A fast algorithm for VLSI net extraction

Net extraction is crucial in VLSI design verification. Current algorithms for net extraction do not exploit the fact that the number, c, of different orientations of the line segments or polygon edges in a practical VLSI mask design is small relative to the number, n, of segments or edges. Instead, they rely on computing all intersections in the input and hence take time that is at least proportional to the number of intersections. In this paper we develop a simple and practical algorithm for net extraction that runs in O(cn log n) time and O(n) space, which is optimal for fixed c. Experiments indicate that the algorithm will generally outperform existing algorithms on practical VLSI designs. We expect that the techniques presented will be useful in other VLSI CAD problems that operate with restricted orientation geometries.