A provably good multilayer topological planar routing algorithm in IC layout designs

Abstract

Given a number of routing layers, the multilayer topological planar routing problem is to choose a maximum (weighted) set of nets so that each net in the set can be topologically routed entirely in one of the given layers without crossing other nets. This problem has important application in the layout design of multilayer IC technology, which has become available recently. In this paper, we present a provably good approximation algorithm for the multilayer topological planar routing problem. Our algorithm, called the iterative-peeling algorithm, finds a solution whose weight is guaranteed to be at least 1 − e 1 ∼ ∼ 63.2% of the weight of an optimal solution. The algorithm works for multi-terminal nets and arbitrary number of routing layers. For fixed number of routing layers, we have even tighter performance bounds. In particular, the performance-ratio of the iterative-peeling algorithm is at least 75% for two layer routing, and is at least 70.4% for three layer routing. Experimental results confirm that our algorithm can always route majority of the nets without using vias even when the number of routing layers is fairly small.

Escaped Boundary Pins Routing for High-Speed Boards

“…Despite the similarity to topological routing in [2], the major difference is that our approach is bus oriented. The proposed approach intends to route nets within a bus in a bunch in one layer by our CCP selection method, instead of taking net as an individual as [2] did.…”

“…We develop an against-the-wall routing for better preservation of routing resources for consequent routings. 2 Finally, we describe how we handle the inevitable crossing nets.…”

“…The proposed approach intends to route nets within a bus in a bunch in one layer by our CCP selection method, instead of taking net as an individual as [2] did. Under this premise, we generate DPS heuristically rather than exhaustively searching, as in [2]. …”

“…Considering the IR drop, crosstalk, and impedance matching, the net shape and the net length must be controlled based on certain criteria. Many original ideas have been created to solve these problems, such as in [2], [7], [14], [15], [20]. Reference [2] proposes a topological planar routing algorithm.…”

“…Many original ideas have been created to solve these problems, such as in [2], [7], [14], [15], [20]. Reference [2] proposes a topological planar routing algorithm. The BSG router [20] proposes an effective routing method.…”