An effective congestion-based integer programming model for VLSI global routing

Global routing is a fundamental problem in VLSI physical design in which approximate paths for the interconnect (wires) of a circuit are decided. In this paper, a fast, order-free global routing technique is proposed by formulating the global routing problem as an integer linear programming (ILP) problem. A small set of high quality trees, in terms of congestion and length, for each net in the circuit is first produced. Then, a preprocessing technique is proposed to reduce problem sizes while maintaining solution quality. Evaluating performance on the IBM-place 2.0 suite shows a 19.5% average reduction in maximum channel capacity and a 71% average improvement in solving times compared to the traditional concurrent techniques. The proposed concurrent technique is also shown to be faster than the sequential router Labyrinth.