There are even more constraints to adhere to in order to aggressively reduce the number of physical configurations, make sure to have a look at the paper for details, there are lots of cool tricks described there.

甚至还有更多的约束可以被添加到算法中，进而大幅削减实际的组合数目，你一定要看看这篇文章，里面有很多很酷的技巧。