[Ncep.list.nems.announce] Comments Requested: Moving FMS out of MOM6 and FV3 repos

Cecelia DeLuca - NOAA Affiliate cecelia.deluca at noaa.gov
Tue Aug 28 15:58:20 UTC 2018

Hi Sam, if this is true:  This means the FV3 GFS will not be usable except
with certain versions of the Intel compiler.
I think the policies here require management attention before taking next


On Mon, Aug 27, 2018 at 7:47 PM, Samuel Trahan - NOAA Affiliate <
samuel.trahan at noaa.gov> wrote:

> Hi all,
> We have a proposed commit that is urgently needed, but may have major
> negative impacts to a lot of users.  Please read this email and comment.
> Our comment period ends at noon Tuesday, September 4.  The commit, if
> accepted, will happen Wednesday, September 5.
> *The Commit: Overview*
> In NEMS apps, the FMS exists within both the FV3 and MOM6 repositories;
> hence some apps have two copies of FMS.  We have a proposed commit that
> will move the FMS up one level so there is only one FMS per app.  The FMS
> we've chosen is the one from the GFDL repository.  The technical details of
> the changes, are largely inconsequential; the main issue is the choice of
> repositories.
> *Consequences*
> These are the consequences of choosing GFDL's FMS repository.
> 1. Portability changes to the FMS will be lost permanently because GFDL
> rejected them.  This means the FV3 GFS will not be usable except with
> certain versions of the Intel compiler.  This has been confirmed.
> 2. Recent and upcoming FMS bug fixes will be lost because they are not in
> the GFDL repository.
> 3. In general, any FV3 changes will have to wait several weeks if they
> need changes to FMS.
> Items #2 and #3 are unavoidable.  GFDL FMS has a large userbase and
> lengthy test process.  They will, out of necessity, have a long delay
> before commits.
> *Alternatives*
> I know of three alternatives to our FMS repository problem.  Any of these
> may require funding or tasking changes, in or from NOAA:
> 1. GFDL handles the FV3 GFS as a special case, maintaining a branch of FMS
> for the FV3 GFS, and applying changes within 2-3 days.  GFDL ports FMS to
> other compilers.
> 2. DTC maintains a fork of FMS which all NEMS apps use.  DTC maintains any
> portability changes and regularly pulls changes from GFDL FMS.  They
> receive any changes needed for NEMS coupling and resolve conflicts as
> needed.
> 3. EMC maintains the aforementioned fork.
> Note that DTC is presently tasked with porting the FMS, and has
> successfully ported it to other platforms and maintained an FMS repository.
> *The Branches*
> The changes can be found in the "fms-component" branches of the NEMSfv3gfs
> and EMC_FV3-MOM6-CICE5 repositories.  These will be updated later this week
> when incoming FV3 changes are available.  We will be sure to test before
> committing to the relevant branches.
> When testing this yourself, note that the EMC_FV3-MOM6-CICE5 warm start
> test will not reliably reproduce itself; this is a known issue that is
> unrelated to this commit.  Jet baselines are out-of-date, so you cannot
> test there.  All other tests should pass for both apps on all supported
> platforms.
> *The Commit: Details*
> Overview of the changes:
> 1. FMS is removed from the build system in MOM6 and FV3
> 2. FMS is added at the app level from git://github.com/NOAA-GFDL/FMS.
> The "git" url makes this submodule read-only.  That is a workaround for
> problems in the installation of "git" on WCOSS Cray and Dell which make
> github unreachable via https.  This "git" installation problem has been a
> known issue for several months and remains unresolved, so such a workaround
> is necessary.
> 3. The FMS/fv3gfs directory is updated to be able to build FMS outside of
> FV3.  This change was accepted by GFDL in their repository.
> 4. The NEMSAppBuilder is updated to build FMS.  It is treated the same way
> as a coupled component in the build system.
> 5. Any appBuilder files must include FMS before FV3 or MOM6 in their
> component list.
> 6. The NEMSfv3gfs tests/compile.sh is updated to build FMS before FV3.
> Sincerely,
> Sam Trahan
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