openmp

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I am using OpenMP in my Visual Studio projects and currently thinking very seriously in changing to QT creator. (Doesn't Visual Studio suck?,I expect much more from Microsoft) But anyway... Does QT creator support OpenMP? In case of that, what should I do to enable it? Or maybe is enabled by default? Do I need to do something special? Thanks for your advices. Ignacio. 回答1: Does QT creator support OpenMP? As someone else mentioned, it's not Qt itself that support OpenMP but the compiler. What should I do to enable it? If you have installed a

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: main program: program main use omp_lib use my_module implicit none integer, parameter :: nmax = 202000 real(8) :: e_in(nmax) = 0.D0 integer i call omp_set_num_threads(2) !$omp parallel default(firstprivate) !$omp do do i=1,2 print *, e_in(i) print *, eTDSE(i) end do !$omp end do !$omp end parallel end program main module: module my_module implicit none integer, parameter, private :: ntmax = 202000 double complex :: eTDSE(ntmax) = (0.D0,0.D0) !$omp threadprivate(eTDSE) end module my_module compiled using: ifort -openmp main.f90 my_module.f90

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: In the following example the C++11 threads take about 50 seconds to execute, but the OMP threads only 5 seconds. Any ideas why? (I can assure you it still holds true if you are doing real work instead of doNothing , or if you do it in a different order, etc.) I'm on a 16 core machine, too. #include <iostream> #include <omp.h> #include <chrono> #include <vector> #include <thread> using namespace std; void doNothing() {} int run(int algorithmToRun) { auto startTime = std::chrono::system_clock::now(); for(int j=1; j<100000; ++j) { if

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I am new to OpenMP. I want to solve a stiff ODE system for a range of parameter values using parallel do loops. I use the following code in Fortran given below. However, I do not know whether calling a stiff solver(as a subroutine) inside a parallel do loop is allowed or not? Also, I want to write the time series data into files with filenames such as "r_value_s__value.txt" in the subroutine before the return to the main program. Can anyone help. Below is the code and the error. I used gfortran with flags -fopenmp to compile. PROGRAM OPENMP

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: I try to compile #include <omp.h> using namespace std ; vector < vector <int> > multiplyMatrixes ( const vector < vector <int> > & a , const vector < vector <int> > & b , int aHeight , int aWidth , int bHeight , int bWidth ) { vector < vector <int> > c ( aHeight , vector <int> ( bWidth , 0 )); #pragma omp parallel for collapse ( 2 ) for ( int row = 0 ; row < aHeight ; row ++) { for ( int col = 0 ; col < bWidth ; col ++) { int value = 0 ; for ( int i = 0 ; i < aWidth ; i ++) { value += a [ row ][ i ] * b [ i ][ col ]; } c [ row ][

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I am trying to parallelize a large program that is written by a third-party. I cannot disclose the code, but I will try and give the closest example of what I wish to do. Based on the code below. As you can see, since the clause "parallel" is INSIDE the while loop, the creation/destruction of the threads are(is) done with each iteration, which is costly. Given that I cannot move the Initializors...etc to be outside the "while" loop. --Base code void funcPiece0() { // many lines and branches of code } void funcPiece1() { // also many lines

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: I am aware that VC2010 Express Edition does not include OpenMP support and therefore would report omp.h file missing. Therefore, I have installed Windows SDK v7.1 64-bit version in Windows. However, even I ran: set DISTUTIL_USE_SDK = 1 setenv / x64 / release And then try to compile the code, it would still report cannot find omp.h. Could anyone give me a hint on how to solve this? 回答1: Did some checking, and it appears that OpenMP is not part of the Windows SDK, and is only shipped with Visual C++ 2010 Professional or Ultimate

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: I was trying to compiled the following code: #pragma omp parallel shared ( j ) { #pragma omp for schedule ( dynamic ) for ( i = 0 ; i != j ; i ++) { // do something } } I get this error: error: invalid controlling predicate . I check the openMP reference guide and it says that for the parallel for it "only" allows one of the following operators: < <= > >=. I don't understand why not allow i != j . I could understand if it was the static schedule, since openMP need to pre-compute the number of iterations assigned to each thread. But

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: Is there any counter-indication to doing this ? Or is the behavior well specified? #pragma omp parallel for for(auto x : stl_container) { ... } Because it seems that OpenMP specification is only valid for c++98 but I guess there might be more incompatibilities due to C++11 threads, which are not used here. I wanted to be sure, still. 回答1: The OpenMP 4.0 specification was finalised and published several days ago here . It still mandates that parallel loops should be in the canonical form (§2.6, p.51): for ( init-expr ; test-expr ; incr-expr )

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: Will sched_setaffinity or pthread_attr_setaffinity_np work to set thread affinity under OpenMP? Related: CPU Affinity 回答1: Yes, named calls will work to set thread affinity. The only problem is to fix thread number and to set right affinity in right thread (you can try using static scheduling of for loop for known number of threads). As I know, almost every openmp allows to set affinity via environment. The name of environment variable varies (it was not standartized some time ago). I use http://www.spec.org/omp2001/results/omp2001.html page