the Interlocked class is that the JIT compiler can compile it to the matching CPU intrinsic functions which can not only increment by one but can also do an add, exchange and a combined compare and exchange operation. But be warned that the correct usage of its methods can be tricky. If you try to be clever and look a the generated IL code and try to reason about its efficiency you will fail. Only the generated machine code counts. Is this the best code we can write? Perhaps. It is nice and clean. But can we make it any faster? Lets see how good we are doing currently. Level Time in s IJustLearnedToUseThreads Flawed Code Intermediate 1,5 (lock) Experienced 0,3 (Interlocked.Increment) Master 0,1 (1,0 for int[2]) That lock free thing is really a nice thing. But if you read more about CPU cache, cache coherency, false sharing you can do even better. int[] Counters = new int[12]; // Cache line size is 64 bytes on my machine with an 8 way associative cache try for yourself e.g. 64 on more modern CPUs void Master() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Master, 0); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Master, Counters.Length - 1); t1.Wait(); t2.Wait(); Counter = Counters[0] + Counters[Counters.Length - 1]; if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Master did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Master(object number) { int index = (int) number; for (int i = 0; i < Increments; i++) { Counters[index]++; } } The key insight here is to use for each core its own value. But if you simply use simply an integer array of two items, one for each core and add the items at the end you will be much slower than the lock free version (factor 3). Each CPU core has its own cache line size which is something in the range of 16-256 bytes. When you do access a value from one location the CPU does not only fetch one value from main memory but a complete cache line (e.g. 16 bytes). This means that you do not pay for the next 15 bytes when you access them. This can lead to dramatic performance improvements and non obvious code which is faster although it does have many more memory reads than another algorithm. So what have we done here? We have started with correct code but it was lacking knowledge how to use the .NET Base Class Libraries optimally. Then we did try to get fancy and used threads for the first time and failed. Our next try was better but it still had non obvious issues (lock object exposed to the outside). Knowledge has increased further and we have found a lock free version of our counter which is a nice and clean way which is a perfectly valid solution. The last example is only here to show you how you can get most out of threading by paying close attention to your used data structures and CPU cache coherency. Although we are working in a virtual execution environment in a high level language with automatic memory management it does pay off to know the details down to the assembly level. Only if you continue to learn and to dig deeper you can come up with solutions no one else was even considering. I have studied particle physics which does help at the digging deeper part. Have you ever tried to solve Quantum Chromodynamics equations? Compared to that the rest must be easy ;-). Although I am no longer working in the Science field I take pride in discovering non obvious things. This can be a very hard to find bug or a new way to restructure data to make something 10 times faster. Now I need to get some sleep ….

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