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Sam Hatfield
Nemo
Commits
068e9098
Commit
068e9098
authored
3 years ago
by
Stefania Ciliberti
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add MPI3 option
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8b512a73
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doc/latex/NEMO/subfiles/chap_LBC.tex
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068e9098
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@@ -265,6 +265,13 @@ The data exchanges between processors are required at the very place where
lateral domain boundary conditions are set in the mono-domain computation:
the
\rou
{
lbc
\_
lnk
}
routine (found in
\mdl
{
lbclnk
}
module) which manages such conditions is interfaced with
routines found in
\mdl
{
lib
\_
mpp
}
module.
From the NEMO4.2 release, a new communication strategy has been introduced to preserve performance efficiency
by reducing communication time, namely the MPI3 neighborhood collective communications.
It provides a way to have sub-communicators used to perform collective communications only among neighborhood.
A single MPI message is needed to be built for all neighbours instead of 4 different messages before calling the collective.
The new communication approach can be selected by setting the value of
\np
{
nn
_
comm
}{
nn
\_
comm
}
parameter, defined in
\nam
{
mpp
}{
mpp
}
namelist.
\np
{
nn
_
comm
}{
nn
\_
comm
}
=1 activates the point to point communications.
Any value other than 1 (usually
\np
{
nn
_
comm
}{
nn
\_
comm
}
=2) can be used to select the collective communications.
The output file
\textit
{
communication
\_
report.txt
}
provides the list of which routines do how
many communications during 1 time step of the model.
\\
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