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

Wed Sep 5 17:36:25 UTC 2018

Hi all,

We are still awaiting a management decision on how the FMS will be handled
in NEMS applications.  The "FMS component" commit will go in, in its
current form, but I don't know yet where the FMS will reside.

Sincerely,
Sam Trahan

On Wed, Aug 29, 2018 at 1:00 PM, Samuel Trahan - NOAA Affiliate <
samuel.trahan at noaa.gov> wrote:

> Hi all,
>
> We're close to having a solution to the aforementioned problem.  The
> details are uncertain at this time, but we'll have some kind of joint
> EMC-DTC fork of FMS in github.  It will track the GFDL FMS as closely as
> possible, while making it portable enough to use on all RDHPCS machines and
> common clusters elsewhere.  The NEMS applications will point to the EMC-DTC
> fork.  Management is ruminating on details like exactly where it will be,
> the choice of code manager, the commit process, and how the changes are
> sent back to GFDL; we expect to have a solution soon.  These may sound like
> mundane details, but having a poor code management process causes major
> problems if it goes on for too long.
>
> The commit will go in soon, but it may be slightly later than intended.
> We'll still try to get it in by Wednesday afternoon, but it may be later in
> the week if decisions on code management practices take a lot more
> discussion time.  We do expect the commit to be in by the end of next week
> though.
>
> I'll send out another update when I have more information.
>
> Sincerely,
> Sam Trahan
>
> On Mon, Aug 27, 2018 at 9:47 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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