國立臺灣師範大學資訊教育研究所Chang, K. E.Jyu, H. F.Feng, W. S.2014-10-302014-10-301989-07-010010-4485http://rportal.lib.ntnu.edu.tw/handle/20.500.12235/34303The previous constrained via minimization problem for VLSI previous three-layer routing is the problem of deining which previous layers can be used for previous routing the wire segments in the interconnections of nets so that the number of previous vias is minimized. This problem has been shown to be NP-complete15. In this paper, this problem is first transformed to the contractibility problem of a previous three -colourable graph, then an heuristic algorithm is proposed on the basis of the graph contractability model. From experimental results, the algorithm proves faster and more efficient at generating very good results. For a typical case, the number of previous vias can be reduced by about 30%.computer-aided designVLSI designvia minimizationlayerassignmentgraph contractibilityConstrained via minimization for three-layer routing