A Plan Patching Approach to Switchbox Routing
We present a new AI approach to doing switchbox routing. Switchbox routing is the problem of connecting net terminals which are fixed on the boundaries of a rectangular routing area. It can be regarded as a planning problem in which the overall goal is to route the switchbox, and the individual subgoals are to route individual nets. The solution can then be called the completed “route-plan”. Switchbox routing is usually viewed as a constructive process based on a statically ordered set of heuristic rules, which is used to select the next net to route and to dictate how that net is to be routed. If the next net cannot be routed without conflict (overlapping nets in some track), the router quits in failure. Our approach starts at this point and is based on resolving such conflicts by patching the almost-correct route-plan. But this repair process can itself be regarded as a planning problem in which the overall goal is to resolve all of the conflicts, and the individual interacting subgoals are to correct individual conflicts. The solution can then be called the “patch-plan” which patches the route-plan. Because repair is formulated as a planning problem, the same planning architecture used to construct the route-plan can be used to construct the patch-plan. Therefore, we will use the architecture we have developed for our constructive PI-CAD ROUTER to build our reparative PI-CAD PATCHER. The result is a plan to patch another plan which is constructed in a situation-specific, interaction-sensitive manner.
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