Design Flow Parameter Optimization with Multi-Phase Positive Nondeterministic Tuning
Synthesis and place & route tools are highly leveraged for modern digital design. But, despite continuous improvement in CAD tool performance, products in competitive markets often set PPA (performance, power, area) targets beyond what the tools can natively deliver. These aggressive targets lead to circuit designers attempting to tune a vast number of design flow parameters in search of near-optimal design specific flow recipes. Compounding the complex design flow parameter tuning problem is that many digital design tools exhibit nondeterminism, i.e., run-to-run variation. While CAD tool nondeterminism is typically considered an undesirable behavior, this paper proposes design flow tuning methodologies that take advantage of nondeterminism. We propose techniques that employ a combination of running targeted scenarios multiple times to exploit positive deviations nondeterminism can produce and leverage the best observed runs as seeds for multi-phase tuning. We introduce three seed variants for multi-phase tuning that have a spectrum of characteristics, trading off PPA improvement and reduce run-to-run variation. Our experimental analysis using high-performance industrial designs show that the proposed novel techniques outperform an existing state-of-the-art industrial design flow tuning program across all PPA metrics. Furthermore, our proposed approaches reduce run-to-run variation of the best scenarios, leading to a more predictable design flow.