The main
objectives of the Code Coupling and IO PAE (PRISM Area of Expertise)
are to continue the development of the OASIS4 coupler and
give support to the groups that started using this coupler, and
maintain and support the OASIS3 coupler.
The OASIS3 and OASIS4 couplers, developed in the framework of the EU
FP5 PRISM project, are software allowing synchronized exchanges of
coupling information between numerical codes representing different
components of the climate system.
OASIS3 is the direct evolution of the OASIS coupler developed since
more than 10 years at CERFACS (Toulouse, France). Portability and
flexibility are OASIS3 key design concepts. At run-time, OASIS3 acts as
a separate mono process executable, which main function is to
interpolate the coupling fields exchanged between the component models,
and as a library linked to the component models, the OASIS3
PRISM Model Interface Library (OASIS3 PSMILe). OASIS3 supports 2D
coupling fields only. To communicate with OASIS3, directly with another
model, or to perform I/O actions, a component model needs to include
few specific PSMILe calls. OASIS3 PSMILe supports in particular
parallel communication between a parallel component model and OASIS3
main process based on Message Passing Interface (MPI) and file I/O
using the GFDL mpp_io library. OASIS3 has been extensively used
in the PRISM demonstration runs and is currently used by approximately
10 climate modelling groups in Europe, USA, Canada, Australia, India
and Brasil.
As the climate modelling community is progressively targeting higher
resolution climate simulations run on massively parallel platforms with
coupling exchanges involving a higher number of (possibly 3D) coupling
fields at a higher coupling frequency, a new fully parallel coupler
OASIS4 has also been developed within PRISM. The concepts of
parallelism and efficiency drove OASIS4 developments, at the same time
keeping in its design the concepts of portability and flexibility that
made the success of OASIS3. During the run, OASIS4 Driver extracts the
configuration information defined by the user in XML files and
organizes the process management of the coupled simulation. OASIS4
Transformer performs, in a fully parallel mode, the interpolation of
the coupling fields. OASIS4 supports 3D and 2D coupling fields. To
interact with the rest of the coupled model, the component models have
to include specific calls to the OASIS4 PRISM System Model Interface
Library (OASIS4 PSMILe), which, at runtime performs fully parallel the
MPI-based exchanges of coupling data including automatic
repartitioning, either directly or via additional Transformer
processes, and file I/O using the GFDL mpp_io library. OASIS4
portability and scalability have been demonstrated with different "toy"
models and OASIS4 has also been used to realize the coupling between
the MOM4 ocean model and a pseudo atmosphere model.
The OASIS4 PSMILe Application Programming Interface (API) was kept as
close as possible to OASIS3 PSMILe API. This should ensure a smooth
and progressive transition between OASIS3 and OASIS4 use in the climate
modelling community.
See also
OASIS
page at CERFACS.