subgraph name 属性必须要以cluster开头。

A Quick Introduction to GraphvizAn awesome tool for software documentation and visualizing graphshttps://www.worthe-it.co.za/blog/2017-09-19-quick-introduction-to-graphviz.html

 

digraph {rankdir="LR"// the normal ranking algorithm doesn't know what to// do with clusters with rank="same".// If you opt in to the 'new' ranking algorithm, it// works as expected.newrank="true"A -> BA -> CB -> CC -> Dsubgraph cluster_subs {label="Bs and Cs"rank="same"BC}
}