Hi Henning, I just noticed https://hackage.haskell.org/package/hmatrix-banded. I have just made a PR to hmatrix to add a tridiagonal solver: https://github.com/albertoruiz/hmatrix/pull/224. I don’t think there is anything to do but I thought it worth sharing. Dominic Steinitz dominic at steinitz.org http://idontgetoutmuch.wordpress.com