A new routing region definition and ordering algorithm are presented for building block layout consisting of rectangular blocks. In contrast to other works, this algorithm enables a router to deal with the channel intersections efficiently, while permitting the expansion of any region when being routed. Before this algorithm is run, it is assumed that proper routing space has been assigned between the circuit blocks, so that the expansion of a region does not greatly affect the general structure. The algorithm starts from the classic set of channels. Each channel is then decomposed into several rectangular regions. If N is the number of channels, there will be around 2N regions at the end of the process. A constraint graph defines the order in which the regions should be routed. Routing results are given to illustrate the efficiency of this new scheme.
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