MOAB support in ESMF 8.1.0

[Plantain]

ESMF has added support for MOAB as a new internal mesh representation. Does that have potential to improve performance in xESMF?

https://github.com/esmf-org/esmf/releases/tag/ESMF_8_1_0
""ESMF is in the process of upgrading the internal mesh representation to use the MOAB mesh library developed by the U.S. Department of Energy. In this release, ESMF capabilities using MOAB have been significantly optimized and expanded, allowing for application-level testing of ESMF with MOAB as the underlying mesh representation. MOAB is built into the ESMF library by default, but its use must be enabled at run-time by calling ESMF_MeshSetMOAB(). When MOAB is activated, the following new capabilities are supported in this release:
The Mesh creation, conservative regridding, and bilinear regridding algorithms when MOAB is active have been optimized to reduce their memory use and expand the size of Meshes they can be used on.
Grids can now be explicitly converted to a Mesh when MOAB is active, using the ESMF_MeshCreate() method.
Grids can be used to do first-order conservative regridding using MOAB.
Grids can be used for bilinear regridding on cell centers or corners using MOAB.""

[rokuingh]

@Plantain I believe the xESMF development has moved to a fork in the pangeo organisation. There are a few significant optimisations that are a result of the new MOAB back end to the ESMF Mesh, particularly with respect to memory. However, the flag to toggle this functionality has not yet been added to ESMPy (the ESMF Python interface that is the back end to xESMF). If you would like this functionality, it would probably be best to submit a feature request to both ESMF and the pangeo xESMF fork.