This repository contains fortran90 modules for the solution of stiff, linear, first order initial value problems. The routines are based on a linearised version of the RadauIIA described in Hairer & Wanner. They numerically solve the initial value problem y' = Ay with given initial conditions.

• [MUMPS] (https://mumps.enseeiht.fr/)

An example makefile is provided. You'll first need to compile MUMPS and link the radau code to your MUMPS installation afterwards.

All versions of the radau integrator use the assembled data format to provide the matrix to MUMPS. This format uses three arrays: one for the nonzero values of the matrix, one for the row indices and one for the column indices. Some basic matrix I/O routines are also provided.