1 General architecture

• OASIS3-MCT is (only) a coupling library

  Much of the underlying implementation of OASIS3 was refactored to leverage the Model Coupling Toolkit (MCT). OASIS3-MCT is a coupling library to be linked to the component models and that carries out the coupling field transformations (e.g. remappings/interpolations) in parallel on either the source or target processes and that performs all communication in parallel directly between the component models; there is no central coupler executable anymore¹⁵.

• MAPPING transformation to use a pre-defined mapping file

  With MAPPING, OASIS3-MCT has the ability to read a predefined set of weights and addresses (mapping file) specified in the namcouple to perform the interpolation/remapping. The user also has the flexibility to choose the location and the parallelization strategy of the remapping with specific MAPPING options (see section 4.3).

• Mono-process mapping file generation with the SCRIP library

  But as before, OASIS3-MCT_1.0 can also generate the mapping file using the SCRIP library (Jones 1999). When this is the case, the mapping file generation is done on one process of the model components; all previous SCRIPR remapping schemes available in OASIS3.3 are still supported besides BICUBIC and CONSERV/SECOND. (Note: these remapping schemes, not available in OASIS3-MCT_1.0 were reactivated in OASIS3-MCT_2.0, see B.4.)

• MPI2 job launching is NOT supported.

  Only MPI1 start mode is allowed. As before with the MPI1 mode, all component models must be started by the user in the job script in a pseudo-MPMD mode; in this case, they will automatically share the same MPI_COMM_WORLD communicator and an internal communicator created by OASIS3-MCT needs to be used for internal parallelization (see section 2.2.2).

Footnotes

... anymore¹⁵

As with OASIS3.3, the “put” calls are non-blocking but the “get” calls are blocking. As before, the user has to take care of implementing a coupling algorithm that will result in matching “put” and “get” calls to avoid deadlocks (see section 2.2.7). The lag (LAG) index works as before in OASIS3.3 (see section 2.5.3)