Section: Software and Platforms

Cl@k

Participants : Christophe Alias, Fabrice Baray [Mentor, Former post-doc in Compsys] , Alain Darte.

Cl@k (Critical LAttice Kernel) is a stand-alone optimization tool useful for the automatic derivation of array mappings that enable memory reuse, based on the notions of admissible lattice and of modular allocation (linear mapping plus modulo operations). It has been developed in 2005-2006 by Fabrice Baray, former post-doc Inria under Alain Darte's supervision. It computes or approximates the critical lattice for a given 0-symmetric polytope. (An admissible lattice is a lattice whose intersection with the polytope is reduced to 0; a critical lattice is an admissible lattice with minimal determinant.)

Its application to array contraction has been implemented by Christophe Alias in a tool called Bee (see Section  5.6 ). Bee uses Rose as a parser, analyzes the lifetimes of the elements of the arrays to be compressed, and builds the necessary input for Cl@k, i.e., the 0-symmetric polytope of conflicting differences. Then, Bee computes the array contraction mapping from the lattice provided by Cl@k and generates the final program with contracted arrays. More details on the underlying theory are available in previous reports. Cl@k can be viewed as a complement to the Polylib suite, enabling yet another kind of optimizations on polyhedra. Initially, Bee was the complement of Cl@k in terms of its application to memory reuse. Now, Bee is a stand-alone tool that contains more and more features for program analysis and loop transformations.