Question

我安装了gcc-7，gcc-8，gcc-7-offload-nvptx和gcc-8-offload-nvptx

我尝试用两者编译一个简单的OpenMP代码并卸载：

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

int main(){
    #pragma omp target
    #pragma omp teams distribute parallel for
    for (int i=0; i<omp_get_num_threads(); i++)
        printf("%d in %d of %d\n",i,omp_get_thread_num(), omp_get_num_threads());
}

使用以下行（也gcc-7）：

gcc-8 code.c -fopenmp -foffload=nvptx-none

但它没有编译，给出以下错误：

/tmp/ccKESWcF.o: In function "main":
teste.c:(.text+0x50): undefined reference to "GOMP_target_ext"
/tmp/cc0iOH1Y.target.o: In function "init":
ccPXyu6Y.c:(.text+0x1d): undefined reference to "GOMP_offload_register_ver"
/tmp/cc0iOH1Y.target.o: In function "fini":
ccPXyu6Y.c:(.text+0x41): undefined reference to "GOMP_offload_unregister_ver"
collect2: error: ld returned 1 exit status

一些线索？

Answer 1

您使用-foffload=disable -fno-stack-protector和gcc7以及Ubuntu 17.10，使用gcc-7-offload-nvptx编码并运行代码。

但是在GPU上（没有-foffload=disable）它无法编译。您无法从GPU调用printf。相反，你可以这样做：

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

int main(){
  int nthreads;
  #pragma omp target teams map(tofrom:nthreads)
  #pragma omp parallel
  #pragma omp single
  nthreads = omp_get_num_threads();

  int *ithreads = malloc(sizeof *ithreads *nthreads);

  #pragma omp target teams distribute parallel for map(tofrom:ithreads[0:nthreads])
  for (int i=0; i<nthreads; i++) ithreads[i] = omp_get_thread_num();

  for (int i=0; i<nthreads; i++)
    printf("%d in %d of %d\n", i, ithreads[i], nthreads);

  free(ithreads);  
}

对我来说这是输出

0 in 0 of 8
1 in 0 of 8
2 in 0 of 8
3 in 0 of 8
4 in 0 of 8
5 in 0 of 8
6 in 0 of 8
7 in 0 of 8

在OpenMP卸载到nvptx时gcc 7和8（debian）的问题

1 个答案: