Using well-solvable minimum cost exact covering for VLSI clock energy minimization

To save energy of VLSI systems flip-flops (FFs) are grouped in Multi-Bit Flip-Flop (MBFF), sharing a common clock driver. The energy savings strongly depends the grouping. For 2-bit MBFFs the optimal grouping turns into a minimum cost perfect graph matching problem. For k-bit MBFFs the optimal grouping turns into a minimum cost exact k-covering problem. We show that due to their special setting that is based on the FFs' data toggling probabilities, those problems are well-solvable in O(nlogn) time complexity.