Showing papers on "Constraint graph (layout) published in 1991"
01 Jun 1991
TL;DR: A new algorithm for over-the-cell channel routing in the standard cell design technology using the two-layer routing model, called WISER, which considers longest paths in the vertical constraint graph as well as channel density as a basis for choosing nets to route over the rows of standard cells.
Abstract: In this paper, we present a new algorithm, called WISER, for over-the-cell channel routing in the standard cell design technology using the two-layer routing model. The novelty of our approach lies in use of “vacant” terminals for over-the-cell routing. Furthermore, we consider longest paths in the vertical constraint graph as well as channel density as a basis for choosing nets to route over the rows of standard cells. Our approximation algorithm for net selection produces provably good results. Algorithm WISER has been tested on several benchmark examples, and experimental results show that WISER reduces the channel height by an average of 29% as compared to conventional channel routers. In addition, it reduces the total number of vias by 32% in the average case.
45 citations
11 Nov 1991
TL;DR: The authors consider both the maximum cliques in the horizontal constraint graph and the longest paths in the vertical constraint graph as a basis for choosing the nets to route over the cells and prove that their net selection algorithm is guaranteed to produce a solution within 68% of the optimum.
Abstract: The authors present a novel algorithm for three-layer, over-the-cell channel routing of standard cell designs. The novelty of the proposed approach lies in the use of 'vacant' terminals for over-the-cell routing. Furthermore, the authors consider both the maximum cliques in the horizontal constraint graph and the longest paths in the vertical constraint graph as a basis for choosing the nets to route over the cells. They prove that their net selection algorithm is guaranteed to produce a solution within 68% of the optimum. The proposed algorithm has been implemented and tested on several benchmark examples. For the entire PRIMARY 1 benchmark, they reduce the total routing height by 76% as compared to a two-layer channel router, which leads to a 7% reduction in chip height. >
27 citations
11 Nov 1991
TL;DR: A hierarchical pin permutation algorithm is presented which is used as a preprocessor of conventional channel routing algorithms such that the results of the subsequent channel routing can be significantly improved.
Abstract: A hierarchical pin permutation algorithm is presented which is used as a preprocessor of conventional channel routing algorithms. This algorithm determines the proper positions of permutable gates and cell terminals such that the results of the subsequent channel routing can be significantly improved. First, gates and terminals are interchanged to maximize the number of aligned terminal pairs and to reduce the channel density. Then, terminals that are not aligned are interchanged to remove cyclic constraints in the vertical constraint graph (VCG). Experimental results show that the proposed algorithm considerably reduces the number of tracks and vias. >
9 citations
01 Jan 1991
TL;DR: Computer-aided synthesis of digital circuits from behavioral specifications offers an effective means of dealing with the increasing complexity of digital hardware design.
Abstract: Computer-aided synthesis of digital circuits from behavioral specifications offers an effective means of dealing with the increasing complexity of digital hardware design. The benefits of such a methodology include shortened design time to reduce design cost, ease of modification of the hardware specifications to enhance design reusability, and the ability to more effectively and completely explore the different design tradeoffs between area of the resulting hardware and its processing time.
7 citations
04 Jan 1991
TL;DR: The authors present an algorithm for the HVH.
Abstract: The authors present an algorithm for the HVH. . .VH multi-layer channel routing problem. First they determine the net groups to be positioned on the same track using a left-edge algorithm. The vertical constraint graph made from these net groups may contain many cycles. There is an attempt to remove the cycles through proper layer assignment and maze routing. >
1 citations