SingularValueDecomposition bug: fifty examples

*To*: mathgroup at smc.vnet.net*Subject*: [mg60753] SingularValueDecomposition bug: fifty examples*From*: John Sidles <sidles at u.washington.edu>*Date*: Tue, 27 Sep 2005 03:45:23 -0400 (EDT)*References*: <906C0B48-1EB7-403C-A2F4-ED8FEA05BE1F@u.washington.edu>*Sender*: owner-wri-mathgroup at wolfram.com

Dear Mathgroup folks I have documented fifty different examples of matrices for which SingularValueDecomposition[] fails under Mathematica 5.2 (Mac OS X, Tiger). Full details are here: http://faculty.washington.edu/sidles/mma_svd_failure_example/ README.pdf The matrices themselves (plus a notebook to successively load them and document the SVD failure) are in this gzipped tarball: http://faculty.washington.edu/sidles/mma_svd_failure_example/ SVDfailures.tar.gz A Makefile is included -- run "make unpack" to unpack the tarball: http://faculty.washington.edu/sidles/mma_svd_failure_example/ Makefile Just as a point of interest, the above files include: -> 25 matrices that generate the following (undocumented) error message: "SingularValueDecomposition::cfail: Algorithm failed to converge." -> 25 matrices for which SingularValueDecomposition[] returns a wrong result, with no error message. Needless to say, a call to SingularValueDecomposition[] should never fail ... our application (a terrain-following mapping program) surely depends on this! Sincerely John Sidles

**Follow-Ups**:**Re: SingularValueDecomposition bug: fifty examples***From:*Sseziwa Mukasa <mukasa@jeol.com>