Effects of Nondeterminism in Hardware and Software Simulation with Thread Mapping

Abstract

In this paper, we explore the simulation performance trade-off under the lens of Monte Carlo design space exploration for multi-threaded programs and thread mapping. The vehicle used for this exploration will be a recent study, whose novel Google PageRank-based thread mapping approach is compared to hundreds of random mappings, as well as a Round-Robin-based thread mapping approach proposed in this paper used in similar comparisons. The modern simulator landscape presents a choice between cycle-accurate but slow, and fast but inaccurate program simulation. We find that the use of a fast, inaccurate multi-threaded simulator, such as Sniper 5.3, suffers from large nondeterminism in the reported performance of the program. We perform cycle-accurate simulation which demonstrates that the static thread mapping approach does provide benefits in reaching near-optimal design points. Furthermore, the runtime of static thread mapping is significantly reduced using a cycle-accurate simulator compared to the full Monte Carlo exploration of mapping design points.

Multilevel simulation-based co-design of next generation HPC microprocessors

“…On the other hand, DDR controllers placement does not seem to have a significant Besides, no conclusive behavior could be extracted from the water nsquared benchmark. This application suffers from non-determinism [43]. Indeed, while the number of memory reads/writes remains almost the same across multiple runs, the number of generated packets varies from simple to fourteenfold due to coherency protocols.…”