the invention is directed to optimization of an initial routing that connects nets on a surface , each of the nets including plural interconnected net pins . the surface is divided into a set of areas , and a boundary pin is defined at each point on a boundary of one of the areas where the boundary of the one of the areas intersects a net . routing optimization is then performed in at least one of the areas , the routing optimization optimizing the routing among the net pins and the boundary pins within the at least one of the areas . the invention is also directed to optimization of an initial routing that connects nets on a surface , each of the nets including plural interconnected net pins . the surface is divided into a first set of pre - defined areas , and routing optimization is performed independently in each of the pre - defined areas in the first set . the surface is divided into a second set of pre - defined areas , and routing optimization is performed independently in each of the pre - defined areas in the second set . it is a feature of this aspect of the invention that each of plural pre - defined areas in the first set overlaps at least two pre - defined areas in the second set , and each of plural pre - defined areas in the second set overlaps at least two pre - defined areas in the first set .