Fixes are available
APAR status
Closed as program error.
Error description
The following test case produces incorrect output for OMP_SCHEDULE=DYNAMIC and OMP_SCHEDULE=GUIDED. $cat workshare.f90 program workshare !$ use OMP_LIB implicit none integer, parameter :: n=100 integer :: i, j, num_th real(kind=8), dimension(n,n) :: a !$ integer :: nb_taches !$OMP PARALLEL !$ nb_taches = OMP_GET_NUM_THREADS() !$OMP END PARALLEL !$ print '(3X,"Parallel execution with ",i2," threads")',nb_taches a(:,:)=1 !$OMP PARALLEL PRIVATE(num_th) !$ num_th= OMP_GET_THREAD_NUM() !$OMP WORKSHARE forall (i=2:n, j=1:n-1, i>j) a(j,i) = a(i,j) forall (i=1:n) a(i,i) = a(i,i) + 800.0_8 !$OMP END WORKSHARE if (num_th == 0) print*,"Sum = ",sum(a) !$OMP END PARALLEL end program workshare $cat submit.sh cd ./ make all echo Monoprocessor echo ./workshare_mono.exe echo echo OMP_SCHEDULE=STATIC export OMP_SCHEDULE="STATIC" ./workshare_omp.exe echo echo OMP_SCHEDULE=DYNAMIC export OMP_SCHEDULE="DYNAMIC" ./workshare_omp.exe echo echo OMP_SCHEDULE=GUIDED export OMP_SCHEDULE="GUIDED" ./workshare_omp.exe echo echo The END. $cat Makefile FC =xlf90_r LDFLAGS = OMP = -qsmp=omp CMD = workshare SRC = workshare.f90 OBJ = workshare.o FFLAGS = -qfree=f90 -O3 all: mono para mono: $(FC) $(FFLAGS) -c $(SRC) $(FC) $(LDFLAGS) $(OBJ) -o $(CMD)_mono.exe para: $(FC) $(FFLAGS) $(OMP) -c $(SRC) $(FC) $(LDFLAGS) $(OMP) $(OBJ) -o $(CMD)_omp.exe clean: rm *.o *.exe $./submit.sh Monoprocessor Sum = 90000.0000000000000 OMP_SCHEDULE=STATIC Parallel execution with 4 threads Sum = 90000.0000000000000 OMP_SCHEDULE=DYNAMIC Parallel execution with 4 threads Sum = -0.392987997483186611E+233 OMP_SCHEDULE=GUIDED Parallel execution with 4 threads Sum = 72378.0000000000000
Local fix
N/A
Problem summary
PROBLEM DESCRIPTION: When a forall statement that performs array self-assignment appears in a worksharing construct, the self-assigned array may get corrupted under the dynamic or guided OMP scheduling. USERS AFFECTED: Users of forall statements that perform array self-assignment inside a worksharing construct and run their application under the dynamic or guided OMP scheduling. The test case can be simplied further: program workshare use OMP_LIB implicit none integer, parameter :: n=10 integer :: i, j, num_th real(kind=4), dimension(n,n) :: a a(:,:)=1 !$OMP PARALLEL num_threads(4) private(i,j) !$OMP WORKSHARE forall (i=2:n, j=1:n-1, i>j) a(j,i) = a(i,j) !$OMP END WORKSHARE !$OMP END PARALLEL print *, sum(a) end program workshare
Problem conclusion
Made compiler temporary variable created for self-assignment inside forall non-private; the problem is fixed.
Temporary fix
Comments
APAR Information
APAR number
LI75464
Reported component name
XL FORTRAN SLES
Reported component ID
5724U8400
Reported release
C10
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt
Submitted date
2010-04-27
Closed date
2010-04-27
Last modified date
2010-04-27
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
Fix information
Fixed component name
XL FORTRAN SLES
Fixed component ID
5724U8400
Applicable component levels
RC10 PSY
UP
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Document Information
Modified date:
24 February 2022