In general, when KAP inserts an iteration-local temporary, the
last value assigned to that temporary must be reassigned to the
original scalar. When /optimize is set to 2 or higher,
KAP performs lifetime analysis to determine if the value of the
original scalar is used outside the loop. When the command qualifier
/save=a is in effect (the default), live variable
analysis will be performed to identify scalar local variables in
subroutines and functions that require that their values be retained
invocations.
KAP determines if it is possible to reuse the result computed in the loop later in the program unit. If so, the variable is assigned the value it would have received in the serial loop, as shown in the following example:
DO 20 I=1,N DO 20 J=1,N X = A(I,J) Y = B(I,J) 20 C(I,J) = X + Y PRINT *, X
Becomes:
LL1 = N .GT. 0 DO 3 I=1,N DO 2 J=1,N C(I,J) = A(I,J) + B(I,J) 2 CONTINUE IF (LL1) X = A(I,N) 3 CONTINUE PRINT *, X
The roundoff=0 qualifier was used to disable memory
management.