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authorRelease Manager <release@sagemath.org>2015-08-05 12:52:30 +0200
committerVolker Braun <vbraun.name@gmail.com>2015-08-05 12:52:30 +0200
commit64625bc72b399440f4cc2a98ec0c0f05a292d65a (patch)
treec5abce8e782588f97be846ca484da53f2afc6eee
parentTrac #18960: Strongly Regular Graphs from two-weight codes (diff)
parenttrac #18988: Merged with updated #18960 (diff)
Trac #18988: Orthogonal Polar graphs in strongly_regular_graph
As reported by Dima in #18948, a family was missing from the general constructor. This branch adds it. Nathann URL: http://trac.sagemath.org/18988 Reported by: ncohen Ticket author(s): Nathann Cohen Reviewer(s): Dima Pasechnik
-rw-r--r--src/sage/graphs/strongly_regular_db.pyx81
1 files changed, 79 insertions, 2 deletions
diff --git a/src/sage/graphs/strongly_regular_db.pyx b/src/sage/graphs/strongly_regular_db.pyx
index 19620b0..6a7d789 100644
--- a/src/sage/graphs/strongly_regular_db.pyx
+++ b/src/sage/graphs/strongly_regular_db.pyx
@@ -252,6 +252,82 @@ def is_affine_polar(int v,int k,int l,int mu):
from sage.graphs.generators.families import AffineOrthogonalPolarGraph
return (lambda d,q : AffineOrthogonalPolarGraph(d,q,sign='-'),2*e,q)
+@cached_function
+def is_orthogonal_polar(int v,int k,int l,int mu):
+ r"""
+ Test whether some Orthogonal Polar graph is `(v,k,\lambda,\mu)`-strongly regular.
+
+ For more information, see http://www.win.tue.nl/~aeb/graphs/srghub.html.
+
+ INPUT:
+
+ - ``v,k,l,mu`` (integers)
+
+ OUTPUT:
+
+ A tuple ``t`` such that ``t[0](*t[1:])`` builds the requested graph if one
+ exists, and ``None`` otherwise.
+
+ EXAMPLES::
+
+ sage: from sage.graphs.strongly_regular_db import is_orthogonal_polar
+ sage: t = is_orthogonal_polar(85, 20, 3, 5); t
+ (<function OrthogonalPolarGraph at ...>, 5, 4, '')
+ sage: g = t[0](*t[1:]); g<