如何强制对点中的节点进行排名？

Question

我有许多 graphviz 点格式的相对简单（自动生成）的图表。 这些显示了通过状态机的路径，但 dot 有一个有点令人困惑的习惯，即当我希望图形按状态顺序排列时，它会决定两个节点必须处于同一等级。 我已经尝试了很多设置（包括下面列出的 :n 和 :s 以及 weight），但我无法说服 dot将第三状态置于第四状态之上。

我在很多图表上都遇到这个问题：似乎有一些内部的点决定如果两个节点处于同一等级并且没有什么可以覆盖它会更好。 我什至有代码指定一个节点应该是 rank=sink，但 dot 决定在其下面放置另一个节点。

有没有什么方法可以表明节点有序比任何其他约束更重要？

用于生成图表的代码如下所示：

digraph {
    ERROR [label="Error"];
    FirstSTATE [label="Initial State" URL="\ref FirstSTATE"];
    FirstSTATE -> SecondSTATE;
    SecondSTATE [label="Second State" URL="\ref SecondSTATE"];
    SecondSTATE -> ThirdSTATE;
    ThirdSTATE [label="Third State" URL="\ref ThirdSTATE"];
    FourthSTATE [label="Fouth State?" shape="diamond"];
    ThirdSTATE:s -> FourthSTATE:n [weight=50];
    FourthSTATE -> FifthSTATE [label="Yes" ];
    FourthSTATE -> ThirdSTATE [label="No"];
    FifthSTATE [label="Fifth State" URL="\ref FifthSTATE"];
    SixthSTATE [label="Sixth State?" shape="diamond"];
    SixthSTATE -> ERROR [label="Yes" ];
    SixthSTATE -> SeventhSTATE [label="No"];
    FifthSTATE -> SixthSTATE;
    SeventhSTATE [label="Seventh State" URL="\ref SeventhSTATE"];
    SeventhSTATE -> EighthSTATE;
    EighthSTATE [label="Eighth State" URL="\ref EighthSTATE"];
    NinthSTATE [label="Ninth State?" shape="diamond"];
    NinthSTATE -> TenthSTATE [label="Yes" ];
    NinthSTATE -> EighthSTATE [label="No"];
    EighthSTATE -> NinthSTATE;
    TenthSTATE [label="Tenth State" URL="\ref TenthSTATE"];
    EleventhSTATE [label="Eleventh State?" shape="diamond"];
    EleventhSTATE -> ERROR [label="Yes" ];
    EleventhSTATE -> TwelfthSTATE [label="No" ];
    TenthSTATE -> EleventhSTATE;
    TwelfthSTATE [label="Twelfth State" URL="\ref TwelfthSTATE"];
}

该图表当前如下所示：

Answer 1

使用“constraint=false”。

http://www.graphviz.org/doc/info/attrs.html #d:constraint

在你的图表中：

FourthSTATE -> ThirdSTATE [label="No" constraint=false] ;

你将得到：

digraph {
    ERROR [label="Error"];
    FirstSTATE [label="Initial State" URL="\ref FirstSTATE"];
    FirstSTATE -> SecondSTATE;
    SecondSTATE [label="Second State" URL="\ref SecondSTATE"];
    SecondSTATE -> ThirdSTATE;
    ThirdSTATE [label="Third State" URL="\ref ThirdSTATE"];
    FourthSTATE [label="Fouth State?" shape="diamond"];
    ThirdSTATE -> FourthSTATE;
    FourthSTATE -> FifthSTATE [label="Yes" ];
    FourthSTATE -> ThirdSTATE [label="No" constraint=false] ;
    FifthSTATE [label="Fifth State" URL="\ref FifthSTATE"];
    SixthSTATE [label="Sixth State?" shape="diamond"];
    SixthSTATE -> ERROR [label="Yes" ];
    SixthSTATE -> SeventhSTATE [label="No"];
    FifthSTATE -> SixthSTATE;
    SeventhSTATE [label="Seventh State" URL="\ref SeventhSTATE"];
    SeventhSTATE -> EighthSTATE;
    EighthSTATE [label="Eighth State" URL="\ref EighthSTATE"];
    NinthSTATE [label="Ninth State?" shape="diamond"];
    NinthSTATE -> TenthSTATE [label="Yes" ];
    NinthSTATE -> EighthSTATE [label="No"];
    EighthSTATE -> NinthSTATE;
    TenthSTATE [label="Tenth State" URL="\ref TenthSTATE"];
    EleventhSTATE [label="Eleventh State?" shape="diamond"];
    EleventhSTATE -> ERROR [label="Yes" ];
    EleventhSTATE -> TwelfthSTATE [label="No" ];
    TenthSTATE -> EleventhSTATE;
    TwelfthSTATE [label="Twelfth State" URL="\ref TwelfthSTATE"];
}

Answer 2

每当您想要一个向上的箭头时，请从上到下（即向后）编写边缘，然后添加 dir=back (https://graphviz.org/docs/attrs/dir/) 使箭头指向向上而不是向下。

因此，不要

FourthSTATE -> ThirdSTATE [label="No"];

写：

ThirdSTATE -> FourthSTATE [dir=back, label="No"];

现在，由于所有边都从 ThirdSTATE 到 FourthSTATE，因此排名不再含糊，Graphviz 将可靠地放置 ThirdSTATE位于 FourthSTATE 之上。

这通常比使用 constraint=false 更好，因为使用 constraint=false 的边有时会被赋予非常摇摆的边（就好像它们没有参与图形布局一样？）。