DAG(有向无环图) ------应用

DAG是tree的泛化,也是ploy tree的泛化

 

In graph theory, polytree is a name for an oriented tree; that is, a polytree is a directed graph formed by giving a direction to each edge of a tree, forming an orientation of the tree. In other words, it
is a directed graph with exactly one directed path between any two vertices; equivalently, it is a directed acyclic graph (DAG) for which there are no undirected cycles and for which the underlying undirected graph is connected.

 

tree 是层次化，永远的细分，直到不能再分，DAG
从源开始细分，但是中间可以有合，有汇总。D就是可以合的点

上图是polytree
还不是通用的DAG  

 

DAG 在编译里用来基本块优化，重写序列排序时用，但是两个节点之间可以有同向的两条有向边   

操作系统中，多个进程之间的资源分配图为DAG，则多个进程是安全的

模型检测中，DAG存在有效的检测算法