Fixed-Outline Floorplanning: Block-Position Enumeration and a New Method for Calculating Area Costs

In this paper, we propose a fixed-outline floorplanning (FOFP) method [insertion-after-remove (IAR) FP]. An elaborated method for perturbing solutions, the IAR, is devised. This perturbation uses a technique of enumerating block positions, which is implemented based on the floorplan-representation sequence pair. The proposed perturbation method can greatly accelerate searching-based algorithms, such as simulated annealing, by skipping many solutions that fail to meet the fixed-outline constraint. Moreover, based on the analysis of the diverse objective functions used in the existing research works, we suggest for the FOFP a new objective function which is still effective when combined with other objectives. Experimental results show that, if area and wirelength are optimized simultaneously, using less time, the proposed method obtains much higher average success rate for the FOFP with various aspect ratios, while the wirelength with the fixed-outline constraint is reduced by 20% on average, compared with the latest fixed-outline floorplanners. On the other hand, we validated once more by experiments that an aspect ratio close to one is beneficial to wirelength, and hence, a larger area weight is necessary for the FOFP with a larger aspect ratio to ensure feasible solutions.