Purpose
The DO SERIAL directive indicates to the compiler that the DO loop that is immediately following the directive must not be parallelized. This directive is useful in blocking automatic parallelization for a particular DO loop. The DO SERIAL directive only takes effect if you specify the -qsmp compiler option.
Format
>>-DO SERIAL--------------------------------------------------->< |
Rules
The first noncomment line (not including other directives) that is following the DO SERIAL directive must be a DO loop. The DO SERIAL directive applies only to the DO loop that immediately follows the directive and not to any loops that are nested within that loop.
You can only specify one DO SERIAL directive for a given DO loop. The DO SERIAL directive must not appear with the DO, or PARALLEL DO directive on the same DO loop.
White space is optional between DO and SERIAL.
You should not use the OpenMP trigger constant with this directive.
Examples
Example 1: An example with nested DO loops where the inner loop (the J loop) is not parallelized.
!$OMP PARALLEL DO PRIVATE(S,I), SHARED(A)
DO I=1, 500
S=0
!SMP$ DOSERIAL
DO J=1, 500
S=S+1
ENDDO
A(I)=S+I
ENDDO
Example 2: An example with the DOSERIAL directive applied in nested loops. In this case, if automatic parallelization is enabled the I or K loop may be parallelized.
DO I=1, 100
!SMP$ DOSERIAL
DO J=1, 100
DO K=1, 100
ARR(I,J,K)=I+J+K
ENDDO
ENDDO
ENDDO
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