6.2.5 C*$* assert permutation

The C*$* assert permutation assertion provides KAP with sufficient information to allow KAP to generate optimized code for certain types of indirect addressing (INTEGER arrays used in subscripts). This assertion requires /optimize=4 or higher. The following example shows when it is unsafe to optimize a DO loop:

DO 100 I = 1,N
          A(IP (I)) = A(IP (I)) + B(I)
100  CONTINUE

KAP cannot safely generate optimized code because it cannot tell if the different values in the index array IP overlap. If all values in I are distinct, the optimized code is correct; if some of the values are the same, the optimized code may be unsafe. You can tell KAP that the values in the index array IP are all distinct with the following assertion:

C*$*ASSERT PERMUTATION( IP )
         DO 100 I=1,N
            A(IP (I)) = A(IP (I)) + B(I)
100  CONTINUE

With the addition of this assertion, KAP knows that it can safely generate optimized code for this loop. If at run time the values of IP are not distinct, the optimized code may generate incorrect results.