GI Software with fewer Data Cache Misses

Résumé : By their very name caches are often overlooked and yet play a vital role in the performance of modern and indeed future hardware. Using MAGPIE (Machine Automated General Performance Improvement via Evolution of software) we show genetic improvement GI can reduce the cache load of existing computer programs. Operating on lines of C and C++ source code using local search, Magpie can generate new functionally equivalent variants which generate fewer L1 data cache misses. Cache miss reduction is tested on two industrial open source programs (Google's Open Location Code OLC and Uber's Hexagonal Hierarchical Spatial Index H3) and two 2D photograph image processing tasks, counting pixels and OpenCV's SEEDS segmentation algorithm. Magpie's patches functionally generalise. In one case they reduce data misses on the highest performance L1 cache dramatically by 47 percent.