Re: Sparse Matrix math

["E. Robert Tisdale" <E dot Robert dot Tisdale at jpl dot nasa dot gov>]

Anis Ahmad wrote:

> Are there any plans to add support for Sparse Matrix math?
> There are already free libraries for that purpose (sparselib/iml).
> I thought it would be nice to see GSL including that area as well.

Why should the GSL provide sparse matrix math libraries
if there are already free libraries for that purpose?

Strictly speaking,
a sparse matrix is just a dense matrix with a lot of zeros in it.
The purpose of sparse matrix math library is to

    1. keep track of the non-zero elements and
    2. squeeze the zero elements out of the data representation
    to save storage space.

Consequently, sparse matrix math libraries are about
the actual representation of the data and
the actual implementation of the algorithms.
The problem is that there is no one best representation
or implementation for every application.