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• Programming cookbook? [closed]

  - by user73669

  Possible Duplicate: What is the single most influential book every programmer should read? Hello With sites like The Daily WTF and recurring threads on Slashdot and elsewhere about bad programming, I figured that, to avoid people reinventing the wheel (badly or not), there should be a good, fat book on programming that would go through typical programming problems and show good, known algorithms, either in pseudo-code or some language with an easy syntax so that the language is not an issue. Here's the list of books on the subject I saw at my local computer bookstore. Can you recommend a couple, or add to this list if it's missing better options? The art of computer programming Code complete Masterminds of programming 97 things every programmer should know The passionate programmer Pragmatic thinking & learning Coders at work The algorithm design manual Algorithms and programming How to think about algorithms How to think like a programmer Why programs fail Beautiful data Beautiful code The productive programmer Solid code Write great code Clean code Programming language pragmatics Hello world Learning Processing Learn to program Thank you.

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• Multithreading with STL container

  - by Steven

  I have an unordered map which stores a pointer of objects. I am not sure whether I am doing the correct thing to maintain the thread safety. typedef std::unordered_map<string, classA*>MAP1; MAP1 map1; pthread_mutex_lock(&mutexA) if(map1.find(id) != map1.end()) { pthread_mutex_unlock(&mutexA); //already exist, not adding items } else { classA* obj1 = new classA; map1[id] = obj1; obj1->obtainMutex(); //Should I create a mutex for each object so that I could obtain mutex when I am going to update fields for obj1? pthread_mutex_unlock(&mutexA); //release mutex for unordered_map so that other threads could access other object obj1->field1 = 1; performOperation(obj1); //takes some time obj1->releaseMutex(); //release mutex after updating obj1 }

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• How to implement HeightMap smoothing using Thrust

  - by igal k

  I'm trying to implement height map smoothing using Thrust. Let's say I have a big array ( around 1 million floats). A known graphics algorithm to implement the above problem is to calculate the average around a given cell. If for example I need to calculate the value at a given cell[i,j] what I will basically do is: cell[i,j] = cell[i-1,j-1] + cell[i-1,j] + cell[i-1,j+1] + cell[i,j-1] + cell[i,j+1] + cell[i+1,j -1] + cell[i+1,j] + cell[i+1,j+1] cell[i,j] /=9 That's the CPU code. Is there a way to implement it using thrust? I know that I could use the transform algorithm. But I'm not sure it's correct to access different cells which are occupied but different threads (banks conflicts and so on).

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• FACEBOOK LINTER ERROR: value for property 'og:image:url' could not be parsed as type 'url'

  - by Martin Devarda

  I've read all threads in stack overflow about this issue, but my problem persists. THE PROBLEM IS ON THIS PAGE: http://www.organirama.it/minisite-demo/001.html THE PAGE CONTAINS THIS TAGS <meta property="og:title" content="A wonderful page" /> <meta property="og:type" content="video.movie" /> <meta property="og:url" content="http://www.organirama.com/minisite-demo/001.html" /> <meta property="og:image" content="http:/www.organirama.com/minisite-demo/photos-small/001.png" /> <meta property="og:site_name" content="Organirama"/> <meta property="fb:admins" content="1468447924"/> LINTER ERROR Object at URL 'http://www.organirama.com/minisite-demo/001.html' of type 'video.movie' is invalid because the given value 'http:/www.organirama.com/minisite-demo/photos-small/001.png' for property 'og:image:url' could not be parsed as type 'url'. WHAT I DISCOVERED The problem seems somehow related to the domain. Infact, if I make og:image point to another image on another domain, everything works.

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• What's a good algorithm for searching arrays N and M, in order to find elements in N that also exist

  - by GenTiradentes

  I have two arrays, N and M. they are both arbitrarily sized, though N is usually smaller than M. I want to find out what elements in N also exist in M, in the fastest way possible. To give you an example of one possible instance of the program, N is an array 12 units in size, and M is an array 1,000 units in size. I want to find which elements in N also exist in M. (There may not be any matches.) The more parallel the solution, the better. I used to use a hash map for this, but it's not quite as efficient as I'd like it to be. Typing this out, I just thought of running a binary search of M on sizeof(N) independent threads. (Using CUDA) I'll see how this works, though other suggestions are welcome.

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• Minimizing Java Thread Context Switching Overhead

  - by binil

  I have a Java application running on Sun 1.6 32-bit VM/Solaris 10 (x86)/Nahelem 8-core(2 threads per core). A specific usecase in the application is to respond to some external message. In my performance test environment, when I prepare and send the response in the same thread that receives the external input, I get about 50 us advantage than when I hand off the message to a separate thread to send the response. I use a ThreadPoolExecutor with a SynchronousQueue to do the handoff. In your experience what is the acceptable delay between scheduling a task to a thread pool and it getting picked up for execution? What ideas had worked for you in the past to try improve this?

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• Java Thread - Synchronization issue

  - by Yatendra Goel

  From Sun's tutorial: Synchronized methods enable a simple strategy for preventing thread interference and memory consistency errors: if an object is visible to more than one thread, all reads or writes to that object's variables are done through synchronized methods. (An important exception: final fields, which cannot be modified after the object is constructed, can be safely read through non-synchronized methods, once the object is constructed) This strategy is effective, but can present problems with liveness, as we'll see later in this lesson. Q1. Is the above statements mean that if an object of a class is going to be shared among multiple threads, then all instance methods of that class (except getters of final fields) should be made synchronized, since instance methods process instance variables?

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• Which method should I use to give the perception the computer is thinking in programming?

  - by Roy

  I want to create a simple game like tic tac toe where the human user is playing against the computer. The computer function takes a couple of milliseconds to run but I would like to make the computer take 5 seconds to make a move. Which method should I use? 1) Create two memory threads. One for the computer and one for the human user. When the computer is taking 5 seconds to imitate thinking, the human user thread is paused for 5 seconds. 2) Disable input devices for 5 seconds using timer or dispatchertimer 3) Any better methods you can think of Thanks!

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• SSIS - Limiting Concurrent Connections

  - by Bigtoe

  Hi Folks, I am using SSIS to connect to a legecy mainframe database and this allows only 5 concurrent connections at a time. I have a dataflow task with many tables to transfer and it kicks outs because of this limitation. I have split up the Data Flow task into seperate data flows and this is working for the moment, but it is not optiomal as they need to be sequenced and 1 large transfer in a flow is holding up subsequent transfers. Anyone any idea of how to limit the number of connections in a single data flow, I had a look at using the Engine Threads but this did not make any difference. Any help much appericated.

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• passing parameters to a thread

  - by assassin

  I want to pass a function that takes a parameter to the ThreadStart Constructor in C#. But, it seems that this is not possible, as I get a syntax error it I try to do something like this Thread t1 = new Thread(new Thread Start(func1(obj1)); where obj1 is an object of type List<string> (say). If I want a thread to execute this function that takes in an object as a parameter, and I plan to create 2 such threads simultaneously with different parameter values what is the best method to achieve this?

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• Millisecond-Accurate Scheduling of Future Events in C++/CLI

  - by A Grad Student at a University

  I need to create a C++/CLI mixed assembly that can schedule future calls into a native DLL with millisecond accuracy. This will, of course, mean setting a timer (what kind?) for a millisecond or three beforehand, then spinning until the moment and calling the native DLL function. Based on what I've read, I would guess that the callback that the timer calls will need to be native to make sure there are no thunks or GC to delay handling the timer callback. Will the entire thread or process need to be native and CLR-free, though, or can this be done just as accurately with #pragma unmanaged or setting one file of the assembly to compile as native? If so, how? If there is indeed no way to do this in mixed-mode C++/CLI, what would be the easiest way to set up an app/thread (ie, DLL or exe?) to handle it and to get the data back and forth between the native and managed threads/apps?

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• Why are Asynchronous processes not called Synchronous?

  - by Balk

  So I'm a little confused by this terminology. Everyone refers to "Asynchronous" computing as running different processes on seperate threads, which gives the illusion that these processes are running at the same time. This is not the definition of the word asynchronous. a·syn·chro·nous –adjective 1. not occurring at the same time. 2. (of a computer or other electrical machine) having each operation started only after the preceding operation is completed. What am I not understanding here?

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• DispatcherOperations.Wait()

  - by Mark

  What happens if you call dispatcherOperation.Wait() on an operation that has already completed? Also, the docs say that it returns a DispatcherOperationStatus, but wouldn't that always be Completed since it (supposedly) doesn't return until it's done? I was trying to use it like this: private void Update() { while (ops.Count > 0) ops.Dequeue().Wait(); } public void Add(T item) { lock (sync) { if (dispatcher.CheckAccess()) { list.Add(item); OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, item)); } else { ops.Enqueue(dispatcher.BeginInvoke(new Action<T>(Add), item)); } } } I'm using this in WPF, so all the Add operations have to occur on the UI thread, but I figured I could basically just queue them up without having to wait for it to switch threads, and then just call Update() before any read operations to ensure that the list is up to date, but my program started hanging.

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• Basic QT Event handling / Threading questions ?

  - by umanga

  Greetings , I am new to QT (4.6) and have some basic questions regarding its event mechanism.I come from Swing background so I am trying to compare it with QT. 1) Does Event-processing-loop run in seperate thread? (like EventDispatch thread in Swing) ? 2) If we open several 'QMainWindow' do they run in several threads? 3) Whats the best way to run an intensive process in a seperate thread? (like SwingWorker in Swing ? ) 4) If intesive-process runs in a seperate thread ,is it possible to call UI methods like update(),repaint() from that process? thanks in advance.

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• Fast way to pass a simple java object from one thread to another

  - by Adal

  I have a callback which receives an object. I make a copy of this object, and I must pass it on to another thread for further processing. It's very important for the callback to return as fast as possible. Ideally, the callback will write the copy to some sort of lock-free container. I only have the callback called from a single thread and one processing thread. I only need to pass a bunch of doubles to the other thread, and I know the maximum number of doubles (around 40). Any ideas? I'm not very familiar with Java, so I don't know the usual ways to pass stuff between threads.

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• Globals across modules

  - by Coder1

  Wow, this seems so basic, but I can't get it to work. All I need to do is store a global dict which can be accessed and modified from other modules & threads. What's the "best practices" way of achieving this? test.py import testmodule class MyClassA(): def __init__(self, id): self.id = id if __name__ == '__main__': global classa_dict classa_dict = {} classa_dict[1] = MyClassA(1) classa_dict[2] = MyClassA(2) testing = testmodule.TestModule() testmodule.py class TestModule(): def __init__(self): global classa_dict print classa_dict[2] output $ python test.py Traceback (most recent call last): File "test.py", line 13, in <module> testing = testmodule.TestModule() File "/path/to/project/testmodule.py", line 4, in __init__ print classa_dict[2] NameError: global name 'classa_dict' is not defined

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• Android ImageButton / Custom-Button?

  - by user568306

  Hi everyone, I am new to android development. So far I could help myself in all matters by reading threads here on stackoverflow. Now I am stuck and need someones help. Unfortunately I am not allowed to post an image of a screenshot because I am a new mamber, so I try to descripe it. I have a Samsung Galasy S and the clock app that ships with it has an button called "+ Create alarm". I want to create a similar button for my app. I've been experimenting with ImageButton. I do know how to get that "+"-Icon onto an ImageButton, but only centered and without text. I guess this is a custom button. Does anyone know how to do this? Can I do it in xml or do I need to extend the view-class and make it my own view?

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• implementing keepalives with Java

  - by Bilal

  Hi All, I am biulding a client-server application where I have to implement a keepalive mechanism in order to detect that the client has crashed or not. I have separate threads on both client and server side. the client thread sends a "ping" then sleeps for 3 seconds, while the server reads the BufferedInput Stream and checks whether ping is received, if so it makes the ping counter eqauls zero, else it increments the counter by +1, the server thread then sleeps for 3 seconds, if the ping counter reaches 3, it daclares the client as dead. The problem is that when the server reads the input stream, its a blocking call, and it blocks untill the next ping is received, irrespective of how delayed it is, so the server never detects a missed ping. any suggestions, so that I can read the current value of the stream and it doesn't block if there is nothing on the incoming stream. Thanks,

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• Why are most really fast servers written in C instead of C++?

  - by orokusaki

  I'm trying to decide which to learn and I've read all the "Which is better" questions/arguments, so I thought I'd get your take on something more specific. Is there a platform dependency issue that C++ developers run into with such applications? Or, is it because there are more C developers out there than C++? I also noticed that many more third party C modules exist for Python even thought C++ modules are supported. From what I've read on different threads the consensus is that C++ is easier and faster to write, and runs just as fast. Am I missing something really big. Examples: NGINX APE (comet server) Apache

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• why single SQL delete statement will cause deadlock?

  - by George2

  Hello everyone, I am using SQL Server 2008 Enterprise. I am wondering why even a single delete statement of this store procedure will cause deadlock if executed by multiple threads at the same time? For the delete statement, Param1 is a column of table FooTable, Param1 is a foreign key of another table (refers to another primary key clustered index column of the other table). There is no index on Param1 itself for table FooTable. FooTable has another column which is used as clustered primary key, but not Param1 column. create PROCEDURE [dbo].[FooProc] ( @Param1 int ,@Param2 int ,@Param3 int ) AS DELETE FooTable WHERE Param1 = @Param1 INSERT INTO FooTable ( Param1 ,Param2 ,Param3 ) VALUES ( @Param1 ,@Param2 ,@Param3 ) DECLARE @ID bigint SET @ID = ISNULL(@@Identity,-1) IF @ID > 0 BEGIN SELECT IdentityStr FROM FooTable WHERE ID = @ID END thanks in advance, George

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• how to find out how much application memory django process is (or will be) taking?

  - by photographer

  There are different "Application memory" options (like 80MB...200MB) in django-friendly hosting called webfaction and I'm confused deciding which one I should buy. Could someone please walk me through the ideas on how to figure out how much memory my project might require (excluding operating system, the main apache server and the database servers memory requirements)? I understand in theory I'll need to perform some kind of load testing, but thought there might be ways to calculate that in advance with some simple/relatively easy understandable approach. I don't know how hard they enforce application memory usage limit, and another question is: what will happen if more users came to the site and more threads started than what I expected? Will the application crash? Or will delays just become uncomfortable? And - no, application is not ready yet (I can't measure anything right now). Development environment if it matters is Winodows 7, 64-bit. Hosting itself is some kind of Linux I think. (Sorry if it's not a stackoverflow question.)

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• Updating a modul leve shared dictionary

  - by Vishal

  Hi, A module level dictionary 'd' and is accessed by different threads/requests in a django web application. I need to update 'd' every minute with a new data and the process takes about 5 seconds. What could be best solution where I want the users to get either the old value or the new value of d and nothing in between. I can think of a solution where a temp dictionary is constructed with a new data and assigned to 'd' but not sure how this works! Appreciate your ideas. Thanks

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• pthreads recursively calling system command and segfault appears

  - by jess

  I have a code base where i am creating 8 threads and each thread just calls system command to display date in a continuous cycle, as shown below: void * system_thread(void *arg) { int cpu = (int)arg; printf("thread : start %d\n", cpu); for (;;) { // date ã³ãã³ãã®å®è¡ if (mode == 0) { system("date"); } else { f_hfp_nlc_Fsystem("date"); } } sleep(timerval); return NULL; } This application segfaults after running for 2-3 seconds, due to following 2 reasons: 1. read access, where the address is out of VM area 2. write acces, where it does not of write permission and its trying to modify some structure.

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• ArrayBlockingQueue exceeds given capacity

  - by Wojciech Reszelewski

  I've written program solving bounded producer & consumer problem. While constructing ArrayBlockingQueue I defined capacity 100. I'm using methods take and put inside threads. And I've noticed that sometimes I see put 102 times with any take's between them. Why does it happen? Producer run method: public void run() { Object e = new Object(); while(true) { try { queue.put(e); } catch (InterruptedException w) { System.out.println("Oj, nie wyszlo, nie bij"); } System.out.println("Element added"); } } Consumer run method: public void run() { while(true) { try { queue.take(); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("Element removed"); } } Part of uniq -c on file with output: 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 2 Element removed 2 Element added 102 Element removed 102 Element added

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• Android: Touch seriously slowing my application

  - by Jason Rogers

  Hi all, I've been raking my brains on this one for a while. when I'm running my application (opengl game) eveyrthing goes fine but when I touch the screen my application slows down quite seriously (not noticeable on powerful phones like the nexus one, but on the htc magic it gets quite annoying). I did a trace and found out that the touch events seem to be handled in a different thread and even if it doesn't take so much processing time I think androids ability to switch between threads is not so good... What is the best way to handle touch when speed is an issue ? Currently I'm using : in the GLSurfaceView @Override public boolean onTouchEvent(MotionEvent event) { GameHandler.onTouchEvent(event); return true; } Any ideas are welcome

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