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This macro tries to find out how to compile programs that use OpenMP a standard API and set of compiler directives for parallel programming (see http://www-unix.mcs/)

On success, it sets the OPENMP_CFLAGS/OPENMP_CXXFLAGS/OPENMP_F77FLAGS output variable to the flag (e.g. -omp) used both to compile *and* link OpenMP programs in the current language.

NOTE: You are assumed to not only compile your program with these flags, but also link it with them as well.

If you want to compile everything with OpenMP, you should set:


(depending on the selected language).

The user can override the default choice by setting the corresponding environment variable (e.g. OPENMP_CFLAGS).

ACTION-IF-FOUND is a list of shell commands to run if an OpenMP flag is found, and ACTION-IF-NOT-FOUND is a list of commands to run it if it is not found. If ACTION-IF-FOUND is not specified, the default action will define HAVE_OPENMP.

Source Code

Download the latest version of ax_openmp.m4 or browse the macro’s revision history.


Copyright © 2008 Steven G. Johnson
Copyright © 2015 John W. Peterson
Copyright © 2016 Nick R. Papior

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see <>.

As a special exception, the respective Autoconf Macro’s copyright owner gives unlimited permission to copy, distribute and modify the configure scripts that are the output of Autoconf when processing the Macro. You need not follow the terms of the GNU General Public License when using or distributing such scripts, even though portions of the text of the Macro appear in them. The GNU General Public License (GPL) does govern all other use of the material that constitutes the Autoconf Macro.

This special exception to the GPL applies to versions of the Autoconf Macro released by the Autoconf Archive. When you make and distribute a modified version of the Autoconf Macro, you may extend this special exception to the GPL to apply to your modified version as well.

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