Add interface to nauty-gentreeg (generator of trees)

[dcoudert]

Add interface to Nauty's gentreeg generator of non-isomorphic trees.

It is slower than graphs.trees() but has more options.

Component: graph theory

Author: David Coudert

Branch: 7a5e122

Reviewer: Frédéric Chapoton

Issue created by migration from https://trac.sagemath.org/ticket/33670

[dcoudert]

Branch: public/graphs/33670_gentreeg

[dcoudert]

New commits:

077a46f

trac #33670: add interface to nauty's gentreeg

[dcoudert]

Commit: 077a46f

[fchapoton]

comment:2

typo "aggrees"

[sagetrac-git]

Changed commit from 077a46f to 7a5e122

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

7a5e122

trac #33670: fix typo

[dcoudert]

comment:4

fixed.

[fchapoton]

comment:5

feu vert

[fchapoton]

Reviewer: Frédéric Chapoton

[vbraun]

Changed branch from public/graphs/33670_gentreeg to 7a5e122

[mkoeppe]

Changed commit from 7a5e122 to none

[mkoeppe]

comment:7

I've seen a few failures related to this on CI. For example
https://github.com/mkoeppe/sage/runs/7244909758?check_suite_focus=true

sage -t --random-seed=339975412379786288587528093076040376748 src/sage/graphs/generators/families.py
**********************************************************************
File "src/sage/graphs/generators/families.py", line 3479, in sage.graphs.generators.families.nauty_gentreeg
Failed example:
    [len(list(graphs.nauty_gentreeg(str(i)))) for i in range(1, 15)]
Expected:
    [1, 1, 1, 2, 3, 6, 11, 23, 47, 106, 235, 551, 1301, 3159]
Got:
    [1, 2, 1, 2, 3, 6, 11, 23, 47, 106, 235, 551, 1301, 3159]

(that's on debian-stretch-standard using system nauty 2.6r7+ds-1)

[mkoeppe]

comment:8

I've opened #34133 for this