Robust Performance Optimization Using Padding Nodes and Separator Sets

Yutaka TAMIYA  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E84-A   No.11   pp.2739-2745
Publication Date: 2001/11/01
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on VLSI Design and CAD Algorithms)
Category: Timing Analysis
timing optimization,  separator set,  network flow algorithm,  

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In this paper we present two contributions for a set of local transformations (a selection set) to improve a performance of a very large circuit. The first contribution is an idea of "padding node" and "multi-separator-set. " We have proven that combination of padding node and multi-separator-set provides the optimum selection set. The second contribution is our heuristic method to find a semi-optimum multi-separator-set, which uses a network flow algorithm. Our method is robust for very large circuits, because its memory usage and calculation time are linear and polynomial order with the size of the circuit. We have compared our method with Singh's selection function method, which provides the optimum selection set and is the best method in literature to date. Our method has successfully optimized delays of all circuits, while Singh's selection function method has aborted with three large circuits because of memory overflow. The results also has shown our method has a comparable capability in delay optimization to Singh's method, although our method is heuristic.