Subject: Advisory on using NCO on Cray T90
From: Charlie Zender (zender@cgd.ucar.edu)
Date: Tue May 04 1999 - 16:34:51 MDT
NCO is a suite of netCDF operators useful in analyzing CCM output
data. This advisory only concerns user's of NCO on Cray T90 machines.
NCO should be compiled with the -DC_ONLY flag on the Cray T90;
otherwise incorrect answers may result.
It appears that NCO assumes the wrong equivalence for the default
sizes of either floating point or integer types on the T90, and that
passing data between the Fortran and C halves of NCO is therefore
causing problems.
Without access to a T90, I cannot verify exactly what is happening,
but avoiding the C-Fortran interface problems by compiling with
-DC_ONLY appears to fix the problem.
Compiling with -DC_ONLY replaces all NCO Fortran code with C code.
The only downside to using -DC_ONLY is that averaging performance may
decrease somewhat since the C averaging code may need to perform more
pointer arithmetic than the Fortran code (depending on the compiler).
Due to problems such as this, 100% C code will probably be the default
in future versions of NCO.
Charlie
-- Charlie Zender Voice: (303) 497-1445, FAX: 497-1400 NCAR ACD & CGD E-mail: zender@ncar.ucar.edu P.O. Box 3000 URL: http://www.cgd.ucar.edu/cms/zender Boulder CO 80307-3000 PGP: finger -l zender@goldhill.cgd.ucar.edu
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