This task is a continuation of the 2020 tiling work (#2365).

Workplan action

Wikipage: wiki:2021WP/HPC-02_Daley_Tiling

Context

additional loops were added for vectorial optimization in ldfslp.F90/ldf_slp.

Their "do ji=... / do jj=.." have not been replaced by DO loops rewriting :

https://forge.ipsl.jussieu.fr/nemo/browser/NEMO/trunk/src/OCE/LDF/ldfslp.F90 lines 247 and 323

Analysis

They are useless now. They can be removed. It won't change the results.

Fix

...

Context

1) Review, simplification and cleaning of the MPI interface is needed 2) There is a few bugs:

• potential bug with the corners if nn_hls > 1 (or 2?) with point-to-point communication
• collective communications is not working with BDY (as BDY has its own exchanges)

3) There is other things to further improve:

• do not send/receive if send/receive only land points (depend on nn_hls)
• send/receive only the oce values (checking mask, depend on nn_hls)
• keep in memory the send/receive buffers (if they are not too big for ex < jpi*jpj) from one call to another -> for point-to-point put the mpi_waitall at the beginning of next call
• make sure the north pole folding does not need east-west comm. done if nogather = F. to be done if nogather = T... so we could place it where we want (no need to wait for east-west comm).
• if north pole folding: force the last row of MPI-subdomains to have jpj much smaller (the smallest value?) so they go faster and other don't wait for them

Workplan action

Wikipage: wiki:2021WP/HPC-01_SebEtCie_MPI_Interface