Amdahl's law for predicting the future of multicores considered harmful

B.H.H. Juurlink; C. H. Meenderinck

doi:10.1145/2234336.2234338

$Amdahl s Law for Predicting the Future of Multicores Considered Harmful B.H.H. Juurlink Berlin University of Technology Berlin, Germany C.H. Meenderinck cor.meenderinck@intellimagic.net more complex problems. For example, more cores are used to perform weather forecasting on a larger area (e.g., [12]) or for video decoding with higher resolutions [3]. Furthermore, for many applications, when the problem size scales the parallel part scales faster than the serial part. Gustafson therefore proposed an alternative to Amdahl s law which is now known as Gustafson s law but which he himself attributed to E. Barsis. Gustafson s law is much more optimistic than Amdahl s law. While Hill and Marty brie y mention Gustafson s law, they state that in their view multicore designs should also operate well under Amdahl s more pessimistic assumptions and do not consider it further. The main contribution of this work is two-fold. First we generalize Amdahl s and Gustafson s laws by assuming that the parallel fraction does not stay constant as in Amdahl s law, nor that it grows linearly with the number of cores as in Gustafson s law, but something in between (e.g., it is proportional to n, where n is$

Amdahl's law for predicting the future of multicores considered harmful

Juurlink, B.H.H.; Meenderinck, C. H.

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