Sparse * Sparse without removing numerical zeros

Submitted by Christoph Hertzberg @chhtz

Assigned to Nobody

Link to original bugzilla bug (#284)
Version: 3.0

Description

When building a Sparse*Sparse product which is later decomposed it can be advantageous not to prune numerical zeros, so that the symbolical decomposition can be reused.

Moreover it might be possible to 'recompute' a Sparse*Sparse product where the structure did not change thus no overhead for reallocation would arise.