Number of non zero entries of a Matrix.

[Former user]

I think that a new method which returns the number of non zero entries of a Matrix could be useful, especially because the method data() isn't implemented. We have discussed about the problem here http://fenicsproject.org/qa/769/sparse-matrix-in-dolfin-with-c

[Prof Garth Wells]

See http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatGetInfo.html for PETSc, and http://trilinos.org/docs/r11.8/packages/tpetra/doc/html/classTpetra_1_1CrsGraph.html#a8128f053b0a2be163764825a9c855877 for Tpetra.

[Prof Garth Wells]

Add function GenericMatrix::nnz() to get number of non-zeros in matrix.

Fixes Issue #110

→ <<cset 0dba7ade1921>>

[Prof Garth Wells]

Removing milestone: 1.5 (automated comment)