-qstrict_induction
Category
@PROCESS
None.
Purpose
Prevents the compiler from performing induction (loop counter) variable optimizations. Such optimizations might be problematic when integer overflow operations involving the induction variables occurs.
Defaults
-qnostrict_induction
Usage
You should avoid specifying -qstrict_induction unless absolutely necessary, as it may cause performance degradation.
Examples
Consider the following two examples:
Example
1
integer(1) :: i, j ! Variable i can hold a
j = 0 ! maximum value of 127.
do i = 1, 200 ! Integer overflow occurs when 128th
j = j + 1 ! iteration of loop is attempted.
enddoExample 2
integer(1) :: i
i = 1_1 ! Variable i can hold a maximum
! value of 127.
100 continue
if (i == -127) goto 200 ! Go to label 200 once decimal overflow
i = i + 1_1 ! occurs and i == -127.
goto 100
200 continue
print *, i
endIf you compile these examples with the -qstrict_induction option, the compiler does not perform induction variable optimizations, but the performance of the code may be affected. If you compile the examples with the -qnostrict_induction option, the compiler may perform problematic optimizations.
Related information
