To run the OASIS3 executable on more than one process in IPSL parallelisation mode, OASIS3 must be compiled with the CPP key use_oasis_para (see 8.1.2).
With IPSL parallelisation mode, each OASIS3 process is totally independent of the others. Therefore, the user has to provide one separate configuration file per process and the different files must be named namcouple_x where x is the number of the corresponding OASIS3 process. Each OASIS3 process will receive, treat, and send the coupling fields described in its configuration file namcouple_x. Note that if OASIS3 was compiled with the CPP key use_oasis_para, the configuration file suffix is mandatory, even if OASIS3 runs in fact with only one process - in this case, the suffix is _0.
Although this parallelisation mode presents the advantage of removing the bottleneck that can appear when only one OASIS process receives and sends all the coupling fields, there are few constraints associated:
If the maximum number of prism_def_var_proto called by ANY component model in the coupled system is greater than twice the number of fields listed in the namcouple_x (which is often the case when OASIS3 is used in parallel mode), this maximum number of prism_def_var_proto has to be specified on the same line (below the $NFIELDS keyword) after the total number of fields exchanged (see also section 5.2).