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.

Err = OMEGA::Decomp::init();
Err = OMEGA::HorzMesh::init();

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 creates several parallel I/O decompositions and reads in the remaining subdomain mesh information. Finally, any mesh information needed on the device is copied from the host to a device Kokkos array. Arrays such as the coordinate variables, which are not involved in tendency calculations, are not transferred to the device. 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 copy from host to device array is performed in the constructor via:

AreaCell = OMEGA::createDeviceMirrorCopy(AreaCellH);

The device arrays are deallocated by the HorzMesh::clear() method, which is necessary before calling Kokkos::finalize.