How to check the version of OpenMP on Linux

Question

I wonder how to check the version of OpenMP on a Linux remote machine?

I don't know where it is installed either.

Answer 1

Here's a short C++11 program to display your OpenMP version; it also covers version 4.5 which was released in November 2015.

#include <unordered_map>
#include <cstdio>
#include <omp.h>

int main(int argc, char *argv[])
{
  std::unordered_map<unsigned,std::string> map{
    {200505,"2.5"},{200805,"3.0"},{201107,"3.1"},{201307,"4.0"},{201511,"4.5"}};
  printf("We have OpenMP %s.\n", map.at(_OPENMP).c_str());
  return 0;
}

and compile it with:

g++ -std=c++11 -fopenmp foobar.cpp

Answer 2

It appears that the C/C++ specification for OpenMP provides no direct way of doing this programmatically. So you have to check the docs for your compiler version.

gcc --version ## get compiler version

For GCC, this is a good resource (does not mention newest versions of GCC): http://gcc.gnu.org/wiki/openmp:

As of GCC 4.2, the compiler implements version 2.5 of the OpenMP standard and as of 4.4 it implements version 3.0 of the OpenMP standard. The OpenMP 3.1 is supported since GCC 4.7.

---

Edit

After trying a bit harder, I got the following to work. It at least gives an indication of the OpenMP version -- although it still requires you to look something up.

$ echo |cpp -fopenmp -dM |grep -i open
#define _OPENMP 200805

You can go here (http://www.openmp.org/specifications/) to discover the mapping between the date provided and the actual OpenMP version number.

In implementations that support a preprocessor, the _OPENMP macro name is defined to have the decimal value yyyymm where yyyy and mm are the year and month designations of the version of the OpenMP API that the implementation supports.

Answer 3

You need to check your gcc version using

gcc --version

and then see the (incomplete) table below (whose info is gathered from this Wiki article and from this webpage from the OpenMP official website):

| gcc version | OpenMP version |    Languages    | Offloading |
|-------------|----------------|-----------------|------------|
|    4.2.0    |       2.5      |        C        |            |
|    4.4.0    |       3.0      |        C        |            |
|    4.7.0    |       3.1      |        C        |            |
|    4.9.0    |       4.0      |      C, C++     |            |
|    4.9.1    |       4.0      | C, C++, Fortran |            |
|      5      |                |                 |     Yes    |
|     6.1     |       4.5      |      C, C++     |            |

The blank entries are there because I didn't find the corresponding info.

Answer 4

First set environment variable OMP_DISPLAY_ENV: in bash:

export  OMP_DISPLAY_ENV="TRUE" 

or in csh-like shell:

setenv OMP_DISPLAY_ENV TRUE

Then compile and run your OpenMP program:

./a.out

There will be additional info, like :

OPENMP DISPLAY ENVIRONMENT BEGIN
  _OPENMP = '201511'
  OMP_DYNAMIC = 'FALSE'
  OMP_NESTED = 'FALSE'
  OMP_NUM_THREADS = '8'
  OMP_SCHEDULE = 'DYNAMIC'
  OMP_PROC_BIND = 'FALSE'
  OMP_PLACES = ''
  OMP_STACKSIZE = '0'
  OMP_WAIT_POLICY = 'PASSIVE'
  OMP_THREAD_LIMIT = '4294967295'
  OMP_MAX_ACTIVE_LEVELS = '2147483647'
  OMP_CANCELLATION = 'FALSE'
  OMP_DEFAULT_DEVICE = '0'
  OMP_MAX_TASK_PRIORITY = '0'
OPENMP DISPLAY ENVIRONMENT END

where _OPENMP have the 8 decimal value yyyymm where yyyy and mm are the year and month designations of the version of the OpenMP API that the implementation supports.