Re: Polyhedron b'marks | Linux vs Windows

[Evan Cooch <evan dot cooch at gmail dot com>]

> > So (the question) -- why? I have a couple of ideas, but I was wondering
> > if there is a short-form 'correct answer' (correct, as in, better than
> > my 'couple of ideas').
> >
> > Thanks in advance...
> Differences that large would make one suspect you didn't clean out 
> competing Windows processes, 

Meaning, I suspect, competing OS process, since the Polyhedron benchmark 
was the only user-initiated task. My next experiment will be to run the 
PB after booting Windows straight to the command line (i.e., absolute 
bare minimum of Windows functioning -- more or less 'straight to DOS', 
in the classical sense of a bygone era).

> or you have ridiculously small RAM, 

64 GB.  So, probably not this.  ;-)

> or something is wrong with your Windows gfortran.

Hmmm --- interesting.  I'm not sure what would be wrong with gfortran 
under Windows that wouldn't also be wrong under GNU/Linux, but, stranger 
things have happened.

> To a smaller extent, your excessive unrolling (as you didn't set e.g. 
> --param max-unroll-times=...) could hurt more on Windows. 

Easy enough to try -- thanks.

> Failing to set -march=native ought not to incur many differences if 
> both are set the same.  If  -march=native incurs failures, gfortran 
> 4.9 might be a fairer test (assuming it has corrected those failures).

I suppose worth a try.

What is interesting (and largely what motivated my original post) is 
that I have a number of colleagues who report more or less the same 
thing (and that it has been the case since at least gfortran 4.4).