UniRec: a unimodular-like framework for nested recursions and loops

Abstract

Scheduling transformations reorder operations in a program to improve locality and/or parallelism. There are mature loop transformation frameworks such as the polyhedral model for composing and applying instance-wise scheduling transformations for loop nests.In recent years, there have been efforts to build frameworks for composing and applying scheduling transformations for nested recursion and loops, but these frameworks cannot employ the full power of transformations for loop nests since they have overly-restrictive representations. This paper describes a new framework, UniRec, that not only generalizes prior frameworks for reasoning about transformations on recursion, but also generalizes the unimodular framework, and hence unifies reasoning about perfectly-nested loops and recursion.