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OpenMP Home PageORDERED Directive
The code enclosed with ORDERED and END ORDERED directives is executed in the order in which iterations would be executed in a sequential execution of the loop. The ORDERED directive can only appear in the context of a DO or PARALLEL DO directive. It is illegal to branch into or out of an ORDERED block.
!$OMP ORDERED block !$OMP END ORDERED
Example
PROGRAM ORDERED
IMPLICIT NONE
INTEGER, PARAMETER:: N=1000, M=4000
REAL, DIMENSION(N,M):: X,Y
REAL, DIMENSION(N):: Z
INTEGER I,J
CALL RANDOM_NUMBER(X)
CALL RANDOM_NUMBER(Y)
Z=0.0
PRINT *, 'The first 20 values of Z are:'
!$OMP PARALLEL DEFAULT(SHARED) PRIVATE(I,J)
!$OMP DO SCHEDULE(DYNAMIC,2) ORDERED
DO I=1,N
DO J=1,M
Z(I) = Z(I) + X(I,J)*Y(J,I)
END DO
!$OMP ORDERED
IF(I<21) THEN
PRINT *, 'Z(',I,') =',Z(I)
END IF
!$OMP END ORDERED
END DO
!$OMP END DO
!$OMP END PARALLEL
END PROGRAM ORDERED
Compiling and running on franklin:
> cat ordered.pbs
#PBS -N ordered
#PBS -j oe
#PBS -o ordered.out
#PBS -q interactive
#PBS -S /bin/bash
#PBS -l mppwidth=1
#PBS -l mppnppn=1
#PBS -l mppdepth=2
#PBS -l walltime=00:05:00
#PBS -V
cd $PBS_O_WORKDIR
ftn -o ordered -mp=nonuma -Minfo=mp ordered.f90
export OMP_NUM_THREADS=2
aprun -n 1 -N 1 ./ordered
> qsub ordered.pbs
500980.nid00003
> cat ordered.out
/opt/xt-pe/2.0.44a2/bin/snos64/ftn: INFO: linux target is being used
ordered.f90:
ordered:
15, Parallel region activated
18, Parallel loop activated; dynamic iteration allocation
31, Barrier
Parallel region terminated
The first 20 values of Z are:
Z( 1 ) = 1028.067
Z( 2 ) = 1015.378
Z( 3 ) = 1010.786
Z( 4 ) = 1003.594
Z( 5 ) = 990.9749
Z( 6 ) = 982.2872
Z( 7 ) = 1021.567
Z( 8 ) = 1019.952
Z( 9 ) = 1011.410
Z( 10 ) = 986.6424
Z( 11 ) = 987.3596
Z( 12 ) = 992.1103
Z( 13 ) = 1001.674
Z( 14 ) = 1000.352
Z( 15 ) = 1021.354
Z( 16 ) = 1009.728
Z( 17 ) = 996.0969
Z( 18 ) = 1005.107
Z( 19 ) = 993.8898
Z( 20 ) = 981.4053
Application 4736903 resources: utime 22, stime 3
Without the ordered directive, sample output looks like this:
The first 20 values of Z are: Z( 3 ) = 1010.786 Z( 1 ) = 1028.067 Z( 2 ) = 1015.378 Z( 5 ) = 990.9749 Z( 6 ) = 982.2872 Z( 7 ) = 1021.567 Z( 8 ) = 1019.952 Z( 9 ) = 1011.410 Z( 10 ) = 986.6424 Z( 11 ) = 987.3596 Z( 12 ) = 992.1103 Z( 13 ) = 1001.674 Z( 14 ) = 1000.352 Z( 15 ) = 1021.354 Z( 16 ) = 1009.728 Z( 17 ) = 996.0969 Z( 18 ) = 1005.107 Z( 19 ) = 993.8898 Z( 20 ) = 981.4053 Z( 4 ) = 1003.594 Application 4736940 resources: utime 24, stime 2
