MCFRoute: A detailed router based on multi-commodity flow method

Detailed routing is an important stage in VLSI physical design. Due to the high routing complexity, it is difficult for existing routing methods to guarantee total completion without design rule checking violations (DRCs) and it generally takes several days for designers to fix remaining DRC-s. Studies has shown that the low routing quality partly results from non-optimal net-ordering nature of traditional sequential methods. In this paper, a novel concurrent detailed routing algorithm is presented that overcomes the net-order problem. Based on the multi-commodity flow (M-CF) method, detailed routing problem with complex design rule constraints is formulated as an integer linear programming (ILP) problem. Experiments show that the proposed algorithm is capable of reducing design rule violations while introducing no negative effects on wirelength and via count. Implemented as a detailed router following track assignment, the algorithm can reduce the DRCs by 38%, meantime, wirelength and via count are reduced by 3% and 2.7% respectively comparing with an industry tool. Additionally, the algorithm is adopted as an incremental detailed router to refine a routing solution, and experimental results show that the number of DRCs that industry tool can´t fix are further reduce by half. Utilizing the independency between subregions, an efficient parallelization algorithm is implemented that can get a close to linear speedup.