m4/ax_check_openmp.m4

   1 # Check if $CC supports openmp.
   2 AC_DEFUN([AX_CHECK_OPENMP], [
   3         AC_SUBST(HAVE_OPENMP)
   4         HAVE_OPENMP=no
   5         AC_MSG_CHECKING([for OpenMP support by $CC])
   6         echo | $CC -x c - -fsyntax-only -fopenmp -Werror >/dev/null 2>/dev/null
   7         if test $? -eq 0; then
   8                 HAVE_OPENMP=yes
   9         fi
  10         AC_MSG_RESULT($HAVE_OPENMP)
  11
  12         if test $HAVE_OPENMP = yes; then
  13                 SAVE_CFLAGS=$CFLAGS
  14                 CFLAGS="$CFLAGS -fopenmp"
  15                 # Using some version of clang, the value of "m" becomes zero
  16                 # after the parallel for loop.
  17                 AC_RUN_IFELSE([AC_LANG_PROGRAM([[
  18                 #include <stdlib.h>
  19
  20                 static void f(int m, double A[m])
  21                 {
  22                         #pragma omp parallel for
  23                         for (int c0 = 0; c0 < m; c0 += 1)
  24                                 A[c0] = 0.;
  25                         if (m != 100)
  26                                 abort();
  27                 }
  28                 ]],[[
  29                 double A[100];
  30
  31                 f(100, A);
  32                 ]])],[],[
  33                         AC_MSG_NOTICE([OpenMP support broken, disabling])
  34                         HAVE_OPENMP=no
  35                 ],[])
  36                 CFLAGS=$SAVE_CFLAGS
  37         fi
  38 ])