Minimizing channel density in standard cell layout

Blair, Jean R. S.; Kapoor, Sanjiv; Lloyd, Errol L.; Supowit, Kenneth J.

doi:10.1007/bf01840363

“…In fact, the problem of determining net segments itself is already NP-hard even for a small number of cell rows (assuming that no feedthroughs need to be added). To be more precise, we state the following theorem based on a result in [15]: Proof. First, let us look at a simplified net segment selection problem.…”

Section: Formulation Of the Problemmentioning

confidence: 99%

“…Therefore, the TLNR problem is a special case of the general net segment selection problem that we are interested. However, the TLNR problem was shown to be NP-hard if there are five or more cell rows in the design [15]. Thus, the net segment selection problem is NP-hard if there are five or more cell rows in the design.…”

Section: Formulation Of the Problemmentioning

confidence: 99%

A new algorithm for standard cell global routing

Cong

¹

,

Preas

²

1992

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Abstract. In this paper, we present a new algorithm for standard cell global routing. The algorithm considers all of the interconnection nets simultaneously; this produces superior results since information about all of the nets is available throughout the global routing process. Wc formulate the global routing problem as one of finding the optimal spanning forest on a graph that contains all of the interconnection information. The results of an important theorems allow us to prune many non-optimal connections before the global routing process begins. This approach successfully solves the net ordering and congestion prediction problems which other approaches suffer. The new algorithm was implemented as part of the DATools system at Xerox PARC. The benchmarks from the Physical Design Workshop are used as part of the comparison suite. The new algorithm achieves up to 11% area reduction compared to the previous global routing package used in the DATools system and obtains up to 17% reduction in the total channel density compared to the Timberwolf 4.2 package.

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“…Although [Bla87] has introduced an odd-even heuristic which is able to produce a solution within a factor of 1.5 of the optimal solution, that heuristic could only be applied to circuits where each net consists of two pins. Recently, a parallel global router for standard cell circuits called LocusRoute [Rod381 was reported.…”

Section: Introductionmentioning

confidence: 99%

A global router for sea-of-gates circuits

Lee¹,

Sechen²

Proceedings of the European Conference on Design Automation.

6

0

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we describe a new global routing algorithm designed SPeCifiCaY for sea-of-gates circuits. The algorithm has generalized to handle g: (~~t~o which seeks to even congestion, (3) a oveflows and reduces the congestion, (4) vertical track assignment, and (5) congestion evening at the detailed global routing level. ~n tests on the MCNC benchmark Circuits, the algorithm produced layouts with an average of 11% fewer routing tracks than the other algorithms. In tests on gate array benchmark circuits. the algorithm not only achieved uniform channel densities, but the maximum channel densities it produced are the lowest values that have ever been reported.types of hierarchical approaches: the topdown approach [Bur831 and the bottom-up approach [Mar84]. The basic principles behind these two different approaches are that all the ne6 are routed simultaneously at each hierarchical level, and the solutions at a hierarchical level are refined at the next hierarchical level. Hence, the problem of net-ordering is avoided. Hierarchical approaches Usually Suffer from difficulties with resolving the Seams between the set of subproblems on a given level of hierarchy. Constructive approaches have also been used in the global routing of gate arrays [Li84]. In Li's approach [Li84], based on the distribution of the pins and a congestion analysis, the global router first constructs the solutions at chip's periphery region and then proceeds inward. But this approach onlv seeks to route 100% of the nets and does not seek to minimize the total channel m e~d ,(2) a two-stage coacse global muting muting procedure which

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A new algorithm for standard cell global routing

Cong

¹

,

Preas

²

[1988] IEEE International Conference on Computer-Aided Design (ICCAD-89) Digest of Technical Papers

14

0

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Abstract. In this paper, we present a new algorithm for standard cell global routing. The algorithm considers all of the interconnection nets simultaneously; this produces superior results since information about all of the nets is available throughout the global routing process. Wc formulate the global routing problem as one of finding the optimal spanning forest on a graph that contains all of the interconnection information. The results of an important theorems allow us to prune many non-optimal connections before the global routing process begins. This approach successfully solves the net ordering and congestion prediction problems which other approaches suffer. The new algorithm was implemented as part of the DATools system at Xerox PARC. The benchmarks from the Physical Design Workshop are used as part of the comparison suite. The new algorithm achieves up to 11% area reduction compared to the previous global routing package used in the DATools system and obtains up to 17% reduction in the total channel density compared to the Timberwolf 4.2 package.

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Minimizing channel density in standard cell layout

Cited by 3 publications

References 14 publications

A new algorithm for standard cell global routing

A new algorithm for standard cell global routing

A global router for sea-of-gates circuits

A new algorithm for standard cell global routing

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