NRG: global and detailed placement

Abstract

We present a new approach to the placement problem. The proposed approach consists of analyzing the input circuit and deciding on a two-dimensional global grid for that particular input. After determination of the grid size, the placement is carried out in three steps: global placement, detailed placement, and final optimization. We show that the output of the global placement can also serve as a fast and accurate predictor. Current implementation is based on simulated annealing. We have put all algorithms together in a placement package called NRG (pronounced N-er-G). In addition to area minimization, NRG can perform timing-driven placement. Experimental results are strong. We improve TimberWolf's results (version 1.2) by about 5%. Our predictor can estimate the wavelength within 10-20% accuracy offering 2-20x speedup compared with the actual placement algorithm.