From 2e9535ad09e6aa2489848f51f95452d2cbfd5884 Mon Sep 17 00:00:00 2001
From: Travis Scrimshaw <tscrimsh at umn.edu>
Date: Thu, 21 Jan 2016 11:19:14 -0600
Subject: [PATCH] Make the generators of CoxeterGroup dense.

The one() element is dense because the matrix_space() is
dense. By making the generators dense, it means the generators
are not converted to dense matrices upon multiplication,
resulting in a 2x speedup to iteration.
---
 src/sage/groups/matrix_gps/coxeter_group.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/sage/groups/matrix_gps/coxeter_group.py b/src/sage/groups/matrix_gps/coxeter_group.py
index f9a68e9983b..037e19a8223 100644
--- a/src/sage/groups/matrix_gps/coxeter_group.py
+++ b/src/sage/groups/matrix_gps/coxeter_group.py
@@ -266,6 +266,8 @@ def __init__(self, coxeter_matrix, base_ring, index_set):
                                            for j in range(n)},
                               coerce=True, copy=True)
                 for i in range(n)]
+        # Make the generators dense matrices for consistancy and speed
+        gens = [g.dense_matrix() for g in gens]
         category = CoxeterGroups()
         # Now we shall see if the group is finite, and, if so, refine
         # the category to ``category.Finite()``. Otherwise the group is