## Section: Software

### Psyche

Participants : Mahfuza Farooque, Stéphane Graham-Lengrand [correspondant] .

Psyche (*Proof-Search factorY for Collaborative
HEuristics*) is a modular programme for universal proof-search
in classical logic. The motivation is twofold:

On the one hand, prove some mathematics of the broadest range while making the most of problem-specific techniques; On the other hand, gain high confidence about the correctness of the proofs produced without having to rely on a proof-checker.

The architecture is that of an interaction between a trusted universal kernel and smart plugins that are meant be efficient at solving certain kinds of problems:

The kernel contains the mechanisms for exploring the proof-search space in a sound and complete way, taking into account branching and backtracking. The output of Psyche comes from the (trusted) kernel and is therefore correct by construction. The plugins then drive the kernel by specifying how the branches of the search space should be explored, depending on the kind of problem that is being treated. The quality of the plugin is then measured by how fast it drives the kernel towards the final answer.

Version 1.0 of Psyche (released 4/9/2012) handles classical propositional logic, and its proof-search mechanism is simply the incremental construction of proof-trees in the polarised and focussed sequent calculus. The mechanism is driven by a plugin that emulates the behaviour of a SAT-solver (DPLL), with non-trivial features such as the eager application of the Unit Propagation rule, conflict analysis, backjumping and clause learning.

Psyche's input for that kind of SAT-problem is a file given in the standard DIMACS format.

See also the web page http://www.lix.polytechnique.fr/~lengrand/PSI/index.php?page=Psyche/index .