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LogP: Towards a Realistic Model of Parallel Computation

Culler, David
Karp, Richard
Patterson, David
Sahay, Abhijit
Schauser, Klaus Erik
Santos, Eunice
Subramonian, Ramesh
von Eicken, Thorsten
Technical Report Identifier: CSD-92-713
December 1992

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.

Keywords: massively parallel processors, parallel models, complexity analysis, parallel algorithms, PRAM.