A proper model for the partitioning of electrical circuits

Partitioning algorithms for electrical circuits are often based on the heuristic manipulation of a simple element-toelement interconnection matrix. However, the element-to-element interconnection matrix does not properly represent an electrical interconnection, or "net", among more than two elements. This paper expands on several aspects of the discrepancy: i) its source, 2) the circumstances under which it is likely to be significant, and its magnitude for typical circuits, and 3) the comparative difficulty and expense of using a more appropriate representation. A physically correct "net-cut" model is presented. This model is computationally straightforward and is easily adapted to the typical heuristic solution strategies. The "net-cut" model is coupled with the Kernighan-Lin partitioning algorithm [3]; using the same algorithm, comparisons with the "edge-cut" model demonstrate that the correct model reduces net-cuts by 19 to 50% for four digital logic circuits.