Optimal Constraint Graph Generation Algorithm for Layout Compaction Using Enhanced Plane-Sweep Method


IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E76-A   No.4   pp.507-512
Publication Date: 1993/04/25
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Discrete Mathematics and Its Applications)
computer aided design,  LSI design technology,  layout design,  compaction,  plane-sweep method,  

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This paper presents an optimal constraint graph generation algorithm for graph-based one-dimensional layout compaction. The first published algorithm for this problem was the shadow-propagation algorithm. However, without sophisticated implementation of a shadow-front, complexity of the algorithm could fall into O(n2), where n is the number of layout objects. Although our algorithm, called the enhanced plane-sweep based graph generation algorithm, is an extension of the shadow-propagation algorithm, such a drawback is resolved by introducing an enhanced plane-sweep technique. The algorithm maintains multiple shadow-fronts simultaneously by storing them in a work-list called previous-boundary. Since a balanced search tree is selected for implementation of the worklist, total complexity of the algorithm is O(n log n) which is optimal. Experimental results show that the enhanced plane-sweep based graph generation algorithm runs in almost linear time with respect to the number of layout objects and is faster than the perpendicular plane-sweep algorithm which is also optimal in terms of time complexity.