[Beowulf] g77 limits...
Florent.Calvayrac at univ-lemans.fr
Thu Feb 23 04:22:09 EST 2006
Robert G. Brown wrote:
> Dear List,
> What are the current limits on the size of arrays that can be allocated
> in g77? I know that this is almost a FAQ, but I cannot look back at the
> archives because it is so time dependent an answer. In particular, can
> an x64 box with a modern linux kernel and a modern g77 allocate 4-8 GB
> arrays (presuming, of course, that one uses a long int for an index)? I
> have seen references to "using an offset" in a few google hits (that
> were not very informative) -- does that basically mean doing pointer
> arithmetic in fortran?
it works without too much worrying about long ints
in g77 if you use the compile switch "-mcmodel=medium" ou -mcmodel=large.
(at least it is my experience on an Opteron64 box with Centos4.0 and
16Go of RAM)
> d) Where commercial compilers aren't a viable option (although I
> suggested them) -- the software has to build and be usable by e.g.
> researchers in countries where there simply is no money to spend on
isn't the Intel compiler available free of charge for students or demo
you give up support ?
Besides I found that for the ifc the
flag combination is helpful for large static arrays where heap
problems can appear
> The last suggests that it would be ideal if large arrays were at least
> approximately "transparent" -- so that the software would build on 32
> bit systems and be runnable there with smaller arrays but would also
> build and run on x64 big-memory systems without the need for extensive
> instrumentation of the code.
Works for me with g77.
Florent Calvayrac |
Directeur du SC Informatique Ressources Num. de l'Universite du Maine
Lab. de Physique de l'Etat Condense UMR-CNRS 6087
Inst. de Rech. en Ingenierie Molec. et Matx Fonctionnels FR CNRS 2575
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