IMF: interconnect-driven multilevel floorplanning for large-scale building-module designs

We present in this paper, a new interconnect-driven multilevel floorplanning, called IMF, to handle large-scale building-module designs. Unlike the traditional multilevel framework that adopts the "V-cycle" framework: bottom-up coarsening followed by top-down uncoarsening, in contrast, IMF works in the "Λ-cycle" manner: top-down uncoarsening (partitioning) followed by bottom-up coarsening (merging). The top-down partitioning stage iteratively partitions the floorplan region based on mm-cut bipartitioning with exact net-weight modeling to reduce the number of global interconnections and thus the total wirelength. Then, the bottom-up merging stage iteratively applies fixed-outline floorplanning using simulated annealing for all regions and merges two neighboring regions recursively. We also propose an accelerative fixed-outline floorplanning (AFF) to speed up wirelength minimization under the outline constraint. Experimental results show that IMF consistently obtains the best floorplanning results with the smallest wirelength for large-scale building-module designs, compared with all publicly available floorplanners. In particular, IMF scales very well as the circuit size increases. The Λ-cycle multilevel framework outperforms the V-cycle one in the optimization of global circuit effects, such as interconnection and crosstalk optimization, since the Λ-cycle framework considers the global configuration first and then processes down to local ones level by level and thus the global effects can be handled at earlier stages. The Λ-cycle multilevel framework is general and thus can be readily applied to other problems.