Compacting dead space in partitioning methods for random cells placements

The partitioning methods for placement work by allocating cells to partition groups. The groups are then further partitioned until the number of cells allocated to each group is small enough to be handled efficiently by other placement methods. The authors introduce extended channel constraint (ECC) graphs, a concept extended from Lauther´s channel constraint graphs. The ECC graphs lead to a methodology for compacting and reorganizing dead space generated from the partitioning methods