LogP: towards a realistic model of parallel computation

TLDR

Existing parallel computation models are either overly simplistic or too specific, leading to exploitation of formal loopholes rather than practical performance across diverse machines. The authors introduce LogP as a model that captures key technology trends to provide a foundation for developing fast, portable parallel algorithms and guidance for machine designers. LogP is defined by four parameters—computing bandwidth, communication bandwidth, communication delay, and coupling efficiency—and its usefulness is illustrated with examples implemented on the CM‑5.

Abstract

A vast body of theoretical research has focused either on overly simplistic models of parallel computation, notably the PRAM, or overly specific models that have few representatives in the real world. Both kinds of models encourage exploitation of formal loopholes, rather than rewarding development of techniques that yield performance across a range of current and future parallel machines. This paper offers a new parallel machine model, called LogP, that reflects the critical technology trends underlying parallel computers. it is intended to serve as a basis for developing fast, portable parallel algorithms and to offer guidelines to machine designers. Such a model must strike a balance between detail and simplicity in order to reveal important bottlenecks without making analysis of interesting problems intractable. The model is based on four parameters that specify abstractly the computing bandwidth, the communication bandwidth, the communication delay, and the efficiency of coupling communication and computation. Portable parallel algorithms typically adapt to the machine configuration, in terms of these parameters. The utility of the model is demonstrated through examples that are implemented on the CM-5.