Large-scale nonlinear optimization in circuit tuning

Circuit tuning is an important task in the design of custom digital integrated circuits such as high-performance microprocessors. The goal is to improve certain aspects of the circuit, such as speed, area, or power, by optimally choosing the widths of the transistors. This task can be formulated as a large-scale nonlinear, nonconvex optimization problem, where function values and derivatives are obtained by simulation of individual gates. This application offers an excellent example of a nonlinear optimization problem, for which it is very desirable to increase the size of the problems that can be solved in a reasonable amount of time. In this paper we describe the mathematical formulation of this problem and the implementation of a circuit tuning tool. We demonstrate how the integration of a novel state-of-the-art interior point algorithm for nonlinear programming led to considerable improvement in efficiency and robustness. Particularly, as will be demonstrated with numerical results, the new approach has great potential for parallel and distributed computing.