[Beowulf] Fortran Array size question

Nifty Tom Mitchell niftyompi at niftyegg.com
Wed Nov 4 19:36:20 EST 2009


On Tue, Nov 03, 2009 at 08:27:22PM -0500, "C. Bergström" wrote:
> Michael H. Frese wrote:
> >I think Gus has it right.  Your two arrays are 200 million
> >floating point words each, perhaps 8 bytes per word, and therefore
> >are approximately about 3  gigabytes total.
> >
> >That's too big for the default 'small' memory model.
> >
> >Certainly, there are no limits to array sizes in Fortran.
> If you need a 64bit Fortran compiler ping me off list. (PathScale
> not iFort of course)  I was working with some extremely large code a
> few months ago and one of our engineers could probably polish up my
> patch and send out test binaries to anyone interested.  All we would
> ask for in this specific case is feedback.
> 
> <marketing>Our performance on floating point code should be better
> than Intel's.  If you find to the contrary that's a bug we're happy
> to address</marketing>

If I recall the pathscale compiler also needs a flag to establish
the memory model at compile time.   

One thing I cannot answer off the top of my head is if there is a need
to also establish the memory model for libraries. Since all libs are not
the same some will and some will not.  If there is any doubt when debugging 
check that the compile flags are consistant.




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