LINK x1 y1 x2 y2
mathematically links a “flying block” to the main data structure — (x1, y1) are the
coordinates of any point inside the flying block, and (x2, y2) are the coordinates of
any point inside the block that will provide the link to the flying block. This block
should be the one that is topologically closest to the flying block. (x1, y1) and (x2,
y2) should be chosen close to the blocks’ centroid locations to ensure correct linkage.
This command is not required if CONFIG cell is used.
请高人翻译一下上面这个命令，或直接解释一下link。谢谢
