STANDARD CELL PLACEMENT USING SIMULATED SINTERING.

Abstract

Simulated annealing is a powerful optimization technique based on the annealing phenomenon in crystallization. A simulated sintering technique that is analogous to the sintering process in material processing is proposed. In sintering, the quality of a processed material is improved by heating it to a temperature close to the melting point. Analogously, it is shown that by starting out with a good initial configuration instead of a random configuration, and restricting uphill moves, simulated annealing can be sped up considerably. This idea is used for a standard cell placement program--GRIM in LTX2, an AT&T Bell Labs VLSI layout system. The initial configuration is produced either by changes to a layout the designer had done previously, or else by a fast program like Min-cut. Improvements of about 10% in chip area are obtained starting from a Min-cut placement, about three times faster than the simulated annealing program (which itself is several times faster than other well-known simulated annealing programs).