LFS and Fortran in Scyld Beowulf

Mikhail Kuzminsky kus at free.net
Tue Nov 9 01:00:01 PST 2010


According to Joe Griffin
> 
> g77 may be recompiled for large files.
> We use: -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE
> This allows:
> Formatted/Sequential   > 4 Gb
> Unformatted/Sequential < 4 Gb
> Unformatted/Direct     < 4 Gb
> Not quite limitless, but is gains from
> the 2 Gb limit.
  I think that like restrictions are very importatn for many
"beowulfers". By my opinion, large unformatted files are more
important than formatted, and 4 Gbytes restriction is inappropriate.
Of course, below I say about 32-bit CPUs( IA-32).

There is 2 different ways to supprot large files:
a) use special subset of system calls to open/read/write
   which allows to work with large files. This leads
  potentially to possible changes in the source.
  
  The pluses of this way is that they may be realized for more old
versions of kernel.

b) Use modern features of kernels 2.4.x and ext3fs 

   Unfortunately I'm not familiar w/restrictions in file sizes
at usual system calls in this environment. But theoreticaly
it's clear that I want to have large files w/usual open/read/write.
Sorry, if you say about restrictions in sizes (here and below) -
what do you mean - the ways w/changing of compiler source (and
run-time library sources) for more old kernels, or it's necessary
also for 2.4.x&ext3fs ?

> The CURRENT Intel compiler - 5.0.1 has a
> 2 Gb limit.  The next release to come out
> at the end of this month (6.0) will have
> the limit removed.
> 
  
Mikhail Kuzminsky
Zelinsky Institute of Organic Chemistry
Moscow



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