Sparse matrix assembly from sub-sparse matrices

Submitted by Gael Guennebaud @ggael

Assigned to Nobody

Link to original bugzilla bug (#1420)
Version: 3.4 (development)

Description

Assembling a large sparse matrix from several smaller ones is a very common task. This could be accomplished through the comma-initializer API or a more procedure API. In contrast to the desne world for which the sub matrices passed to operator comma are copied to the destination matrix on the fly, here operator comma would store references to each block (within a std::tuple?) and assemble the matrix at the end in a similar way than the kronecker-product implementation.

Patch welcome (with unit tests).

Depends on

#1433

Blocking

#1608