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MM5 Model on PC with Intel Compilers

November 24, 2004:

MM5 works well with versions 1.4 and 2.0 of the PathScale EKOPath(tm) Compiler Suite. We have tested versions 3.6.1 and 3.6.3 of MM5.

In order to build, we have had success with the following flags:

   FC = pathf90
   CC = pathcc
   FCFLAGS = -I$(LIBINCLUDE) -O3 -OPT:Ofast -fno-math-errno -DDEC_ALPHA
   CFLAGS = -O3 -OPT:Ofast -fno-math-errno -DDEC_ALPHA

To handle byte-swapped I/O correctly for MM5, use the following sequence of commands:

   FILENV=$HOME/.assign
   export FILENV
   assign -F f77.mips -N be g:su
   assign -I -F f77.mips -N be g:du

You only have to run the assign commands once, as they're stored in a file, but you must ensure that the FILENV environment variable is always set correctly before you run MM5.

We have verified that MM5 performs well on Opteron systems using these optimization options.

The MPP variant of MM5 (version 3.6.3) has been tested using LAM-MPI 7.1.1 and MPICH 1.2.6 in conjunction with the PathScale 1.4 and 2.0 compilers. This worked well and gave good performance on a small cluster of Opteron systems with Gigabit ethernet interconnect. A number of small bug fixes to the MM5-MPP source code are required. The most critical of these bug fixes is to the file MPP/mhz.c. It turns out that the PathScale compiler, at high optimization level, is able to completely optimize away the timing loops causing the mhz estimation level to hang. This optimization can be defeated with the following change:

164,165c164
< volatile int use_p_counter = 0;
< void use_p(int **p) { use_p_counter += (p != NULL); }
---
void use_p(int **p) {}

A patch of the necessary changes is available from support@pathscale.com

Thanks to Mark Debbage at Performance Engineer, PathScale Inc

To build MM5 with IFC version 8.0 for ia32 (Xeon), use these flags,

     FC = /opt/intel_fc_80/bin/ifort
     FCFLAGS = -I$(LIBINCLUDE) -pc 32 -rcd -fpp -convert big_endian

On ia64 (Itanium), use,

     FCFLAGS = -I$(LIBINCLUDE) -fpp -convert big_endian -DDEC_ALPHA

Be sure to use the latest version and patch level of the compiler, (l_fc_pc_8.0.039_pe043 as of this writing), as it contains some bug fixes that are relevant to MM5.

Comments on ICC :

• When using IFC 8.0 and "-convert big_endian", the "F_UFMTENDIAN" environment is not required.
• It is not necessary to make any changes to the source code (mp_stotndt.F or otherwise).
• The optimizations, -axiMKW -tpp6 may not be appropriate for all systems.
  • The -ax "i" flag is no longer supported in IFC 8.0,
  • The "-ax" argument is not available at all on Itanium systems.

To build MM5 for amd64 (Opteron), use the PGI compiler with -DDEC_ALPHA added to
FCFLAGS. When building with MPI, add it to the CFLAGS and CPPFLAGS definitions
as well.

Thanks to Marc Rieffel at Paracel
Users interested in determining the best optimization options for their specific target platforms are welcome to contact Paracel at info@paracel.com or to visit Paracel's Geosciences