https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98699
Bug ID: 98699
Summary: Reset OMP_NESTED to true if OMP_MAX_ACTIVE_LEVELS is >
1.
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: longb at cray dot com
Target Milestone: ---
The user's desire is that, for an OpenMP code, if the maximum number
of active levels (OMP_MAX_ACTIVE_LEVELS) has a value greater than 1
then the internal variable for nesting (OMP_NESTING) automatically be
reset to .true. . The Cray and Intel compilers appear to do this (and
issue a message about OMP_NESTING being deprecated) while gfortran
does not. If NESTING is disabled, having the maximum number of active
levels greater than 1 does not seem to make sense.
Simple test code:
> cat test.f90
program list_omp_internan_vars
use omp_lib
integer active
logical nested
nested = omp_get_nested()
print *, "Internal value for omp_nested is ", nested
active = omp_get_max_active_levels()
print *, "Internal value for omp_max_active_levels is ", active
end program list_omp_internan_vars
For gfortran:
> gfortran -fopenmp test.f90
> export OMP_MAX_ACTIVE_LEVELS=1
> srun -n1 -c4 ./a.out
Internal value for omp_nested is F
Internal value for omp_max_active_levels is 1
> export OMP_MAX_ACTIVE_LEVELS=4
> srun -n1 -c4 ./a.out
Internal value for omp_nested is F
Internal value for omp_max_active_levels is 4
> gfortran --version
GNU Fortran (GCC) 10.2.0 20200723 (Cray Inc.)
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Same example with CCE:
> ftn -homp test.f90
> export OMP_MAX_ACTIVE_LEVELS=1
> srun -n1 -c4 ./a.out
WARNING: omp_get_nested has been deprecated in OpenMP 5.0.
Internal value for omp_nested is F
Internal value for omp_max_active_levels is 1
> export OMP_MAX_ACTIVE_LEVELS=4
srun -n1 -c4 ./a.out
WARNING: omp_get_nested has been deprecated in OpenMP 5.0.
Internal value for omp_nested is T
Internal value for omp_max_active_levels is 4
Same example with Intel ( same convention as the Cray compiler):
> export OMP_MAX_ACTIVE_LEVELS=1
> ifort -qopenmp test.f90
> srun -n1 -c4 ./a.out
OMP: Info #274: omp_get_nested routine deprecated, please use
omp_get_max_active_levels instead.
Internal value for omp_nested is F
Internal value for omp_max_active_levels is 1
> export OMP_MAX_ACTIVE_LEVELS=4
> srun -n1 -c4 ./a.out
OMP: Info #274: omp_get_nested routine deprecated, please use
omp_get_max_active_levels instead.
Internal value for omp_nested is T
Internal value for omp_max_active_levels is 4
