|  | mat | - the matrix | 
|  | m | - number of local rows (Cannot be PETSC_DECIDE) | 
|  | n | - This value should be the same as the local size used in creating the
x vector for the matrix-vector product y = Ax. (or PETSC_DECIDE to have
calculated if N is given) For square matrices n is almost always m. | 
|  | M | - number of global rows (or PETSC_DETERMINE to have calculated if m is given) | 
|  | N | - number of global columns (or PETSC_DETERMINE to have calculated if n is given) | 
|  | Ii | - row indices; that is Ii[0] = 0, Ii[row] = Ii[row-1] + number of elements in that row of the matrix | 
|  | J | - column indices | 
|  | v | - matrix values |