Re: Extracting a reachability path out of a (package) DAG

[ludo@gnu.org (Ludovic Courtès)]

Hi Björn,

Björn Höfling <bjoern.hoefling@bjoernhoefling.de> skribis:

> To answer this, I want to extract from hello's package graph the path
> (more precisely: the sub-DAG) leading from the root "hello" to the
> target node (or even nodes) "goodbye".
>
> After several attempts and failures, I wrote a script for gvpr from
> the GraphViz suite that does the job.
>
> Example 1: In bug #30710 Hartmut Goebel asked why qt depends on two
> different autoconf-wrapper packages. To answer that, you can find out
> the two node names from the .dot file and then call:
>
> gvpr -f markpath.g -a "ex 64168128 64167936" < qt-thing/qt.package.dot
>>qt-acw.dot
>
> This extracts (ex) the path (sub-DAG) to the two seed nodes and outputs
> it in a new graph. This result is quite compact with only 12 nodes (attached).

That’s excellent!  I didn’t know about gvpr and its scripting
capabilities, really nice (GraphViz also has Guile bindings, not sure if
they would help here?).

It may be nice to have some of this functionality available directly in
(guix graph) because these are very common questions one may ask.
Future work!

Thanks,
Ludo’.