Weak equivalence: example

C$OMP DO

DO 100 I=1,NDIM

TMP =ALG_KERNEL(I)

C$OMP CRITICAL

CALL COMBINE (TMP, RES)

C$OMP END CRITICAL

100 CONTINUE

C$OMP END PARALLEL

The summation into RES occurs one thread at a time, but in any order so the result is not bitwise compatible with the sequential program.

Much more efficient, but some users get upset when low order bits vary between program runs.

The summation into RES occurs one thread at a time, but in any order so the result is not bitwise compatible with the sequential program.