NBLG: A Robust Legalizer for Mixed-Cell-Height Modern Design

Abstract

With the increasing complexity of modern design, mixed-cell-height designs have become more popular, which makes the legalization problem more challenging. In this article, a robust negotiation-based legalizer (NBLG) is proposed to reduce average displacement and maximum displacement for mixed-cell-height circuits with considering the fence region and technology constraints. By dissecting the main components of the negotiation-based method, we divide the placement grid in terms of placement sites and reformulate the legalization problem as a resource allocation task. We then allow all movable cells to gradually remove overlaps in a surrounding window with two individual techniques: 1) isolation point and 2) adaptive penalty function. We also adopt a deterministic multithreading technique to accelerate the convergence of our algorithm. Experimental results show that our legalizer achieved the minimal average displacement and maximum displacement in a reasonable runtime compared with state-of-the-art methods.