-fopenmp提供什么预处理程序定义? [英] What preprocessor define does -fopenmp provide?

问题描述

我有一些可以与OpenMP一起运行(或不与OpenMP一起运行)的代码-这取决于用户如何设置Makefile.如果他们想与OpenMP一起运行，则只需将-fopenmp添加到CFLAGS和CXXFLAGS.

我正在尝试确定可以使用什么预处理器宏来告知-fopenmp何时生效. omp.h标头看起来不太有趣:

 $ cat /usr/lib/gcc/x86_64-linux-gnu/4.8/include/omp.h | grep define
#define OMP_H 1
#define _LIBGOMP_OMP_LOCK_DEFINED 1
# define __GOMP_NOTHROW throw ()
# define __GOMP_NOTHROW __attribute__((__nothrow__))
 

而且我无法让预处理器提供任何有用的东西:

 $ cpp -dM -fopenmp </dev/null | grep -i omp
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1 1
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2 1
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 1
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8 1
#define __STDC_IEC_559_COMPLEX__ 1

$ cpp -dM -fopenmp </dev/null | grep -i version
#define __GXX_ABI_VERSION 1002
#define __VERSION__ "4.8.2"
 

-fopenmp提供什么预处理程序定义?

---

这类似于如何确定OpenMP是否正在工作?但是我对编译时感兴趣，而不是在编译时感兴趣构建后或运行时.

注意 :该项目不使用Boost，不使用Autotools，也不使用Cmake.它只使用一个makefile.

解决方案

您的grep过于具体，您应该寻找"openmp".

或者，将cpp -dM -fopenmp </dev/null和cpp -dM </dev/null进行比较会产生一个差异:

#define _OPENMP 201107

应该正是您要寻找的.

I've got some code that can run with (or without) OpenMP - it depends on how the user sets up the makefile. If they want to run with OpenMP, then they just add -fopenmp to CFLAGS and CXXFLAGS.

I'm trying to determine what preprocessor macro I can use to tell when -fopenmp is in effect. The omp.h header does not look very interesting:

$ cat /usr/lib/gcc/x86_64-linux-gnu/4.8/include/omp.h | grep define
#define OMP_H 1
#define _LIBGOMP_OMP_LOCK_DEFINED 1
# define __GOMP_NOTHROW throw ()
# define __GOMP_NOTHROW __attribute__((__nothrow__))

And I can't get the preprocessor to offer up anything useful:

$ cpp -dM -fopenmp </dev/null | grep -i omp
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1 1
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2 1
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 1
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8 1
#define __STDC_IEC_559_COMPLEX__ 1

$ cpp -dM -fopenmp </dev/null | grep -i version
#define __GXX_ABI_VERSION 1002
#define __VERSION__ "4.8.2"

What preprocessor define does -fopenmp provide?

---

This is similar to How to tell if OpenMP is working? But I'm interested in compile time, and not post-build or runtime.

Note: this project does not use Boost, does not use Autotools, and does not use Cmake. It just uses a makefile.

解决方案

Your grep was overly specific, you should have looked for "openmp".

Or rather, diffing cpp -dM -fopenmp </dev/null and cpp -dM </dev/null produces a single diff:

#define _OPENMP 201107

Which should be exactly what you are looking for.

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