Optimizing parallel PREM compilation over nested loop structures

Abstract

We consider automatic parallelization of a computational kernel executed according to the PRedictable Execution Model (PREM), where each thread is divided into execution and memory phases. We target a scratchpad-based architecture, where memory phases are executed by a dedicated DMA component. We employ data analysis and loop tiling to split the kernel execution into segments, and schedule them based on a DAG representation of data and execution dependencies. Our main observation is that properly selecting tile sizes is key to optimize the makespan of the kernel. We thus propose a heuristic that efficiently searches for optimized tile size and core assignments over deeply nested loops, and demonstrate its applicability and performance compared to the state-of-the-art in PREM compilation using the PolyBench-NN benchmark suite.