An Algorithm for Searching Shortest Path by Propagating Wave Fronts in Four Quadrants

This paper discusses a new algorithm for searching the shortest path in VLSIs by propagating wave fronts in four quadrants. The algorithm has been experimentally programmed in FORTRAN IV on a Hitac M-200H computer. The main advantages of this algorithm are: 1. When there is a shortest path between two points, it can always be found by this algorithm; 2. In this algorithm, searching waves are divided into four quadrants. In each quadrant, waves advance or trace-back independently, according to their own rules. Therefore, in the algorithm only the current waves and the next set of waves need to be remembered, irrespective of their history. Thus much less memory (about 1/10~1/100) is required than for Lee's algorithm [1] 3. During searching for a shortest path in this algorithm, only segments currently defined need to be investigated. This greatly cuts down operation time, when compared to for Lee's algorithm; 4. This algorithm may be more advisable than Lee's algorithm for application to multi-layer wiring.