Modern floorplanning based on B*-tree and fast simulated annealing

Unlike classical floorplanning that usually handles only block packing to minimize silicon area, modern very large scale integration (VLSI) floorplanning typically needs to pack blocks within a fixed die (outline), and additionally considers the packing with block positions and interconnect constraints. Floorplanning with bus planning is one of the most challenging modern floorplanning problems because it needs to consider the constraints with interconnect and block positions simultaneously. In this paper, the authors study two types of modern floorplanning problems: 1) fixed-outline floorplanning and 2) bus-driven floorplanning (BDF). This floorplanner uses B^*-tree floorplan representation based on fast three-stage simulated annealing (SA) scheme called Fast-SA. For fixed-outline floorplanning, the authors present an adaptive Fast-SA that can dynamically change the weights in the cost function to optimize the wirelength under the outline constraint. Experimental results show that this floorplanner can achieve 100% success rates efficiently for fixed-outline floorplanning with various aspect ratios. For the BDF, the authors explore the feasibility conditions of the B^*-tree with the bus constraints, and develop a BDF algorithm based on the conditions and Fast-SA. Experimental results show that this floorplanner obtains much smaller dead space for the floorplanning with hard/soft macro blocks, compared with the most recent work. In particular, this floorplanner is more efficient than the previous works.