# Optimizing dot files by removing redundant information

**URL:** <https://forum.graphviz.org/t/optimizing-dot-files-by-removing-redundant-information/603>\
**Category:** Uncategorized\
**Created:** [April 11, 2021, 6:40pm UTC](https://forum.graphviz.org/t/optimizing-dot-files-by-removing-redundant-information/603 "2021-04-11T18:40:50Z")\
**Posts on this page:** 10\
**Page:** 1

<div class="post-metadata">

**Author:** ![t-b](https://avatars.discourse-cdn.com/v4/letter/t/85e7bf/32.png) [@t-b](https://forum.graphviz.org/u/t-b)\
**Post date:** [April 11, 2021, 6:40pm UTC](https://forum.graphviz.org/t/optimizing-dot-files-by-removing-redundant-information/603/1 "2021-04-11T18:40:50Z")

</div>

I’m using dot graphs for communicating and documenting complex programming logic to non-programmers and my future self.

After a longish search I finally found a usable interactive dot editor, namely (don’t laugh, this really is the best ❤) dotty.

The output of dotty is quite chatty, but today I found that the `canon` output format strips away any redundant information. ✨

But dotty has the habit to create random node names instead of using the label as node name.

So even after optimization using canon I end up with something like

```auto
digraph g {
...
        n0 [label=A];
        n1 [label=B];
        n0 -> n1;
}

```

where I actually would prefer

```auto
digraph g {

A;
B;
A -> B;
}

```

Is there a tool around which can do that?

---

<div class="post-metadata">

**Author:** ![magjac](https://sea2.discourse-cdn.com/graphviz/user_avatar/forum.graphviz.org/magjac/32/16_2.png) [@magjac](https://forum.graphviz.org/u/magjac)\
**Post date:** [April 11, 2021, 7:24pm UTC](https://forum.graphviz.org/t/optimizing-dot-files-by-removing-redundant-information/603/2 "2021-04-11T19:24:15Z")

</div>

Shamless plug: the [Graphviz Visual Editor](http://magjac.com/graphviz-visual-editor/). It currently cannot do what you ask since it also inserts nodes named n_X_ where _X_ is just a serial number, but if you have a suggestion for how an interface should work that would allow you to do what you want, I might implement it.

I can think of two ways to achieve this:

1. Let the user select different schemes for automatically naming inserted nodes, where one could be A, B, …, Z and continue with AA, BB, … or A1, B1, C1, …
2. Let the user enter the node name before inserting it.

---

<div class="post-metadata">

**Author:** ![t-b](https://avatars.discourse-cdn.com/v4/letter/t/85e7bf/32.png) [@t-b](https://forum.graphviz.org/u/t-b)\
**Post date:** [April 11, 2021, 8:42pm UTC](https://forum.graphviz.org/t/optimizing-dot-files-by-removing-redundant-information/603/3 "2021-04-11T20:42:32Z")

</div>

Thanks for the link. This looks nice, and while playing around works pretty good as well.

My idea regarding node labelling would be to replace the node name, e.g. n1, with its label once a label different from `\N` is set for that node.

---

<div class="post-metadata">

**Author:** ![magjac](https://sea2.discourse-cdn.com/graphviz/user_avatar/forum.graphviz.org/magjac/32/16_2.png) [@magjac](https://forum.graphviz.org/u/magjac)\
**Post date:** [April 11, 2021, 11:02pm UTC](https://forum.graphviz.org/t/optimizing-dot-files-by-removing-redundant-information/603/4 "2021-04-11T23:02:24Z")

</div>

1. Not all labels are valid node IDs. E.g. spaces are not allowed.
2. The only way to add a label today is to write it in the DOT source. Are you suggesting that the editor should detect that and change the node ID accordingly?

---

<div class="post-metadata">

**Author:** ![t-b](https://avatars.discourse-cdn.com/v4/letter/t/85e7bf/32.png) [@t-b](https://forum.graphviz.org/u/t-b)\
**Post date:** [April 12, 2021, 12:17pm UTC](https://forum.graphviz.org/t/optimizing-dot-files-by-removing-redundant-information/603/5 "2021-04-12T12:17:14Z")

</div>

> Not all labels are valid node IDs. E.g. spaces are not allowed.

You can enclose it in double quotes

```dot
digraph g {

"Hi there!";
"Good morning";
"Hi there!" -> "Good morning";
}

```

> The only way to add a label today is to write it in the DOT source. Are you suggesting that the editor should detect that and change the node ID accordingly?

That could be one way.

---

<div class="post-metadata">

**Author:** ![steveroush](https://avatars.discourse-cdn.com/v4/letter/s/a9adbd/32.png) [@steveroush](https://forum.graphviz.org/u/steveroush)\
**Post date:** [April 12, 2021, 2:33pm UTC](https://forum.graphviz.org/t/optimizing-dot-files-by-removing-redundant-information/603/6 "2021-04-12T14:33:55Z")

</div>

Do your graphs contain sub-graphs? Do they contain more than 1 left-brace and 1 right-brace {}

---

<div class="post-metadata">

**Author:** ![t-b](https://avatars.discourse-cdn.com/v4/letter/t/85e7bf/32.png) [@t-b](https://forum.graphviz.org/u/t-b)\
**Post date:** [April 14, 2021, 1:26pm UTC](https://forum.graphviz.org/t/optimizing-dot-files-by-removing-redundant-information/603/7 "2021-04-14T13:26:16Z")

</div>

@steveroush No just one graph. dotty had problems with subgraphs.

---

<div class="post-metadata">

**Author:** ![t-b](https://avatars.discourse-cdn.com/v4/letter/t/85e7bf/32.png) [@t-b](https://forum.graphviz.org/u/t-b)\
**Post date:** [April 14, 2021, 1:31pm UTC](https://forum.graphviz.org/t/optimizing-dot-files-by-removing-redundant-information/603/8 "2021-04-14T13:31:47Z")

</div>

If there is no ready made tool, I guess I don’t need to reinvent the wheel start writing a parser for dot files, or? Any good APIs/packages (C/C++/Python/perl) I could leverage?

---

<div class="post-metadata">

**Author:** ![steveroush](https://avatars.discourse-cdn.com/v4/letter/s/a9adbd/32.png) [@steveroush](https://forum.graphviz.org/u/steveroush)\
**Post date:** [April 14, 2021, 3:53pm UTC](https://forum.graphviz.org/t/optimizing-dot-files-by-removing-redundant-information/603/9 "2021-04-14T15:53:30Z")

</div>

This **GVPR** program is lightly tested. It is not a general-purpose solution (it drops all subgraphs), but seemingly does what you want.  
Command line:  
`gvpr -f simpleRename.gvpr myfile.gv`  
Here is simpleRename.gvpr:

```
/*
  Generate copy of input graph, replacing names with labels
  NOTE: DOES NOT COPY SUBGRAPHS!
  NOTE: ugly if you use record OR html nodes
*/
BEGIN {
int id = 0;
int cnt[];
string names[string];

string mapn (string inname, string lbl){
   string s;

   s = names[inname];
   if (lbl==""){
     print("// Error:: node ", inname, " has no label");
     s=inname;
   }if (cnt[lbl]>0){
     print("// Error:: duplicate label >", lbl, "<");
     s=inname;
   }else{
     if (s == "") {
       s = lbl;
       cnt[lbl]=1;
      }
   }
   names[inname] = s;
   //print("// mapn returning: ", s);
   return s;
}

string getmapn (string inname){
   string s;

   s = names[inname];
   if (s == "") {
     print("// Error:: Edge had mapping problem with: ", inname);
   }
   names[inname] = s;
   return s;
}

}

BEG_G {
  graph_t g;
  node_t aNode;
  
  g=copy (NULL, $G);
  for (aNode=fstnode($G);aNode;aNode = nxtnode(aNode)){
    node (g, mapn(aNode.name, aNode.label));
  }
}
E { edge (node (g, getmapn($.tail.name)), node (g, getmapn($.head.name)), ""); }
END_G {
  write (g);
}
```

---

<div class="post-metadata">

**Author:** ![t-b](https://avatars.discourse-cdn.com/v4/letter/t/85e7bf/32.png) [@t-b](https://forum.graphviz.org/u/t-b)\
**Post date:** [June 7, 2021, 1:46pm UTC](https://forum.graphviz.org/t/optimizing-dot-files-by-removing-redundant-information/603/10 "2021-06-07T13:46:12Z")

</div>

Thanks @steveroush , that is great start. I knew my dormant AWK skills are there for something.

I’m attaching a refined version of your script. It handles \N as labels for nodes and also keeps edge labels.

```auto
/* vim: set ft=awk:
 *
 * Generate copy of input graph, replacing names with labels
 * NOTE: DOES NOT COPY SUBGRAPHS!
 * NOTE: ugly if you use record OR html nodes
*/

BEGIN {
  int id = 0;
  int cnt[];
  string names[string];

  string mapn (string inname, string lbl)
  {
     string s;

     s = names[inname];

     /* print("// mapn returning: >", s, "< with inname >", inname, "< and lbl >", lbl, "<"); */

     if(!strcmp(lbl,""))
     {
       print("// Error:: node ", inname, " has no label");
       s = inname;
     }
     else
     {
       if(!strcmp(lbl,"\\N"))
       {
         lbl = inname;
       }
     }

     if(cnt[lbl] > 0)
     {
       print("// Error:: duplicate label >", lbl, "<");
       s = inname;
     }
     else
     {
       if(!strcmp(s, ""))
       {
         s = lbl;
         cnt[lbl] = 1;
       }
     }

     names[inname] = s;

     return s;
  }

  string getmapn (string inname)
  {
     string s;

     s = names[inname];
     if (s == "") {
       print("// Error:: Edge had mapping problem with: ", inname);
     }

     return s;
  }
}

BEG_G {
  graph_t g;
  node_t aNode;

  g = copy (NULL, $G);
  for (aNode = fstnode($G);aNode;aNode = nxtnode(aNode)){
    node (g, mapn(aNode.name, aNode.label));
  }
}

E {
  edge_t e = edge (node (g, getmapn($.tail.name)), node (g, getmapn($.head.name)), "");
  e.label = $.label;
}

END_G {
  write (g);
}

```

My test input

```auto
digraph g {
        n0 [label=A];
        n1 [label=B];
        C [label="\N"];
        n0 -> n1 [label = "Yes"];
        n1 -> C [label = "No"];
}

```