Question

我已将KMP_AFFINITY设置为分散，但执行时间增加了很多！

这就是为什么我认为OpenMP只在1核上产生线程的原因。

所以我需要一些东西返回一个线程正在使用的核心。

这是我在for循环之前使用的pragma：

int procs = omp_get_num_procs();
#pragma omp parallel for num_threads(procs)\
shared (c, u, v, w, k, j, i, nx, ny) \
reduction(+: a, b, c, d, e, f, g, h, i)

这些是我做的出口：

export OMP_NUM_THREADS=5
export KMP_AFFINITY=verbose,scatter

如果它有助于我粘贴详细信息：

OMP: Info #149: KMP_AFFINITY: Affinity capable, using global cpuid instr info
OMP: Info #154: KMP_AFFINITY: Initial OS proc set respected: {0,1,2,3,4,5,6,7}
OMP: Info #156: KMP_AFFINITY: 8 available OS procs
OMP: Info #157: KMP_AFFINITY: Uniform topology
OMP: Info #159: KMP_AFFINITY: 2 packages x 4 cores/pkg x 1 threads/core (8 total cores)
OMP: Info #160: KMP_AFFINITY: OS proc to physical thread map ([] => level not in map):
OMP: Info #168: KMP_AFFINITY: OS proc 0 maps to package 0 core 0 [thread 0]
OMP: Info #168: KMP_AFFINITY: OS proc 4 maps to package 0 core 1 [thread 0]
OMP: Info #168: KMP_AFFINITY: OS proc 2 maps to package 0 core 2 [thread 0]
OMP: Info #168: KMP_AFFINITY: OS proc 6 maps to package 0 core 3 [thread 0]
OMP: Info #168: KMP_AFFINITY: OS proc 1 maps to package 1 core 0 [thread 0]
OMP: Info #168: KMP_AFFINITY: OS proc 5 maps to package 1 core 1 [thread 0]
OMP: Info #168: KMP_AFFINITY: OS proc 3 maps to package 1 core 2 [thread 0]
OMP: Info #168: KMP_AFFINITY: OS proc 7 maps to package 1 core 3 [thread 0]
OMP: Info #147: KMP_AFFINITY: Internal thread 0 bound to OS proc set {0}
OMP: Info #147: KMP_AFFINITY: Internal thread 1 bound to OS proc set {1}
OMP: Info #147: KMP_AFFINITY: Internal thread 2 bound to OS proc set {4}
OMP: Info #147: KMP_AFFINITY: Internal thread 3 bound to OS proc set {5}
OMP: Info #147: KMP_AFFINITY: Internal thread 4 bound to OS proc set {2}
OMP: Info #147: KMP_AFFINITY: Internal thread 5 bound to OS proc set {3}
OMP: Info #147: KMP_AFFINITY: Internal thread 6 bound to OS proc set {6}
OMP: Info #147: KMP_AFFINITY: Internal thread 7 bound to OS proc set {7}

提前感谢！

Answer 1

作为@ user3018144 pointed out，sched_getcpu(3)可用于获取CPU编号。

请考虑以下代码：

#define _GNU_SOURCE // sched_getcpu(3) is glibc-specific (see the man page)

#include <stdio.h>
#include <sched.h>
#include <omp.h>

int main() {
#pragma omp parallel
    {
        int thread_num = omp_get_thread_num();
        int cpu_num = sched_getcpu();
        printf("Thread %3d is running on CPU %3d\n", thread_num, cpu_num);
    }

    return 0;
}

这是我没有亲和力的输出：

$> OMP_NUM_THREADS=4 ./a.out | sort
Thread   0 is running on CPU   2
Thread   1 is running on CPU   0
Thread   2 is running on CPU   3
Thread   3 is running on CPU   1

这是具有亲和力的输出：

$> GOMP_CPU_AFFINITY='0,1,2,3' OMP_NUM_THREADS=4 ./a.out | sort
Thread   0 is running on CPU   0
Thread   1 is running on CPU   1
Thread   2 is running on CPU   2
Thread   3 is running on CPU   3

Answer 2

如果您使用的是Linux，则可以使用函数sched_getcpu()。这是一个解释它是如何工作的链接及其声明：

http://man7.org/linux/man-pages/man3/sched_getcpu.3.html

希望这可以提供帮助

OpenMP的。如何检索线程正在运行的核心ID

2 个答案: