OpenMP：当代码以普通用户身份运行时，“libgomp：线程创建失败：资源暂时不可用”

Question

当我运行以下示例代码时：

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

int main(int argc, char *argv[])
{
  #pragma omp parallel
  {
   int NCPU,tid,NPR,NTHR;
    /* get the total number of CPUs/cores available for OpenMP */
   NCPU = omp_get_num_procs();
   /* get the current thread ID in the parallel region */
   tid = omp_get_thread_num();
   /* get the total number of threads available in this parallel region */
   NPR = omp_get_num_threads();
   /* get the total number of threads requested */
   NTHR = omp_get_max_threads();
   /* only execute this on the master thread! */

   if (tid == 0) {
     printf("%i : NCPU\t= %i\n",tid,NCPU);
     printf("%i : NTHR\t= %i\n",tid,NTHR);
     printf("%i : NPR\t= %i\n",tid,NPR);
   }
   printf("%i : hello multicore user! I am thread %i out of %i\n",tid,tid,NPR);
  }
  return(0);
 }

使用命令：gcc -fopenmp example.c -o example.exe然后./example我收到错误：libgomp: Thread creation failed: Resource temporarily unavailable但是，当我在下面运行相同的代码和命令时，sudo我得到了预期的输出：

0 : NCPU    = 4
0 : NTHR    = 4
0 : NPR = 4
2 : hello multicore user! I am thread 2 out of 4
1 : hello multicore user! I am thread 1 out of 4
0 : hello multicore user! I am thread 0 out of 4
3 : hello multicore user! I am thread 3 out of 4

我在 4 核 x86_64 架构上运行 Ubuntu 18.04。

Architecture:        x86_64
CPU op-mode(s):      32-bit, 64-bit
Byte Order:          Little Endian
CPU(s):              4
On-line CPU(s) list: 0-3
Thread(s) per core:  2
Core(s) per socket:  2
Socket(s):           1
NUMA node(s):        1
Vendor ID:           GenuineIntel
CPU family:          6
Model:               78
Model name:          Intel(R) Core(TM) i5-6200U CPU @ 2.30GHz

我真的不太舒服以 root 用户身份使用 Openmp 运行 c 代码。我的问题是，有人可以提供有关为什么会发生这种情况的信息吗？谢谢

Answer 1

修复错误：

"libgomp: Thread creation failed: Resource temporarily unavailable"

特别是在只有1个CPU的系统中，只需要减少线程：

export OMP_NUM_THREADS=1

继续....