https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109875
Bug ID: 109875 Summary: [OpenMP] nteams-var / OMP_NUM_TEAMS → ICV not passed to the device / default value Product: gcc Version: 13.0 Status: UNCONFIRMED Keywords: openmp Severity: normal Priority: P3 Component: libgomp Assignee: unassigned at gcc dot gnu.org Reporter: burnus at gcc dot gnu.org CC: jakub at gcc dot gnu.org Target Milestone: --- Related: https://github.com/SOLLVE/sollve_vv/pull/728 and OpenMP Spec Issue 3619. The following is with host fallback - and I might miss something because of this. However, I get only a single team with the following code; even though max_num_teams == 3. Replacing the set_num_teams by OMP_NUM_TEAMS=7 OMP_NUM_TEAMS_DEV=8 will yield the expected 7 for max_teams. But it will still execute with a single team. — Using num_teams(3) as clause will have an effect, however. TODO: * Check whether TEAMS = 1 makes sense for host fallback and what the result is with actual offloading. EXPECTED: * The value of the ICV is honored on the device side * Possibly, the initial value should be not 0 but a different value, but that depends on the OpenMP Spec Issue 3619. NOTE: While the init value is now changed, as omp_get_max_teams() is confusingly written, just changing the default is undetectable inside the program as only omp_get_max_teams() or display-env can be used to determine the value - and the values returned by the latter is not really available for consumption inside of the program. * On the host side, the default seems to be 3, given that there is: libgomp/teams.c: num_teams = gomp_nteams_var ? gomp_nteams_var : 3; It seems as if get_gomp_offload_icvs sets the ICV for the device but it does not seem to get actually get used. – At least not for host fallback. #include <omp.h> int main () { int num_teams; #if 1 // set to 0 to test the environment variables omp_set_num_teams(2); #pragma omp target omp_set_num_teams(3); #endif __builtin_printf("max_teams: %d\n", omp_get_max_teams()); #pragma omp target teams map(tofrom: num_teams) //num_teams(4) { if (omp_get_team_num() == 0) { num_teams = omp_get_num_teams(); } } __builtin_printf("num_teams: %d\n", num_teams); return 0; }