Yes. The OpenMP 4 target constructs were designed to support a wide range of accelerators. Compiler support for NVIDIA GPUs is available from GCC 7+ (see 1 and 2, although the latter has not been updated to reflect OpenMP 4 GPU support), Clang (see 3,4,5), and Cray. Compiler support for Intel GPUs is available in … Read more
In general, keep in mind that the directives and the functions are different things; the former are controlled by -fopenmp and the latter are controlled by linking to the OpenMP library. (Updated to incorporate comments) Try using the -fopenmp and -static options to statically link OpenMP. Because this implies -lgomp -lrt, the following command won’t … Read more
The gcc command in the latest Xcode suite is no longer the GCC frontend to LLVM (based on the very old GCC 4.2.1) but rather a symlink to clang. Clang does not (yet) support OpenMP. You have to install separately another version of GCC, e.g. by following this tutorial or by using any of the … Read more
You want the OMP_SET_LOCK/OMP_UNSET_LOCK functions: https://hpc.llnl.gov/tuts/openMP/#OMP_SET_LOCK Basically: omp_lock_t writelock; omp_init_lock(&writelock); #pragma omp parallel for for ( i = 0; i < x; i++ ) { // some stuff omp_set_lock(&writelock); // one thread at a time stuff omp_unset_lock(&writelock); // some stuff } omp_destroy_lock(&writelock); Most locking routines such as pthreads semaphores and sysv semaphores work on that … Read more
OpenMP is a set of code transforming pragmas, i.e. they are only applied at compile time. You cannot apply code transformation to an already compiled object code (ok, you can, but it is far more involving process and outside the scope of what most compilers do these days). You need -fopenmp during the link phase … Read more
On a Mac, the command gcc is a symlink to Clang. So by calling gcc -fopenmp -o your_program your_program.c you are in fact using Clang, which until now has not had built-in support for OpenMP. The newer versions of Clang do have support for OpenMP according to this post (where you can also find instructions … Read more
This command can help you brew install libomp brew info libomp libomp: stable 6.0.1 (bottled) LLVM’s OpenMP runtime library https://openmp.llvm.org/ /usr/local/Cellar/libomp/6.0.1 (12 files, 1.2MB) * Poured from bottle on 2018-11-20 at 16:12:22 From: https://github.com/Homebrew/homebrew-core/blob/master/Formula/libomp.rb ==> Dependencies Build: cmake ✘ ==> Requirements Required: macOS >= 10.10 ✔ ==> Caveats On Apple Clang, you need to add … Read more
You should make use of the OpenMP reduction clause for x and y: #pragma omp parallel for reduction(+:x,y) for (int j=0; j<n; j++) { double r=0.0; for (int i=0; i < m; i++){ double rand_g1 = cos(i/double(m)); double rand_g2 = sin(i/double(m)); x += rand_g1; y += rand_g2; r += sqrt(rand_g1*rand_g1 + rand_g2*rand_g2); } shifts[j] = … Read more
It seems to me as though the clock () function is calculating each thread’s individual time and adding up them up and displaying them. This is exactly what clock() does – it measures the CPU time used by the process, which at least on Linux and Mac OS X means the cumulative CPU time of … Read more
This appears to be a bug in gcc at least. The following code: #pragma GCC diagnostic ignored “-Wunknown-pragmas” #pragma GCC diagnostic ignored “-Wuninitialized” int fn(void) { #pragma xyzzy int x; return x; } int main (void) { return fn(); } has no problems ignoring the uninitialised x value but still complains about the pragma (without … Read more