GPU Tensor Cores for fast Arithmetic Reductions

This work proposes a GPU tensor core approach that encodes the arithmetic reduction of n numbers as a set of chained m × m matrix multiply accumulate (MMA) operations executed in parallel by GPU tensor cores. The asymptotic running time of the proposed chained tensor core approach is T(n)=5 logm2n and its speedup is S=dfrac45 log2m2 over the classic O(n log n) parallel reduction algorithm. Experimental performance results show that the proposed reduction method is ~ 3.2 × faster than a conventional GPU reduction implementation, and preserves the numerical precision because the sub-results of each chain of R MMAs is kept as a 32-bit floating point value, before being all reduced into as a final 32-bit result. The chained MMA design allows a flexible configuration of thread-blocks; small thread-blocks of 32 or 128 threads can still achieve maximum performance using a chain of R=4,5 MMAs per block, while large thread-blocks work best with R=1. The results obtained in this work show that tensor cores can indeed provide a significant performance improvement to non-Machine Learning applications such as the arithmetic reduction, which is an integration tool for studying many scientific phenomena.