Possible Code Performance Disparity using "parameter"

[Steve Kargl]

On Mon, Mar 12, 2012 at 06:03:11PM -0400, John L. Males wrote:
> 
> Any thoughts or comments with regards to this discovery?
> 

Without seeing the code, one can say very little.

You do realize that the PARAMETER attribute in a type
declaration statement makes an entity a named constant
and not a variable.  When it is a named constant, gfortran
will replace the entity by the actual value, which may
permit constant-folding and other optimizations (such
as hositing a (sub)expression out of a loop).  Depending
on how complicated the code is and how you use the 
entity when it is a variable, the generated code may
actually be read its value from memory on each iteration.
 
-- 
Steve