Optimal partitioners and end-case placers for standard-cell layout

We study alternatives to FM-based partitioning in the context of end-case processing for top-down standard-cell placement. The primary motivation is that small partitioning instances frequently contain multiple cells larger than the prescribed partitioning tolerance (balance constraint) and cannot be moved while preserving the legality of a solution. We focus on optimal partitioning and placement algorithms, based on either enumeration or branch-and-bound, that are invoked for instances below prescribed size thresholds, e.g., 10 cells for placement and 30 cells for partitioning. Such partitioners transparently handle tight balance constraints and uneven cell sizes while typically achieving 40 smaller cuts than the best of several FM starts for instances between 10 and 35 movable nodes. On such instances, branch-and-bound codes also achieve surprising speedups, on average, over single FM starts. Enumeration-based partitioners relying on Gray codes, while easier to implement and taking...

• Type: Conference
• Year: 1999
• Where: ISPD
• Authors: Andrew E. Caldwell, Andrew B. Kahng, Igor L. Markov
• Keywords: Hardware, ISPD 1999, Optimal Partitioning, Small Partitioning Instances, Top-down Standard-cell Placement