= ''Name and subject of the action''

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== Summary

Analysis of scalability improvement using MPI3 new communications (e.g. collective neighbours communications) instead of point to point communications.

ticket: #2011
== Preview 

{{{
Mirek Andrejczuk

Plan outlined in ticket #2011 is OK. Most likely changes to the code will be limited to LBC/lib_mpp.F90. 
I'm happy to test the changes in MO operational configurations. May be worth considering implementation 
in which changing the number of halo points is easy.
}}}

== Tests

{{{#!box help
[[Include(wiki:Developers/DevProcess#tests)]]
}}}

{{{
The change improves the communication time. Preliminary tests show an improvement within a range of 18%-32% on the GYRE_PISCES configuration (with nn_GYRE=200), depending on the allocated number of cores

Results of the required bit comparability tests: No differences between outputs

This change preserves all diagnostics
}}}

== Review

{{{#!box help
[[Include(wiki:Developers/DevProcess#review)]]
}}}