Simulated isobaric annealing

A simulated annealing algorithm for wire placement is proposed in which annealing is carried out under conditions of constant interconnection pressure rather than constant area. This is achieved by modifying the Metropolis criterion so that changes in the Gibbs free energy of the wires are calculated. This enables the area of the array devoted to wiring to decrease as the average wire length is reduced during the annealing schedule. The definition of interconnection pressure follows naturally from the thermodynamic interpretation of simulated annealing and it is shown to be equivalent to a wiring figure of merit called the channel density. The paper ends by speculating on the use of wire pressure to determine the phase transition temperature between the “gas” and “liquid” state of the system