Liking the MPAS code Much More than Model II or ModelE

I’ve only been into it about 10 minutes, but already I’m liking the MPAS code a LOT more than the stuff from Hansen and that “Hansen Labs” (aka NASA / NOAA / NCDC / etc.)

I was first pointed at this by rogercaiazza in a comment here:

https://chiefio.wordpress.com/2017/11/28/circles-and-hexagons-and-models-oh-my/#comment-88879

So h/t to Roger!

Some specifics:

Building Environment

The “Makefile” lists several compiler and systems choices, largely large… so “some assembly required” to make it go on tiny iron. It does have a gfortran option called out, and an mpif90 option; so mostly finding out what FORTRAN compilers are available and who lines up with whom.

Here’s a couple of sample blocks from the topmost Makefile (that sets the environment for all the rest):

titan-cray:
        ( $(MAKE) all \
        "FC_PARALLEL = ftn" \
        "CC_PARALLEL = cc" \
        "FC_SERIAL = ftn" \
        "CC_SERIAL = gcc" \
        "FFLAGS_PROMOTION = -default64" \
        "FFLAGS_OPT = -s integer32 -O3 -f free -N 255 -em -ef" \
        "CFLAGS_OPT = -O3" \
        "LDFLAGS_OPT = -O3" \
        "FFLAGS_OMP = " \
        "CFLAGS_OMP = " \
        "CORE = $(CORE)" \
        "DEBUG = $(DEBUG)" \
        "USE_PAPI = $(USE_PAPI)" \
        "OPENMP = $(OPENMP)" \
        "CPPFLAGS = $(MODEL_FORMULATION) -D_MPI -DUNDERSCORE" )

[... skipping some -EMS ]

gfortran:
        ( $(MAKE) all \
        "FC_PARALLEL = mpif90" \
        "CC_PARALLEL = mpicc" \ 
        "CXX_PARALLEL = mpicxx" \
        "FC_SERIAL = gfortran" \
        "CC_SERIAL = gcc" \
        "CXX_SERIAL = g++" \
        "FFLAGS_PROMOTION = -fdefault-real-8 -fdefault-double-8" \
        "FFLAGS_OPT = -O3 -m64 -ffree-line-length-none -fconvert=big-endian -ffree-form" \
        "CFLAGS_OPT = -O3 -m64" \ 
        "CXXFLAGS_OPT = -O3 -m64" \
        "LDFLAGS_OPT = -O3 -m64" \
        "FFLAGS_DEBUG = -g -m64 -ffree-line-length-none -fconvert=big-endian -ffree-form -fbounds-check -fbacktrace -ffpe-trap=invalid,zero,overflow" \
        "CFLAGS_DEBUG = -g -m64" \
        "CXXFLAGS_DEBUG = -O3 -m64" \
        "LDFLAGS_DEBUG = -g -m64" \
        "FFLAGS_OMP = -fopenmp" \
        "CFLAGS_OMP = -fopenmp" \
        "CORE = $(CORE)" \ 
        "DEBUG = $(DEBUG)" \
        "USE_PAPI = $(USE_PAPI)" \
        "OPENMP = $(OPENMP)" \
        "CPPFLAGS = $(MODEL_FORMULATION) -D_MPI -DUNDERSCORE" )

gfortran-clang:
        ( $(MAKE) all \
        "FC_PARALLEL = mpif90" \
        "CC_PARALLEL = mpicc -cc=clang" \
        "CXX_PARALLEL = mpicxx -cxx=clang++" \
        "FC_SERIAL = gfortran" \
        "CC_SERIAL = clang" \
        "CXX_SERIAL = clang++" \
        "FFLAGS_PROMOTION = -fdefault-real-8 -fdefault-double-8" \
        "FFLAGS_OPT = -O3 -m64 -ffree-line-length-none -fconvert=big-endian -ffree-form" \
        "CFLAGS_OPT = -O3 -m64" \
        "CXXFLAGS_OPT = -O3 -m64" \
        "LDFLAGS_OPT = -O3 -m64" \
        "FFLAGS_DEBUG = -g -m64 -ffree-line-length-none -fconvert=big-endian -ffree-form -fbounds-check -fbacktrace -ffpe-trap=invalid,zero,overflow" \
        "CFLAGS_DEBUG = -g -m64" \
        "CXXFLAGS_DEBUG = -O3 -m64" \
        "LDFLAGS_DEBUG = -g -m64" \
        "FFLAGS_OMP = -fopenmp" \
        "CFLAGS_OMP = -fopenmp" \
        "CORE = $(CORE)" \
        "DEBUG = $(DEBUG)" \
        "USE_PAPI = $(USE_PAPI)" \
        "OPENMP = $(OPENMP)" \
        "CPPFLAGS = $(MODEL_FORMULATION) -D_MPI -DUNDERSCORE" )

The g95 spec also includes mpif90 as the parallel fortran compiler, and I didn’t find one with a simple “apt-get” so more poking around needed (could be just some odd name with release level appended or ‘whatever’…)

The code itself ends with .F and Linux seems to think they are just ascii files, so one assumes the nature of modern fortran has moved far enough from the original for the “file” command to not recognize it (or it needs .f ending).

Also, all the endian settings list “big”, so what to do on a little-endian machine?… One hopes the compiler is flexible enough to deal with that.

The Code

The code, from a very small sample, looks very well written and well commented. As a “community project”, I’d expect that since “many hands” means many eyes needing to find clue…

From:

chiefio@odroidxu4:~/MPAS/MPAS-Release-5.2/src/core_atmosphere$ h

 vi physics/mpas_atmphys_functions.F 

An example:

! Copyright (c) 2013,  Los Alamos National Security, LLC (LANS)
! and the University Corporation for Atmospheric Research (UCAR).
!
! Unless noted otherwise source code is licensed under the BSD license.
! Additional copyright and license information can be found in the LICENSE file
! distributed with this code, or at http://mpas-dev.github.com/license.html
!
!=================================================================================================================
 module mpas_atmphys_functions

 implicit none
 private
 public:: gammln,gammp,wgamma,rslf,rsif


 contains


!=================================================================================================================
!NOTE: functions rslf and rsif are taken from module_mp_thompson temporarily for computing
!      the diagnostic relative humidity. These two functions will be removed from this module
!      when the Thompson cloud microphysics scheme will be restored to MPAS-Dev.
!      Laura D. Fowler (birch.mmm.ucar.edu) / 2013-07-11.

!+---+-----------------------------------------------------------------+
      SUBROUTINE GCF(GAMMCF,A,X,GLN)
!     --- RETURNS THE INCOMPLETE GAMMA FUNCTION Q(A,X) EVALUATED BY ITS
!     --- CONTINUED FRACTION REPRESENTATION AS GAMMCF.  ALSO RETURNS
!     --- LN(GAMMA(A)) AS GLN.  THE CONTINUED FRACTION IS EVALUATED BY
!     --- A MODIFIED LENTZ METHOD.
!     --- USES GAMMLN
      IMPLICIT NONE
      INTEGER, PARAMETER:: ITMAX=100
      REAL, PARAMETER:: gEPS=3.E-7
      REAL, PARAMETER:: FPMIN=1.E-30
      REAL, INTENT(IN):: A, X
[...]
!  (C) Copr. 1986-92 Numerical Recipes Software 2.02
!+---+-----------------------------------------------------------------+
      SUBROUTINE GSER(GAMSER,A,X,GLN)
!     --- RETURNS THE INCOMPLETE GAMMA FUNCTION P(A,X) EVALUATED BY ITS
!     --- ITS SERIES REPRESENTATION AS GAMSER.  ALSO RETURNS LN(GAMMA(A))
!     --- AS GLN.
!     --- USES GAMMLN
      IMPLICIT NONE
      INTEGER, PARAMETER:: ITMAX=100
      REAL, PARAMETER:: gEPS=3.E-7
      REAL, INTENT(IN):: A, X
      REAL:: GAMSER,GLN
      INTEGER:: N
      REAL:: AP,DEL,SUM
      GLN=GAMMLN(A)
      IF(X.LE.0.)THEN
        IF(X.LT.0.) PRINT *, 'X < 0 IN GSER'
        GAMSER=0.
        RETURN
      ENDIF
      AP=A
      SUM=1./A
      DEL=SUM
      DO 11 N=1,ITMAX
        AP=AP+1.
        DEL=DEL*X/AP
        SUM=SUM+DEL
        IF(ABS(DEL).LT.ABS(SUM)*gEPS)GOTO 1
 11   CONTINUE
      PRINT *,'A TOO LARGE, ITMAX TOO SMALL IN GSER'
 1    GAMSER=SUM*EXP(-X+A*LOG(X)-GLN)
      END SUBROUTINE GSER
!  (C) Copr. 1986-92 Numerical Recipes Software 2.02

I jumped down to where they included a proprietary subroutine, yet it is under BSD license. Go figure.

Yet the style is easy to follow and the general purpose set out in comments. Nice.

So I’m going to wander through more of this code before I say much more about it. This is just the first blush and who knows what’s under the covers. What I can say with certainty is that open projects with many hands and eyes benefit greatly from the corrective efforts of the group. Nobody wants to explain their stupid human trick more than once to a Noob who spotted it ;-)

How to get it

They have a place where you can download a zip file for those of you not on *nix systems. Then there’s a place to fill in a sign-up for what you are doing with it. Nicely, you can skip the sign up (since I’m just a looky lou it’s a waste of everyone’s time at this point) and do a direct tarball download (for us *nix folks).

The direct download (both zip and tarball)

https://github.com/MPAS-Dev/MPAS-Release/releases

Directions and helpful info they want you to read, fully, before the download. (I’ll get to it IF I ever start to build / compile the thing ;-) Mostly it looks like help to push folks into using git, which is fine for folks who know git, or do systems work regularly; but not so fine if you just want to unpack a tarball and look it over…

https://mpas-dev.github.io/model.html

The request for a “registration”:

https://mpas-dev.github.io/registration.html

The top level of the download tree, which includes links that have names like “sample imput files”, oh the joy!…

http://mpas-dev.github.io/atmosphere/atmosphere_download.html

In Conclusion

I don’t know that this is the place I’ll be happy, but it sure is less musty and opaque than the alternatives to date. There’s also just a feeling like folks who think of scaling hexagonal grids have clue and like a tidy mind…

Time will show if first impression stand up, but so far I’m impressed.

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