5 Mesh Ghosts

A ghost entity is a local, read-only copy of a real entity on another chunk. Ghosts are typically added to the boundary of a chunk to allow the real (non-ghost) elements at the boundary to access values across the processor boundary. This makes a chunk ``feel'' as if it was part of a complete unpartitioned mesh; and can be useful with cell-centered methods, and in mesh modification.

Figure 4: A small mesh partitioned into two pieces.
Figure 5: The same mesh with one layer of edge-adjacent ghosts.
Figure 6: The same mesh with one layer of node-adjacent ghosts.

In Figure 4, we begin with a small mesh partitioned into pieces on the left and right. In Figure 5, we have added ghost elements (dark hashing) that share an edge with adjacent real elements (light hatching). In Figure 6, we add ghost elements that share at least one node with adjacent real elements.