The fanout problem: from theory to practice
Proceedings of the decennial Caltech conference on VLSI on Advanced research in VLSI
A heuristic algorithm for the fanout problem
DAC '90 Proceedings of the 27th ACM/IEEE Design Automation Conference
Performance-oriented technology mapping
Performance-oriented technology mapping
Bounding Fan-out in Logical Networks
Journal of the ACM (JACM)
Performance optimization under rise and fall parameters
ICCAD '99 Proceedings of the 1999 IEEE/ACM international conference on Computer-aided design
Design and analysis of physical design algorithms
Proceedings of the 2001 international symposium on Physical design
Efficient global fanout optimization algorithms
Proceedings of the 2001 Asia and South Pacific Design Automation Conference
Technology-based transformations
Logic Synthesis and Verification
Timing driven gate duplication: complexity issues and algorithms
Proceedings of the 2000 IEEE/ACM international conference on Computer-aided design
ICCD '00 Proceedings of the 2000 IEEE International Conference on Computer Design: VLSI in Computers & Processors
Timing driven gate duplication
IEEE Transactions on Very Large Scale Integration (VLSI) Systems
A Dual Dielectric Approach for Performance Aware Gate Tunneling Reduction in Combinational Circuits
ICCD '05 Proceedings of the 2005 International Conference on Computer Design
Speed indicators for circuit optimization
PATMOS'05 Proceedings of the 15th international conference on Integrated Circuit and System Design: power and Timing Modeling, Optimization and Simulation
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Fanout optimization is a fundamental problem in timing optimization. Most of the research has focussed on the fanout optimization problem for a single net (or the local fanout optimization problem LFO). The real goal, however, is to optimize the delay through the entire circuit by fanout optimization. This is the global fanout optimization (GFO) problem. Touati claims in his thesis [6] that visiting nets of the network in a reverse topological order (from primary outputs to inputs), applying the optimum LFO algorithm to each net, computing the new required time at the source and propagating the delay changes to the fanins yields a provably optimum solution to the GFO problem. This result implies that GFO is solvable in polynomial time if LFO is. In this paper, we show that that is not the case. We prove that GFO is NP-complete even if there are a constant number of buffering choices at each net. We analyze Touati's result and point out the flaw in his argument. We then present sufficient conditions for the optimality of the reverse topological algorithm.