A Preprocessor for the Via Minimization Problem

The objective of the via minimization is to assign wire segments into different layers to minimize the number of vias required. Several algorithms have been proposed for the Constrained Via Minimization (CVM) problem where the topology of the given layout is fixed. In a CVM problem, some vias may be "essential" to the given layout. That is, they have to be selected and cannot be replaced by other vias. In this paper we present a procedure to find most of the essential vias. This procedure can be used as a preprocessor for the algorithms for CVM problems. Experimental results show that the procedure is efficient and can identify most of essential vias.