Sequential Equivalence isn’t a Silver Bullet

In this example, RAND() may not be thread safe. Even if it is, the pseudo-random sequences might overlap thereby throwing off the basic statistics.

C$OMP& PRIVATE(I, ID, TMP, RVAL)

ID = OMP_GET_THREAD_NUM()

N = OMP_GET_NUM_THREADS()

RVAL = RAND ( ID )

C$OMP DO

DO 100 I=1,NDIM

RVAL = RAND (RVAL)

TMP =RAND_ALG_KERNEL(RVAL)

C$OMP CRITICAL

CALL COMBINE (TMP, RES)

C$OMP END CRITICAL

100 CONTINUE

C$OMP END PARALLEL

This program follows the weak PSE rules, but its still wrong.