Patent ID: 6260179
Filing Date: 2001-07-10
Classification: G06F

Abstract:
A method for evaluating an arrangement of a multiplicity of cells, whose interconnection relationship is previously determined, in a predetermined region, which has been divided into a first grid by units of a minimum pitch of wiring, using a predicted wiring density among the arranged multiple cells in designing a circuit so that a multiplicity of wiring lines are routed along the first grid of the predetermined region to interconnect between the multiple cells in accordance with the interconnection relationship in a subsequent stage of the circuit designing, said method comprising the steps of:(i) dividing the predetermined region into a second grid of unit squares, each of the unit squares being a unit of prediction of the wiring density;(ii) selecting, for each of the multiple wiring lines, two cells having a pair of pins to be interconnected by each said wiring line from the arranged multiple cells;(iii) setting a rectangular region whose one diagonal pair of vertexes is the pair of pins of the two cells selected for each said wiring line;(iv) calculating, for each of intersections of the first grid which are situated within the rectangular region, a probability that each said wiring line is routed to pass through each said intersection within the rectangular region as a wiring-line passing probability, assuming that the wiring line passing probability is uniform at every intersection within the rectangular region;(v) calculating, for each of the unit squares of the second grid, a proportion of an area occupied by the rectangular region to an entire area of each said unit square as a rectangular region occupancy ratio;(vi) multiplying, for each said unit square, the wiring line passing probability for any intersection within the rectangular region by the rectangular-region occupancy ratio for each said unit square to thereby obtain a first wiring density influence value for each said unit square, said first wiring density influence value representing an increment of the wiring density caused by each said wiring line;(vii) totaling, for each said unit square, the first wiring-density influence values for all of the multiple wiring lines to thereby predict the wiring density of each said unit square; and(viii) evaluating the arrangement of the multiple cells based on the predicted wiring density in each said unit square.