Series-Parallel Cell Width Minimization

In 1978, Uehara and vanCleemput published their original paper introducing a new and area-efficient layout style, the one-dimensional functional cell, which we have discussed in Chapters 1 and 2 [Uv78]; Fig. 3.1 illustrates such an cell. They also defined the WR layout problem of Fig. 2.4 and presented a heuristic that attempts to solve it for practical-sized functional cells. Many other researchers have subsequently studied this problem, as we have seen. Some have proposed heuristic solutions to the WR problem, while others have developed algorithms and heuristics for related problems. But no prior methods solve the WR problem exactly as originally proposed.