Hinted quad trees for VLSI geometry DRC based on efficient searching for neighbors

Abstract

Design-rule checking, whose efficiency depends greatly on the speed in finding an object's neighbors, is an indispensable component of any VLSI design process. Given a design, the objects it contains are usually represented by their smallest enclosing rectangles, and neighbor search is defined as the operation to find, among the collection of rectangles, the ones that are within the specified distance of a rectangle. Commonly, the rectangles are stored in a tree structure, and a region query that searches the tree starting at its root is used to find a rectangle's neighbors. In this paper, we introduce the hinted quad tree, or HQT, that supports neighbor searches directly without always starting a search at the root of the tree. We show that HQT achieves the highest neighbor-search performance among the data structures compared and uses a reasonable amount of storage.