# Sylvester Solver Change Log

Tag | Date | Description/Changes
| 2003/09/10 | Initial version solving triangular system put to repository
|  | Implemented solution of general case.
|  | Implemented a memory pool (Paris).
|  | Implemented MEX interface to the routine (Paris).
|  | Implemented QuasiTriangularZero (Paris) (not fully used yet).
rel-1 | 2003/10-02 | Version sent to Michel.
|  | Inheritance streamlined, QuasiTriangular inherits from GeneralMatrix.
|  | Implemented block diagonalization algorithm.
|  | Solution routines rewritten so that the output rewrites input, considerable memory improvement.
|  | MEX interface now links with LAPACK library from MATLAB.
|  | Added a hack to MEX library loading in order to avoid MATLAB crash in Wins.
rel-2 | 2003/10/15 | Version sent to Michel.
|  | KronUtils now rewrite input by output using less memory.
|  | Added iterative solution algorithm (doubling).
|  | Introduced abstraction for set of parameters (SylvParams).
|  | Algorithm enabled to solve problems with singular C.
|  | Implemented a class chooser chossing between QuasiTriangularZero, and QuasiTriangular (padded with zero) depending on size of the problem. Full use of QuasiTriangularZero.
|  | Reimplemented QuasiTriangular::solve, offdiagonal elements are eleiminated by gauss with partial pivoting, not by transformation of complex eigenvalues. More stable for ill conditioned eigenvalues.
|  | Reimplemented calculation of eliminating vectors, much more numerically stable now.
|  | Implemented algorithm for ordering of eigenvalues (not used now, no numerical improvements).
rel-3 | 2003/12/4 | Version sent to Michel.
|  | GeneralMatrix separated for use outside, in sylv module we use its subclass SylvMatrix. Implemented ConstGeneralMatrix (useful outside).
rel-4 | 2004/6/4 | Version, which was moved to pythie.cepremap.cnrs.fr repository.