On Wed, Jun 27, 2018 at 11:09:56AM +0300, Janne Blomqvist wrote:
>
> How about committing a patch changing to use TRUTH_{AND|OR}_EXPR, and then
> check benchmark results (polyhedron, spec etc.)? If performance worsens, we
> revert, if it improves, great, lets keep it?
>
> To clarify, I'm not objecting to using TRUTH_{AND|OR}_EXPR, I'm objecting
> to the notion that this is somehow "more correct" or "less bad" than the
> current short-circuiting. The Fortran standard does not specify an
> evaluation strategy; IMHO very unfortunately, but it is what it is.
>
Benchmarks aren't going to prove anything unless the
benchmarks have the specific construct under discuss.
Here's my benchmark that uses '.false. .and. check()'
construct. Note, check() has no side-effect.
% cat b.f90
program b
logical, external :: check
if (.false. .and. check()) then
print *, 'here'
else
print *, 'there'
end if
end program b
% cat a.f90
logical function check()
real x
10 call random_number(x)
if (x < 2) goto 10
check = .false.
end function check
% gfortran -o z a.f90 b.f90 && ./z
there
--
Steve
