Horizontal Mesh

The Omega horizontal mesh uses the MPAS Mesh Specification. A mesh object is created by the init method, which assumes that Decomp has already been initialized.

OMEGA::Decomp::init();
OMEGA::HorzMesh::init(ModelClock);

The model clock should be the ocean model clock and is required by the IOStream routines that read the HorzMesh variables from the input stream HorzMeshIn. The constructor replicates the subdomain mesh cell/edge/vertex counts and connectivity information from Decomp so this information can be passed among the computational routines, alongside the other local mesh information. It then reads most of the remaining mesh variables (coordinates, lengths, areas) from the input HorzMeshIn IOStream. A few variables, like masks and operator scaling are computed internally. After reading, the init routine fills all halos and synchronizes the host and device copies of the mesh variables. These tasks are organized into several private methods. Eventually, dependent mesh variables will be computed from the minimum set of required mesh information.

After initialization, the default mesh object can be retrieved via:

OMEGA::HorzMesh *HMesh = OMEGA::HorzMesh::getDefault();

Once this retrieval has been performed, public member variables can be accessed using:

OMEGA::I4 NCellsOwned = HMesh->NCellsOwned;
OMEGA::Array1DR8 AreaCell = HMesh->AreaCell;

The HorzMesh is meant to be a container that allows the mesh information to be passed to the PDE solver routines:

void computeFluxTendency(OMEGA::HorzMesh *HMesh, ...) {
OMEGA::parallelFor({HMesh->NCellsOwned,HMesh->MaxEdges},
                      KOKKOS_LAMBDA (int Cell, int Edge) {
  if (Edge < HMesh->NEdgesOnCell(Cell)) {
      Var(Cell) = Var(Cell) + Flux(Cell,Edge);
  }
}

For member variables that are host arrays, variable names are appended with an H. Array variable names not ending in H are device arrays.

The device arrays are deallocated by the HorzMesh::clear() method, which is necessary before calling Kokkos::finalize. Because Field and IOStream also have references to HorzMesh variables, the IOStream::clear() and Field::clear() should also be called to ensure all device arrays are removed.