machines: eccc: set I_MPI_CBWR for BASEGEN/BASECOM runs

Intel MPI, in contrast to OpenMPI (as far as I was able to test, and see
[1], [2]), does not (by default) guarantee that repeated runs of the same
code on the same machine with the same number of MPI ranks yield the
same results when collective operations (e.g. 'MPI_ALLREDUCE') are used.

Since the VP solver uses MPI_ALLREDUCE in its algorithm, this leads to
repeated runs of the code giving different answers, and baseline
comparing runs with code built from the same commit failing.

When generating a baseline or comparing against an existing baseline,
set the environment variable 'I_MPI_CBWR' to 1 for ECCC machine files
using Intel MPI [3], so that (processor) topology-aware collective
algorithms are not used and results are reproducible.

Note that we do not need to set this variable on robert or underhill, on
which jobs have exclusive node access and thus job placement (on
processors) is guaranteed to be reproducible.

[1] https://stackoverflow.com/a/45916859/
[2] https://scicomp.stackexchange.com/a/2386/
[3] https://www.intel.com/content/www/us/en/develop/documentation/mpi-developer-reference-linux/top/environment-variable-reference/i-mpi-adjust-family-environment-variables.html#i-mpi-adjust-family-environment-variables_GUID-A5119508-5588-4CF5-9979-8D60831D1411

(cherry picked from commit 1f46305)
(this commit is available via

    git fetch https://github.com/CICE-Consortium/CICE refs/pull/774/head

and was squash-merged as part of 16b78da (ice_dyn_vp: allow for
bit-for-bit reproducibility under `bfbflag` (CICE-Consortium#774), 2022-10-20)).

configuration/scripts/machines/env.ppp5_intel

@@ -18,6 +18,10 @@ source $ssmuse -d /fs/ssm/main/opt/intelcomp/inteloneapi-2022.1.2/intelcomp+mpi+
 # module load -s icc mpi
 setenv FOR_DUMP_CORE_FILE 1
 setenv I_MPI_DEBUG_COREDUMP 1
+# Reproducible collectives
+if (${ICE_BASEGEN} != ${ICE_SPVAL} || ${ICE_BASECOM} != ${ICE_SPVAL}) then
+  setenv I_MPI_CBWR 1
+endif
 # Stop being buggy
 setenv I_MPI_FABRICS ofi
 # NetCDF

configuration/scripts/machines/env.ppp6_gnu-impi

@@ -18,6 +18,10 @@ setenv I_MPI_F90 gfortran
 setenv I_MPI_FC gfortran
 setenv I_MPI_CC gcc
 setenv I_MPI_CXX g++
+# Reproducible collectives
+if (${ICE_BASEGEN} != ${ICE_SPVAL} || ${ICE_BASECOM} != ${ICE_SPVAL}) then
+  setenv I_MPI_CBWR 1
+endif
 # Stop being buggy
 setenv I_MPI_FABRICS ofi
 

configuration/scripts/machines/env.ppp6_intel

@@ -18,6 +18,10 @@ source $ssmuse -d /fs/ssm/main/opt/intelcomp/inteloneapi-2022.1.2/intelcomp+mpi+
 # module load -s icc mpi
 setenv FOR_DUMP_CORE_FILE 1
 setenv I_MPI_DEBUG_COREDUMP 1
+# Reproducible collectives
+if (${ICE_BASEGEN} != ${ICE_SPVAL} || ${ICE_BASECOM} != ${ICE_SPVAL}) then
+  setenv I_MPI_CBWR 1
+endif
 # Stop being buggy
 setenv I_MPI_FABRICS ofi
 # NetCDF

configuration/scripts/machines/env.ppp6_intel19

@@ -17,6 +17,10 @@ setenv FOR_DUMP_CORE_FILE 1
 source $ssmuse -d /fs/ssm/hpco/exp/intelpsxe-impi-19.0.3.199
 setenv FI_PROVIDER verbs
 setenv I_MPI_DEBUG_COREDUMP 1
+# Reproducible collectives
+if (${ICE_BASEGEN} != ${ICE_SPVAL} || ${ICE_BASECOM} != ${ICE_SPVAL}) then
+  setenv I_MPI_CBWR 1
+endif
 # Stop being buggy
 setenv I_MPI_FABRICS ofi
 # NetCDF