## Section: New Software and Platforms

### Psyche

Participants : Stéphane Graham-Lengrand [correspondant] , Assia Mahboubi, Jean-Marc Notin.

Psyche (*Proof-Search factorY for Collaborative HEuristics*) is a
modular proof-search engine whose first version, 1.0, was released in
2012:

http://www.lix.polytechnique.fr/~lengrand/Psyche/

The engine implements the ideas developed in the section “Trustworthy implementations of theorem proving techniques” above, and was the object of the system description [56] .

Psyche's proof-search mechanism is simply the incremental construction of proof-trees in the polarized and focused sequent calculus. Its architecture organizes 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 how fast it drives the kernel towards the final answer.

In 2014, major developments were achieved in Psyche, whose version 2.0 was released on 20th September 2014. It is now equipped with the machinery to handle quantifiers and quantifier-handling techniques. Concretely, it uses meta-variables to delay the instantiation of existential variables, and constraints on meta-variables are propagated through the various branches of the search-space, in a way that allows local backtracking. The kernel, of about 800 l.o.c., is purely functional.