infra, FMS_cap: stdout_if_root() #1392
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This needs to be reviewed by @nikizadehgfdl before being merged. ✔️ Niki has confirmed to me that this is working. |
This patch adds `stdout_if_root` to the MOM_io API, and points to the FMS `stdout()` function in the FMS infra implementations. This change was required because calls to `coupler_type_write_chksums` handles both its own checksums across ranks and its own IO to `outunit`. Typically only the root PE will write the result. The FMS `stdout()` function would return the designated stdout unit for the root PE, and the internal `etc_unit` for other PEs, usually set to `/dev/null`. When MOM_io switched from using the FMS `stdout()` function to the `stdout` unit as defined in `iso_fortran_env`, this functionality was lost and every PE would write the same result to stdout. Normally this was controlled with `if (root)`-like tests, but this cannot be used in functions like `coupler_type_write_checksums`, which require participation of all PEs. We decided the only resolution here was to introduce a new function, `stdout_if_root` which replicates the original behavior of `stdout()`. Additional comments: * The `if (root)` checks were retained, since it is presumably still a good idea to avoid the `write()` calls when possible, even to `/dev/null`. * This patch only updates the FMS coulper driver, but I would recommend that the other driver maintainers review their own calls to this function.
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PR was updated to rename |
marshallward
changed the title
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This PR has passed pipeline testing at https://gitlab.gfdl.noaa.gov/ogrp/MOM6/-/pipelines/12667. |
Hallberg-NOAA
approved these changes
May 15, 2021
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This patch adds
get_root_stdoutto the MOM_io API, and points to theFMS
stdout()function in the FMS infra implementations.This change was required because calls to
coupler_type_write_chksumshandles both its own checksums across ranks and its own IO to
outunit.Typically only the root PE will write the result.
The FMS
stdout()function would return the designated stdout unit forthe root PE, and the internal
etc_unitfor other PEs, usually set to/dev/null.When MOM_io switched from using the FMS
stdout()function to thestdoutunit as defined iniso_fortran_env, this functionality waslost and every PE would write the same result to stdout.
Normally this was controlled with
if (root)-like tests, but thiscannot be used in functions like
coupler_type_write_checksums, whichrequire participation of all PEs.
We decided the only resolution here was to introduce a new function,
get_root_stdoutwhich replicates the original behavior ofstdout().Additional comments:
The
if (root)checks were retained, since it is presumably still agood idea to avoid the
write()calls when possible, even to/dev/null.This patch only updates the FMS coulper driver, but I would recommend
that the other driver maintainers review their own calls to this
function.