LFS and Fortran

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


> On Tue, 26 Mar 102, Mikhail Kuzminsky wrote:
> > According to Joe Griffin
> > > g77 may be recompiled for large files.
> > > We use: -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE
> ..
> > > Unformatted/Sequential < 4 Gb
> >   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.
> 
> LFS support is much more important for Beowulf systems than the average
> workstation user.
> 
> > a) use special subset of system calls to open/read/write
> ..
> > b) Use modern features of kernels 2.4.x and ext3fs
> 
> The LFS kernel support has some limitations, many of which remain true
> for 2.4 kernels.  First, the offset is really only 40/41/42 bits, not 64
> bits, because we still use 32 bit block offsets with 512/1K blocks.
> Very few places have a single file larger than 4TB, so this isn't a
> current problem.
> 
  In many cases 40-42 bits is enough (at least it gives more disc space
than it exist on the node - if I use some modern HDDs per node).

  My questions concern more to Linux itself than to Scyld distribution.
There is 3 possible "levels" of large files support for application
programs written on F77

a) I use statically linked binaries created under more old Linux versions. 
 I suppose that this binaries use standard run-time libraries w/o 
special 64-bit open/read/write calls.
 
Is it possible to work w/large files if I'll run this binaries on
2.4.x w/ext3 or ext2 ?

b) I use the same binaries but w/dynamic linking, and may change 
g77/pgf77/ifc run-time library to more new version. 

Is it enough for work w/large files under 2.4.x w/ext3 or ext2 ?

c) It's possible to re-translate f77 source with some modern
version of compiler to receive large files support.

It's clear now that g77 3.1 (or specially precompiled but more old g77 version)
and ifc 6.0 will be enough ; but was is about pgf77 versions ?
 

Yours
Mikhail Kuzminsky
Zelisnky Institute of Organic Chemistry
Moscow



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