在Mac OS X(Sierra& amp; Mojave)的clang中启用OpenMP支持 [英] Enable OpenMP support in clang in Mac OS X (sierra & Mojave)

问题描述

我使用的是Mac OS X Sierra，我发现clang(LLVM版本8.1.0(clang-802.0.38))不支持OpenMP:当我运行 clang -fopenmp program_name.c 时，出现以下错误:

I am using Mac OS X Sierra, and I found that clang (LLVM version 8.1.0 (clang-802.0.38)) does not support OpenMP: when I run clang -fopenmp program_name.c, I got the following error:

clang: 错误:不支持的选项-fopenmp"

似乎clang不支持 -fopenmp 标志.

It seems that clang does not support -fopenmp flag.

我在自制软件中找不到任何openmp库.根据LLVM网站，LLVM已经支持OpenMP.但是我找不到在编译过程中启用它的方法.

I could not find any openmp library in homebrew. According to LLVM website, LLVM already supports OpenMP. But I could not find a way to enable it during compiling.

这是否意味着Mac中的默认clang不支持OpenMP?您能提供任何建议吗?

Does this mean that the default clang in Mac does not support OpenMP? Could you provide any suggestions?

(当我切换到GCC来编译同一程序时(使用 brew install gcc --without-multilib 安装gcc)，并且编译成功.)

(When I switch to GCC to compile the same program (gcc is installed using brew install gcc --without-multilib), and the compilation is successful.)

推荐答案

尝试使用 Homebrew 的llvm:

Try using Homebrew's llvm:

brew install llvm

然后，您将所有llvm二进制文件保存在/usr/local/opt/llvm/bin 中.例如，要编译 OpenMP Hello World程序，请键入

You then have all the llvm binaries in /usr/local/opt/llvm/bin. To compile the OpenMP Hello World program, for example, type

/usr/local/opt/llvm/bin/clang -fopenmp -L/usr/local/opt/llvm/lib omp_hello.c -o hello

您可能还必须使用 -I/usr/local/opt/llvm/include 设置 CPPFLAGS .

You might also have to set the CPPFLAGS with -I/usr/local/opt/llvm/include.

makefile应该如下所示:

A makefile should look like this:

CPP = /usr/local/opt/llvm/bin/clang
CPPFLAGS = -I/usr/local/opt/llvm/include -fopenmp
LDFLAGS = -L/usr/local/opt/llvm/lib

omp_hello: omp_hello.c
    $(CPP) $(CPPFLAGS) $^ -o $@ $(LDFLAGS)

更新:在macOS 10.14(Mojave)中，您可能会收到类似错误

Update: In macOS 10.14 (Mojave) you might get an error like

/usr/local/Cellar/llvm/7.0.1/lib/clang/7.0.1/include/omp.h:118:13: fatal error: 'stdlib.h' file not found

如果发生这种情况，则/usr/include 中缺少macOS SDK标头.他们使用 Xcode 10 进入了SDK本身.使用

If this happens, the macOS SDK headers are missing from /usr/include. They moved into the SDK itself with Xcode 10. Install the headers into /usr/include with

open /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg

更新2:样本文件 omp_hello.c 似乎已从上面的直接链接中删除，所以它是:

Update 2: The sample file omp_hello.c seems to be gone from the direct link above, so here it is:

/******************************************************************************
* FILE: omp_hello.c
* DESCRIPTION:
*   OpenMP Example - Hello World - C/C++ Version
*   In this simple example, the master thread forks a parallel region.
*   All threads in the team obtain their unique thread number and print it.
*   The master thread only prints the total number of threads.  Two OpenMP
*   library routines are used to obtain the number of threads and each
*   thread's number.
* AUTHOR: Blaise Barney  5/99
* LAST REVISED: 04/06/05
******************************************************************************/
#include <omp.h>
#include <stdio.h>
#include <stdlib.h>

int main (int argc, char *argv[]) 
{
int nthreads, tid;

/* Fork a team of threads giving them their own copies of variables */
#pragma omp parallel private(nthreads, tid)
  {

  /* Obtain thread number */
  tid = omp_get_thread_num();
  printf("Hello World from thread = %d\n", tid);

  /* Only master thread does this */
  if (tid == 0) 
    {
    nthreads = omp_get_num_threads();
    printf("Number of threads = %d\n", nthreads);
    }

  }  /* All threads join master thread and disband */

}

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