From functional to imperative: combining destination-passing style and views

Abstract

Programming in low-level imperative languages provides good performance but is error-prone. On the other hand, functional programs are usually free from low-level errors but performance suffers from costly programming abstractions. Compiling high-level functional programs into highperformance imperative still remains an open challenge.This paper presents an approach to compiling a high-level array-based functional IR (Intermediate Representation) into high-performance imperative code. It combines the existing work on DPS (Destination-Passing Style) with the Lift views system by extending the notion of view to destinations. Destination views can be seen as lazy operations that work in reverse; the lazy operations affect how data is being produced into memory, rather than how data is being consumed.This approach produces imperative code that existing techniques are unable to produce. The code produced outperforms the existing DPS approach on real-world workloads when targeting CPU code. The paper also demonstrates how destination views can be used to generate high-performance stencil code on GPUs (Graphics Processing Units), by encoding the 2.5D tiling optimization in a functional style.CCS Concepts: • Software and its engineering → Source code generation.