I received a bug report from someone who found that the gsl_spmatrix_set() function did not properly detect duplicate elements (ie it could set the same (i,j) matrix element to more than 1 value).
This was related to the linear array scheme I had originally implemented, which made it very infefficient to find duplicates (ie: a linear search was required each time). So I've changed the storage scheme for the triplet representation to a binary tree (specifically the AVL balanced binary tree). I took code from the GNU libavl library for the tree manipulation stuff. This actually makes a huge speed improvement in duplicate detection and element retrieval for large sparse matrices. There may however be a performance hit since a new tree node must be allocated each time an element is added to the matrix. But I believe the tradeoff is worth it. Anyone using gsl_spmatrix in their code will need to recompile since the binary format of that struct has changed. Patrick
