MATAIJSELL = "AIJSELL" - A matrix type to be used for sparse matrices. This matrix type is identical to MATSEQAIJSELL when constructed with a single process communicator,
and MATMPIAIJSELL otherwise. As a result, for single process communicators,
MatSeqAIJSetPreallocation() is supported, and similarly MatMPIAIJSetPreallocation() is supported
for communicators controlling multiple processes. It is recommended that you call both of
the above preallocation routines for simplicity.