Title :
Effective free space management for cut-based placement via analytical constraint generation
Author :
Alpert, Charles J. ; Nam, Gi-Joon ; Villarrubia, Paul G.
Author_Institution :
IBM Corp., Austin, TX, USA
Abstract :
IP blocks and large macro cells are becoming more prevalent in the physical layout of a design, actually causing an increase in the available free space. We observe that top-down placement based on recursive bisection with multilevel partitioning performs poorly on these porous designs since it lacks a global view of the ideal placement. However, the strength of analytic placement methods lies in their ability to ascertain this global view. Consequently, we propose an enhancement to cut-based placement called analytic constraint generation (ACG). ACG utilizes an analytic engine to distribute available free space appropriately by determining balance constraints for each partitioning step. For one-dimensional placements, our experiments illustrate the large gap between analytic engines, traditional cut-based placement, and ACG as a design becomes increasingly sparse. We also show that for real industry designs, ACG significantly improves the performance of cut-based placement, particularly timing perspective, as implemented within a state-of-the-art industrial placer.
Keywords :
cellular arrays; circuit layout CAD; integrated circuit layout; logic CAD; logic partitioning; timing; analytic constraint generation; analytic engines; analytical constraint generation; available free space; balance constraints; cut-based placement; free space management; industrial placer; multilevel partitioning; one-dimensional placements; physical layout; porous designs; recursive bisection; timing perspective; top-down placement; Algorithm design and analysis; Analytical models; Constraint optimization; Design automation; Engines; Integrated circuit layout; Logic; Partitioning algorithms; Simulated annealing; Timing;
Journal_Title :
Computer-Aided Design of Integrated Circuits and Systems, IEEE Transactions on
DOI :
10.1109/TCAD.2003.818126