A fast algorithm for minimizing FPGA combinational and sequential modules

We present a quadratic-time algorithm for minimizing the number of modules in an FPGA with combinational and sequential modules (like the C-modules and S-modules of the ACT2 and ACT3 architectures). The constraint is that a combinational module can be combined with one flip-flop in a single sequential module, only if the combinational module drives no other combinational modules. Our algorithm uses a minimum-cost flow formulation to solve the problem with a significant time improvement over a previous approach that used a general linear program.