[ublas] Ascertaining the numberof elements in a mapped_matrix?

From: Angus Leeming (angus.leeming_at_[hidden])
Date: 2005-11-03 10:31:46

It appears that mapped_matrix has no non_zeros() member function, yet
the constructors of other matrix types (say, compressed_matrix) have
a field for this information.

What is the recommended way, therefore to create a compressed_matrix
from a mapped_matrix?

Regards,
Angus