Process independent constraint graph compaction

The author describes the DASL symbolic layout system, which is used to create experimental VLSI circuits. The DASL constraint graph compactor requires no user intervention to produce a process-independent design. It also produces results that are electrically correct, e.g., that control the placement of substrate contacts. In other constraint graph compaction if there is nothing to constrain an element's placement, it will slide as far to the left as possible. A technique has been developed that controls the size of the tubs and the placement of the substrate contacts. A given design can be recompacted for a new process, therefore without any user intervention being necessary. The substrate contact sliding problem is constrained by minimizing the area of the tubs in the unique fashion that is discussed.<>