PARAMETER Variable - helps optimization?

neverwillreply · ‎03-13-2006

Hi,

Does having compile-time constants that are labelled as "PARAMETER" help to compiler to optimize? For example, if there we have a

LOGICAL, PARAMETER :: testValue = .FALSE.

and then somewhere

IF (testValue) THEN
! Some code here
END IF

Can the compiler work out that no test is needed? In fact, does the compiler no even include the code "! Some code here".

Regards,

Nym.

Steven_L_Intel1 · ‎03-13-2006

In many cases, yes. PARAMETER constants and literal constants are treated the same here.

neverwillreply · ‎03-13-2006

Ok. So if there is some code

IF (.FALSE.) THEN
! Some code
END IF

Would the compiler include or not include the "! Some code" in the output file? Would the above three line be essentially removed?

Nym

TimP · ‎03-13-2006

You could check this, for your own case, by compiling with -S, to see whether code corresponding to those source lines was eliminated. Most likely, this would be done in dead code elimination phases of the compiler (not at -O0).