A new flow algorithm is described on the basis of the primal-dual method, which is to be adopted dedicatedly for the regeneration of optimal layouts for functional cells of the standard-cell level. In advance of discussing this main theme, the present paper first outlines a practical scheme of reusing those layouts which have been once generated for functional cells in an old fabrication technology, and then formulates an optimization problem for regenerating optimal layouts of functional cells under the constraints incurred by the renewal of design rules. An efficient algorithm proposed here aims at solving this optimization problem with the use of solution concepts for the minimum cost flow problem. A part of experimental results is also shown, which indicates that the proposed altorithm is the fastest for this optimization problem.

When a new fabrication process is set up, especially in layout design for functional cells, of practical importance is how to make the best use of layout resources so far accumulated in old fabrication processes. Usually layout data of each element are expressed mostly in terms of positional coordinate values, and hence it is extremely tedious to modify them at every change of design rules for a new fabrication technology. To cope with this difficulty, the present paper describes an automatic recycling scheme for layout resources accumulated dedicatedly for functional cell generation. The main subject of this scheme is to transform given layout data into a layout description format expressed in layout parameters. Once layout data are parameterized, layout patterns of functional cells can be reconstructed simply by tuning up parameters in accordance with a new set of design rules. A part of implementation results are also shown.