openmp

问题 I have a few questions about using common blocks in parallel programming in Fortran. My subroutines have common blocks. Do I have to declare all the common blocks and threadprivate in the parallel do region? How do they pass information? I want seperate common clock for each thread and want them to pass information through the end of parallel region. Does it happen here? My Ford subroutine changes some variables in common blocks and Condact subroutine overwrites over them again but the

问题 I am attempting to speed up this for loop with OpenMP parallelization. I was under the impression that this should split up the work across a number of threads. However, perhaps the overhead is too large for this to give me any speedup. I should mention that this loop occurs many many many times, and each instance of the loop should be parallelized. The number of loop iterations, newNx, can be as small as 3 or as large as 256. However, if I conditionally have it parallelized only for newNx >

问题 I am trying to parallelize a program using openmp on a Mac, but I can not manage to make it multi-threaded. I've tried building llvm/clang/openmp 3.7.1 from source (after a svn co) as documented, I have also tried using the prebuild versions of clang and OpenMP 3.7.0 given by the llvm project. In each case, the resulting compiler works fine with the -fopenmp flag and produce an executable that links to the openmp runtime. I use the following openmp 'hello world' program: #include <omp.h>

问题 I am trying to parallelize a program using openmp on a Mac, but I can not manage to make it multi-threaded. I've tried building llvm/clang/openmp 3.7.1 from source (after a svn co) as documented, I have also tried using the prebuild versions of clang and OpenMP 3.7.0 given by the llvm project. In each case, the resulting compiler works fine with the -fopenmp flag and produce an executable that links to the openmp runtime. I use the following openmp 'hello world' program: #include <omp.h>

问题 I've done some searching but couldn't find anything that appeared to be related to my question (sorry if my question is redundant!). Anyway, as the title states, I'm having trouble getting any improvement over the serial implementation of my code. The code snippet that I need to parallelize is as follows (this is Fortran90 with OpenMP): do n=1,lm do m=1,jm do l=1,im sum_u = 0 sum_v = 0 sum_t = 0 do k=1,lm !$omp parallel do reduction (+:sum_u,sum_v,sum_t) do j=1,jm do i=1,im exp_smoother=exp(-

问题 I want to start to write applications(C++) that will utilize the additional cores to execute portions of the code that have a need to perform lots of calculations and whose computations are independent of each other. I have the following processor : x64 Family 15 Model 104 Stepping 2 Authentic AMD ~1900 Mhz running on Windows Vista Home premium 32 bit and Opensuse 11.0 64 bit. On the Intel platforms , I've used the following APIs Intel TBB, OpenMP. Do they work on AMD and does AMD have

问题 I want to start to write applications(C++) that will utilize the additional cores to execute portions of the code that have a need to perform lots of calculations and whose computations are independent of each other. I have the following processor : x64 Family 15 Model 104 Stepping 2 Authentic AMD ~1900 Mhz running on Windows Vista Home premium 32 bit and Opensuse 11.0 64 bit. On the Intel platforms , I've used the following APIs Intel TBB, OpenMP. Do they work on AMD and does AMD have

问题 Please look at this code. Single-threaded program: http://pastebin.com/KAx4RmSJ. Compiled with: g++ -lrt -O2 main.cpp -o nnlv2 Multithread with openMP: http://pastebin.com/fbe4gZSn Compiled with: g++ -lrt -fopenmp -O2 main_openmp.cpp -o nnlv2_openmp I tested it on a dual core system (so we have two threads running in parallel). But multi-threaded version is slower than the single-threaded one (and shows unstable time, try to run it few times). What's wrong? Where did I make mistake? Some

问题 Is there a function or any other way to know, programatically, what core of what processor a given thread of my program (pid) is running on? Both OpenMP or Pthreads solutions would help me, if possible. Thanks. 回答1: This is going to be platform-specific, I would think. On Windows you can use NtGetCurrentProcessorNumber, but this is caveat-ed as possibly disappearing. I expect this is hard to do, because there's nothing to stop the thread being moved to a new core at any time (in most apps,

问题 I have been working on making my code able to be auto vectorised by GCC, however, when I include the the -fopenmp flag it seems to stop all attempts at auto vectorisation. I am using the ftree-vectorize -ftree-vectorizer-verbose=5 to vectorise and monitor it. If I do not include the flag, it starts to give me a lot of information about each loop, if it is vectorised and why not. The compiler stops when I try to use the omp_get_wtime() function, since it can't be linked. Once the flag is