Amount of storage allocated for nonzeros.
For a sparse matrix, NZMAX(S) is the number of storage locations
allocated for the nonzero elements in S.
For a full matrix, NZMAX(S) is prod(size(S)).
In both cases, nnz(S) <= nzmax(S) <= prod(size(S)).
See also NNZ , NONZEROS , SPALLOC .