A compilation technique for varying communication cost NUMA architectures

Abstract

In an earlier work, a Threshold Scheduling Algorithm was proposed to schedule the functional parallelism in a program on distributed memory systems. In this work, we address the issue of regeneration of the schedule for a set of distributed memory architectures with different communication costs. A new concept of dominant edges of a schedule is introduced to denote those edges which dictate schedule regeneration due to the changes in their communication costs. It is shown that under certain conditions, schedule on the whole or at least part of the graph can be reused for a different architecture reducing the cost of program re-partitioning and re-scheduling. The usefulness of this method is demonstrated by incorporating it in the scheduler of the compiler backend for targeting Sisal (Streams and Iterations in a Single Assignment Language) on a family of Intel i860 architectures: Gamma, Delta and Paragon which vary in their communication costs. It is shown that almost 30 to 65 % of the schedule can be reused, thereby, avoiding program re-partitioning to a large degree.

The authors gratefully acknowledge the support of Lawrence Livermore National Laboratory for allowing the use of Sisal compiler source code