Cell overlap is removed from rows during a cell placement procedure for an integrated circuit chip. The rows are partitioned into subrows so that cells in each subrow have a common characteristic vector. Cell overflow is removed from each of the subrows by moving a cell of an overflowed row or exchanging two cells, at least one of which is in the overflowed subrow. The half-cells of the dual height cells are moved to cell positions in a suitable pair of rows based on a calculated movement penalty. The movement is accomplished to align the half-cells and minimize the penalty. In preferred embodiments, the process is carried out by a computer under control of a computer program.