A problem in the MPP version of MM5v3.3 has been observed on Linux
using Version 3.1-2 of the Portland Group pgf77 compiler. This was first
reported by Houjun Wang at Penn State. Symptoms are that the SOUND
routine outputs CFL violations and NaN values for TMASK (this will
appear in rsl.out.0000).

The suspected mechanism and workaround was developed by Al Bourgeois
(NCAR/MMM) in consultation with the Portland Group. It appears that
there is a subtle compiler bug, which can be gotten around by compiling
the code with -Kieee. Add this to the FCFLAGS in configure.user Section
7g.  This option causes assignment statements to result in writes to
memory, rather than using the FPU stack, which appears to be mishandled
by the compiler in the call to SFCRAD_COL within GSPBL.

Compiling and running with the diagnostic compiler option -Mchkfpstk
revealed the following fpu stack problem:

 ** WARNING: top of fp stack not empty on entry to sfcrad_col

There may be a slight degradation in performance from the -Kieee option.

It appears that only Linux-Pentium platforms using the Portland Group
compilers are affected.  It is unknown whether this affects the non-MPP
version of the model running on Linux.

---

Rotang, March 6, 2000