qvoronoi strangeness

out.dat

30
5 1 10 0 2 1
5 1 4 0 2 1
5 3 12 0 3 1
5 3 4 0 3 1
5 4 7 0 3 4
5 4 5 0 2 4
6 4 13 1 2 4 3
5 5 14 0 4 2
5 7 16 3 4 0
5 9 12 0 6 1
5 9 10 0 1 6
5 10 19 0 6 8
5 10 11 0 2 8
6 10 13 1 2 8 6
5 11 14 0 8 2
5 12 21 0 6 5
5 12 15 0 3 5
6 12 13 1 3 5 6
6 13 14 2 4 7 8
6 13 16 3 5 7 4
6 13 22 6 5 7 8
5 14 23 0 8 7
5 14 17 0 7 4
5 15 16 3 5 0
5 16 25 0 5 7
5 16 17 4 0 7
5 19 22 6 8 0
5 21 22 6 5 0
5 22 25 5 0 7
5 22 23 7 0 8

pts.dat

3
27
0 2 0
1 2 0
2 2 0
0 1 0
1 1 0
2 1 0
0 0 0
1 0 0
2 0 0
0 2 1
1 2 1
2 2 1
0 1 1
1 1 1
2 1 1
0 0 1
1 0 1
2 0 1
0 2 2
1 2 2
2 2 2
0 1 2
1 1 2
2 1 2
0 0 2
1 0 2
2 0 2

python_output.txt

ridges: set([(25, 16), (22, 13), (23, 22), (14, 13), (22, 19), (17, 16), (25, 22), (12, 9), (16, 7), (15, 12), (11, 10), (14, 5), (16, 15), (21, 12), (4, 1), (13, 4), (10, 9), (5, 4), (13, 12), (23, 14), (10, 1), (13, 10), (19, 10), (14, 11), (22, 21), (17, 14), (7, 4), (12, 3), (4, 3), (16, 13)])
python equals qhull: True

run.sh

qvoronoi p Fv < pts.dat > out.dat

same_in_python.py

#!/usr/bin/env python
import numpy as np
from scipy.spatial import Voronoi

points = np.loadtxt('pts.dat', skiprows=2)
vor = Voronoi(points)

# Compare to qhull
def makepair(a, b):
    if a > b:
        a, b = b, a
    return (int(b), int(a))

py_ridges = set(makepair(x[0], x[1]) for x in vor.ridge_points)

qhull_dat = np.loadtxt('out.dat', skiprows=1)
qhull_ridges = set(makepair(row[1], row[2]) for row in qhull_dat)

print "ridges:", py_ridges
print "python equals qhull:", py_ridges == qhull_ridges