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  • How to buffer stdout in memory and write it from a dedicated thread

    - by NickB
    I have a C application with many worker threads. It is essential that these do not block so where the worker threads need to write to a file on disk, I have them write to a circular buffer in memory, and then have a dedicated thread for writing that buffer to disk. The worker threads do not block any more. The dedicated thread can safely block while writing to disk without affecting the worker threads (it does not hold a lock while writing to disk). My memory buffer is tuned to be sufficiently large that the writer thread can keep up. This all works great. My question is, how do I implement something similar for stdout? I could macro printf() to write into a memory buffer, but I don't have control over all the code that might write to stdout (some of it is in third-party libraries). Thoughts? NickB

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  • What strategies are efficient to handle concurrent reads on heterogeneous multi-core architectures?

    - by fabrizioM
    I am tackling the challenge of using both the capabilities of a 8 core machine and a high-end GPU (Tesla 10). I have one big input file, one thread for each core, and one for the the GPU handling. The Gpu thread, to be efficient, needs a big number of lines from the input, while the Cpu thread needs only one line to proceed (storing multiple lines in a temp buffer was slower). The file doesn't need to be read sequentially. I am using boost. My strategy is to have a mutex on the input stream and each thread locks - unlocks it. This is not optimal because the gpu thread should have a higher precedence when locking the mutex, being the fastest and the most demanding one. I can come up with different solutions but before rush into implementation I would like to have some guidelines. What approach do you use / recommend ?

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  • iphone threading speed up startup of app

    - by BahaiResearch.com
    I have an app that must get data from the Sqlite database in order to display the first element to the User. I have created a domain object which wraps the DB access and is a thread safe singleton. Is this following strategy optimal to ensure the fastest load given the iPhone's file access and memory management capabilities in threaded apps: 1) In the AppDelegate's FinishedLaunching event the very first thing I do is create the domain singleton within a new thread. This will cause the domain object to go to Sqlite and get the data it needs without locking the UI thread. 2) I then call the standard Window methods to add the View and MakeKeyAndVisible etc. Is there an earlier stage in the AppDelegate where I should fire off the thread that creates the Domain Object and accesses Sqlite?

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  • Will this make the object thread-safe?

    - by sharptooth
    I have a native Visual C++ COM object and I need to make it completely thread-safe to be able to legally mark it as "free-threaded" in th system registry. Specifically I need to make sure that no more than one thread ever accesses any member variable of the object simultaneously. The catch is I'm almost sure that no sane consumer of my COM object will ever try to simultaneously use the object from more than one thread. So I want the solution as simple as possible as long as it meets the requirement above. Here's what I came up with. I add a mutex or critical section as a member variable of the object. Every COM-exposed method will acquire the mutex/section at the beginning and release before returning control. I understand that this solution doesn't provide fine-grained access and this might slow execution down, but since I suppose simultaneous access will not really occur I don't care of this. Will this solution suffice? Is there a simpler solution?

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  • event vs thread programming on server side.

    - by AlxPeter
    We are planning to start a fairly complex web-portal which is expected to attract good local traffic and I've been told by my boss to consider/analyse node.js for the serve side. I think scalability and multi-core support can be handled with an Nginx or Cherokee up in the front. 1) Is this node.js ready for some serious/big business? 2) Does this 'event/asynchronous' paradigm on server side has the potential to support the heavy traffic and data operation ? considering the fact that 'everything' is being processed in a single thread and all the live connections would be lost if it got crashed (though its easy to restart). 3) What are the advantages of event based programming compared to thread based style ? or vice-versa. (I know of higher cost associated with thread switching but hardware can be squeezed with event model.) Following are interesting but contradicting (to some extent) papers:- 1) http://www.usenix.org/events/hotos03/tech/full_papers/vonbehren/vonbehren_html 2) http://pdos.csail.mit.edu/~rtm/papers/dabek:event.pdf

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  • How to kill a thread immediately from another thread in java?

    - by Sara
    Hi, is there anyway to kill a thread or interrupt it immediately. Like in one of my thread, i call a method which takes time to execute (2-4 seconds). This method is in a while(boolean flag) block, so i can interrupt it from the main thread. But the problem is, if i interrupt it; it will wait till the executing loop is finished and then on next conditional check, it will stop execution. I want it to stop right then. Is there anyway to do this?

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  • prevent linux thread from being interrupted by scheduler

    - by johnnycrash
    How do you tell the thread scheduler in linux to not interrupt your thread for any reason? I am programming in user mode. Does simply locking a mutex acomplish this? I want to prevent other threads in my process from being scheduled when a certain function is executing. They would block and I would be wasting cpu cycles with context switches. I want any thread executing the function to be able to finish executing without interruption even if the threads' timeslice is exceeded.

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  • c++ simple start a function with its own thread

    - by user1397417
    i had once had a very simple one or two line code that would start a function with its own thread and continue running until application closed, c++ console app. lost the project it was in, and remember it was hard to find. cant find it online now. most example account for complicated multithreading situations. but i just need to open this one function in its own thread. hopefully someone knows what im talking about, or a similar solution. eg. start void abc in its own thread, no parameters

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  • Referenced assembly won't load in new thread on IIS 7

    - by DanielC
    I have a process in which a user uploads a file to a web site where the file is then processed and uploaded into the database. The process of validating the file could take several minutes so as soon as the file is uploaded I create a new thread and I do my processing on this second thread. This works great on my local machine but doesn't work at all on my IIS 7 test server. After some investigating I found the problem is that the process is trying to load a reference to Castle and it can't find the DLL. I have a copy of Castle DLLs in my bin and it works elsewhere in my app. I ran Fuslog and discovered that it is trying to load castle from the wrong location. It is trying to load from c:/windows/system32/inetsrv/. It appears that under IIS 7 the second thread is executing in a different context or something. So the question is what can I do to get it to find Castle in the application BIN folder?

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  • Reason for .Net UI Element Thread-restriction

    - by Charles Bretana
    We know that it is not possible to execute code that manipulates the properties of any UI element from any thread other than the thread the element was instantiated on... My question is why? I remember that when we used COM user interface elements, (in COM/VB6 days), that all UI elements were created using COM classes and co-classes that stored their resources using a memory model referred to as Thread-Local-Storage (TLS) , but as I recall, this was required because of something relaetd to the way COM components were constructed, and should not be relevant to .Net UI elements. Wha's the underlying reason why this restriction still exists? Is it because the underlying Operating System still uses COM-based Win32 API classes for all UI elements, even the ones manipulated in a managed .Net application ??

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  • C# Dispatcher {"The calling thread cannot access this object because a different thread owns it."}

    - by user359446
    Hi, first I need to say that I´m noob with WPF and C#. Application: Create Mandelbrot Image (GUI) My disptacher works perfektly this this case: private void progressBarRefresh(){ while ((con.Progress) < 99) { progressBar1.Dispatcher.Invoke(DispatcherPriority.Send, new Action(delegate { progressBar1.Value = con.Progress; } )); } } I get the Message (Title) when tring to do this with the below code: bmp = BitmapSource.Create(width, height, 96, 96, pf, null, rawImage, stride); this.Dispatcher.Invoke(DispatcherPriority.Send, new Action(delegate { img.Source = bmp; ViewBox.Child = img; //vllt am schluss } )); I will try to explain how my program works. I created a new Thread (because GUI dont response) for the calculation of the pixels and the colors. In this Thread(Mehtod) I´m using the Dispatcher to Refresh my Image in the ViewBox after the calculations are ready. When I´m dont put the calculation in a seperate Thread then I can refresh or build my Image. PS: Sry for my bad english

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  • Datagridview retains waitcursor when updated from thread

    - by Apeksha
    I have a DataGridView control in my Windows Forms Application. I am adding rows to the grid using a background thread. I change the form's cursor to Waitcursor when the process starts and back to Default when it ends. This works well for the form, but not for the grid. When the form's cursor is changed back to default, the grid's cursor does not change, although the cursor over the rest of the form does. Does this have anything to do with the fact that I am updating the grid from a background thread? (The cursor is being changed from the UI thread).

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  • OpenGL multiple threads, variable handling [closed]

    - by toeplitz
    I have written an OpenGL program which runs in the following way: Main: - Initialize SDL - Create thread which has the OpenGL context: - Renderloop - Set camera (view) matrix with glUniform. - glDrawElements() .... etc. - Swapbuffers(); - Main SDL loop handling input events and such. - Update camera matrix of type glm::mat4. This is how I pass my camera object to the class that handles opengl. Camera *cam = new Camera(); gl.setCam(cam); where void setCam(Camera *camera) { this->camera = camera; } For rendering in the opengl context thread, this happens: glm::mat4 modelView = camera->view * model; glUniformMatrix4fv(shader->bindUniform("modelView"), 1, GL_FALSE, glm::value_ptr(modelView)); In the main program where my SDL and other things are handles I then recompute the view matrix. This his working fine without me using any mutex locks. Is this correct? On the other hand, I add objects to my scene by an "upload queue" and in this case I have to mutex lock my upload queue vector (vector class type) when adding items to it or else the program crashes. In summary: I recompute my matrix in a different thread and then use it in the opengl thread without any mutex lock. Why is this working? Edit: I think my question is similar to what was asked here: Should I lock a variable in one thread if I only need it's value in other threads, and why does it work if I don't?, only in my case it is even more simple with only one matrix being changed.

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  • Trouble in ActiveX multi-thread invoke javascript callback routine

    - by code0tt
    everyone. I'm get some trouble in ActiveX programming with ATL. I try to make a activex which can async-download files from http server to local folder and after download it will invoke javascript callback function. My solution: run a thread M to monitor download thread D, when D is finish the job, M is going to terminal themself and invoke IDispatch inferface to call javascript function. **************** THERE IS MY CODE: **************** /* javascript code */ funciton download() { var xfm = new ActiveXObject("XFileMngr.FileManager.1"); xfm.download( 'http://somedomain/somefile','localdev:\\folder\localfile',function(msg){alert(msg);}); } /* C++ code */ // main routine STDMETHODIMP CFileManager::download(BSTR url, BSTR local, VARIANT scriptCallback) { CString csURL(url); CString csLocal(local); CAsyncDownload download; download.Download(this, csURL, csLocal, scriptCallback); return S_OK; } // parts of CAsyncDownload.h typedef struct tagThreadData { CAsyncDownload* pThis; } THREAD_DATA, *LPTHREAD_DATA; class CAsyncDownload : public IBindStatusCallback { private: LPUNKNOWN pcaller; CString csRemoteFile; CString csLocalFile; CComPtr<IDispatch> spCallback; public: void onDone(HRESULT hr); HRESULT Download(LPUNKNOWN caller, CString& csRemote, CString& csLocal, VARIANT callback); static DWORD __stdcall ThreadProc(void* param); }; // parts of CAsyncDownload.cpp void CAsyncDownload::onDone(HRESULT hr) { if(spCallback) { TRACE(TEXT("invoke callback function\n")); CComVariant vParams[1]; vParams[0] = "callback is working!"; DISPPARAMS params = { vParams, NULL, 1, 0 }; HRESULT hr = spCallback->Invoke(0, IID_NULL, LOCALE_USER_DEFAULT, DISPATCH_METHOD, &params, NULL, NULL, NULL); if(FAILED(hr)) { CString csBuffer; csBuffer.Format(TEXT("invoke failed, result value: %d \n"),hr); TRACE(csBuffer); }else { TRACE(TEXT("invoke was successful\n")); } } } HRESULT CAsyncDownload::Download(LPUNKNOWN caller, CString& csRemote, CString& csLocal, VARIANT callback) { CoInitializeEx(NULL, COINIT_MULTITHREADED); csRemoteFile = csRemote; csLocalFile = csLocal; pcaller = caller; switch(callback.vt){ case VT_DISPATCH: case VT_VARIANT:{ spCallback = callback.pdispVal; } break; default:{ spCallback = NULL; } } LPTHREAD_DATA pData = new THREAD_DATA; pData->pThis = this; // create monitor thread M HANDLE hThread = CreateThread(NULL, 0, ThreadProc, (void*)(pData), 0, NULL); if(!hThread) { delete pData; return HRESULT_FROM_WIN32(GetLastError()); } WaitForSingleObject(hThread, INFINITE); CloseHandle(hThread); CoUninitialize(); return S_OK; } DWORD __stdcall CAsyncDownload::ThreadProc(void* param) { LPTHREAD_DATA pData = (LPTHREAD_DATA)param; // here, we will create http download thread D // when download job is finish, call onDone method; pData->pThis->onDone(S_OK); delete pData; return 0; } **************** CODE FINISH **************** OK, above is parts of my source code, if I call onDone method in sub-thread, I will get OLE ERROR(-2147418113 (8000FFFF) Catastrophic failure.). Did I miss something? please help me to figure it out.

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  • Floating point comparison in STL, BOOST

    - by Paul
    Is there in the STL or in Boost a set of generic simple comparison functions? The one I found are always requiring template parameters, and/or instantiation of a struct template. I'm looking for something with a syntax like : if ( is_greater(x,y) ) { ... } Which could be implemented as : template <typename T> bool is_greater(const T& x, const T& y) { return x > y + Precision<T>::eps; }

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  • compiling boost based application using cron

    - by user303544
    Hi All, I am building some boost based application for various embedded targets. I have developed a script which can build my application with different toolchain for several targets. This script works fine when I run it from command line but if it is invoked from cron it always fails to link the object files. My application has dependency on openssl. Can anyone please give some idea? What would be the root cause of this kind of behavior? Thanks in advance.

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  • Adapting Map Iterators Using STL/Boost/Lambdas

    - by John Dibling
    Consider the following non-working code: typedef map<int, unsigned> mymap; mymap m; for( int i = 1; i < 5; ++i ) m[i] = i; // 'remove' all elements from map where .second < 3 remove(m.begin(), m.end(), bind2nd(less<int>(), 3)); I'm trying to remove elements from this map where .second < 3. This obviously isn't written correctly. How do I write this correctly using: Standard STL function objects & techniques Boost.Bind C++0x Lambdas I know I'm not eraseing the elements. Don't worry about that; I'm just simplifying the problem to solve.

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  • converting a timestring to a duration

    - by radman
    Hi, At the moment I am trying to read in a timestring formatted and create a duration from that. I am currently trying to use the boost date_time time_duration class to read and store the value. boost date_time provides a method time_duration duration_from_string(std::string) that allows a time_duration to be created from a time string and it accepts strings formatted appropriately ("[-]h[h][:mm][:ss][.fff]".). Now this method works fine if you use a correctly formatted time string. However if you submit something invalid like "ham_sandwich" or "100" then you will still be returned a time_duration that is not valid. Specifically if you try to pass it to a standard output stream then an assertion will occur. My question is: Does anyone know how to test the validity of the boost time_duration? and failing that can you suggest another method of reading a timestring and getting a duration from it? Note: I have tried the obvious testing methods that time_duration provides; is_not_a_date_time(), is_special() etc and they don't pick up that there is an issue. Using boost 1.38.0

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  • How to write a custom predicate for multi_index_containder with composite_key?

    - by Titan
    I googled and searched in the boost's man, but didn't find any examples. May be it's a stupid question...anyway. So we have the famous phonebook from the man: typedef multi_index_container< phonebook_entry, indexed_by< ordered_non_unique< composite_key< phonebook_entry, member<phonebook_entry,std::string,&phonebook_entry::family_name>, member<phonebook_entry,std::string,&phonebook_entry::given_name> >, composite_key_compare< std::less<std::string>, // family names sorted as by default std::greater<std::string> // given names reversed > >, ordered_unique< member<phonebook_entry,std::string,&phonebook_entry::phone_number> > > > phonebook; phonebook pb; ... // look for all Whites std::pair<phonebook::iterator,phonebook::iterator> p= pb.equal_range(boost::make_tuple("White"), my_custom_comp()); How should my_custom_comp() look like? I mean it's clear for me then it takes boost::multi_index::composite_key_result<CompositeKey> as an argumen (due to compilation errors :) ), but what is CompositeKey in that particular case? struct my_custom_comp { bool operator()( ?? boost::multi_index::composite_key_result<CompositeKey> ?? ) const { return blah_blah_blah; } }; Thanks in advance.

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  • Convert enumeration to string

    - by emptyheaded
    I am trying to build a function that converts an item from an enum to its corresponding string. The enums I use are fairly long, so I didn't want to use a switch-case. I found a method using boost::unordered_map very convenient, but I don't know how to make a default return (when there is no item matching the enum). const boost::unordered_map<enum_type, const std::string> enumToString = boost::assign::map_list_of (data_1, "data_1") (data_2, "data_2"); I tried to create an additional function: std::string convert(enum_type entry) { if (enumToString.find(entry)) // not sure what test to place here, return enumToString.at(entry); //because the find method returns an iter else return "invalid_value"; } I even tried something exceedingly wrong: std::string convert(enum_type entry) { try{ return enumToString.at(entry); } catch(...){ return "invalid_value"; } } Result: evil "Debug" runtime error. Can somebody give me a suggestion on how to either 1) find an easier method to convert enum to a string with the same name as the enum item 2) find a way to use already built boost methods to get a default value from a hash map (best option) 3) find what to place in the test to use a function that returns either the pair of the key-value, or a different string if the key is not found in the map. Thank you very much.

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  • is there a simple timed lock algorithm avoiding deadlock on multiple mutexes?

    - by Vicente Botet Escriba
    C++0x thread library or Boost.thread define a non-member variadic template function that locks all mutex at once that helps to avoid deadlock. template <class L1, class L2, class... L3> void lock(L1&, L2&, L3&...); The same can be applied to a non-member variadic template function try_lock_until, which locks all the mutex until a given time is reached that helps to avoid deadlock like lock(...). template <class Clock, class Duration, class L1, class L2, class... L3> void try_lock_until( const chrono::time_point<Clock,Duration>& abs_time, L1&, L2&, L3&...); I have an implementation that follows the same design as the Boost function boost::lock(...). But this is quite complex. As I can be missing something evident I wanted to know if: is there a simple timed lock algorithm avoiding deadlock on multiple mutexes? If no simple implementation exists, can this justify a proposal to Boost? P.S. Please avoid posting complex solutions.

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  • Work with function references

    - by Ockonal
    Hello, I have another one question about functions reference. For example, I have such definition: typedef boost::function<bool (Entity &handle)> behaviorRef; std::map< std::string, ptr_vector<behaviorRef> > eventAssociation; The first question is: how to insert values into such map object? I tried: eventAssociation.insert(std::pair< std::string, ptr_vector<behaviorRef> >(eventType, ptr_vector<behaviorRef>(callback))); But the error: no matching function for call to ‘boost::ptr_vector<boost::function<bool(Entity&)> >::push_back(Entity::behaviorRef&)’ And I undersatnd it, but can't make workable code. The second question is how to call such functions? For example, I have one object of behaviorRef, how to call it with boost::bind with passing my own values?

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  • WPF Databinding thread safety?

    - by Petoj
    Well lets say i have an object that i databind to, it implements INotifyPropertyChanged to tell the GUI when a value has changed... if i trigger this from a different thread than the GUI thread how would wpf behave? and will it make sure that it gets the value of the property from memory and not the cpu cache? more or less im asking if wpf does lock() on the object containing the property...

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