Section: New Software and Platforms

ML-Sundials

Participants : Timothy Bourke, Jun Inoue, Marc Pouzet [contact] .

Sundials/ML is a comprehensive OCaml interface to the Sundials suite of numerical solvers (CVODE, CVODES, IDA, IDAS, KINSOL). Its structure mostly follows that of the Sundials library, both for ease of reading the existing documentation and for adapting existing source code, but several changes have been made for programming convenience and to increase safety, namely:

• solver sessions are mostly configured via algebraic data types rather than multiple function calls;

• errors are signalled by exceptions not return codes (also from user-supplied callback routines);

• user data is shared between callback routines via closures (partial applications of functions);

• vectors are checked for compatibility (using a combination of static and dynamic checks); and

• explicit free commands are not necessary since OCaml is a garbage-collected language.

OCaml versions of the standard examples usually have an overhead of about 50% compared to the original C versions, and almost never more than 100%.

The current version of Sundials/ML comprises about 30,000 lines of OCaml (plus 10,000 lines of api documentation) and 12,000 lines of C (plus 1000 lines of commentary). In comparison to our previous development (called ML-Sundials), the current version includes a major rewrite of the `nvector' interface to allow easier generalisation to parallel and custom vectors (both of which have now been implemented), a rewrite of the linear solver interfaces, a redesign of the linear solver interface (now including the ability to specify linear solvers in OCaml), and the inclusion of the CVODES and IDAS solvers.

Sundials/ML allows the use of the state-of-the-art Sundials numerical simulation library from OCaml programs. We use it within PARKAS for the Zélus compiler (documented elsewhere) and our ongoing experiments with Modelica. The binding is, however, complete and general purpose. It can potentially replace the less complete libraries underlying three or four open source projects.

The Sundials/ML source code has now been released under a BSD-3 license. It is available on github and through opam .