119th Colloquium of Center for Computational Sciences

119th Colloquium

Title:Finding Regularity in Problems with Irregularity

Speaker:Dr. Hiroshi Nakashima
(Academic Center for Computing and Media Studies, Kyoto University, Professor)

Date: November 27, 2017 (Mon), Time: 10:00-11:30

Venue: Center for Computational Sciences, International Workshop Room

Language: Japanese


Vectorized computation especially on scalar processors with wide SIMD mechanism requires regularity. For example, though such a processor has gather/scatter capability for irregular memory accesses, they are much less efficient than ordinary consecutive accesses mainly due to, in speaker’s opinion, the line-oriented configuration of caches. Unfortunately, real HPC programs often have such irregular accesses to a vector multiplied to a sparse matrix in CRS format, to a linear list to represent a set of objects, and so on, and thus fail to exploit SIMD-vector mechanism efficiently. However, HPC problems (not programs) with sparse matrices, dynamically configured sets, etc. may have some degree of regularity because such objects can be represented in some form with regularity. In this talk, a few examples in which regularity is found and exploited are presented to discuss the importance of programming effort and of the way to reduce the amount of efforts made by programmers.

Coordinator :Taisuke Boku