Cell shifting aware of wirelength and overlap

The technique of cell shifting has the advantage of linearly smoothing the overlap in placement. In the shifting process we should preserve the integrity of the original placement as much as possible and do less damage to the relative locations of the cells. The current cell shifting methods only locally or globally smooth the density without considering the relation between the local and the global density. Furthermore, the cells generally are treated as points with area during cell shifting. In this paper we present a new cell shifting technique called CSAWO to smooth the density distribution. CSAWO obtains the shifting distance while considering the local and the global density distribution simultaneously. The density and wire length are taken into consideration while shifting the cells. We also separate the standard cells and the macro blocks crossing multi-bin, and give the cell shifting distance by summing the shifting vector of the discrete module so as to get a more smooth speed. CSAWO has been embedded into the global placement process of CPlace, experimental result shows that the average runtime and HPWL have reduced 78% and 7% respectively comparing to DPlace[9].