Cannot compute integral points of 0-dimensional Polyhedron

[jdemeyer]

A trivial case, but it should work anyway:

sage: P = Polyhedron([[]])
sage: P
A 0-dimensional polyhedron in ZZ^0 defined as the convex hull of 1 vertex
sage: P.integral_points()
---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-13-2abbf2adff15> in <module>()
----> 1 P.integral_points()

/usr/local/src/sage-git/local/lib/python2.7/site-packages/sage/geometry/polyhedron/base.pyc in integral_points(self, threshold)
   3826                 box_points<threshold:
   3827             from sage.geometry.integral_points import rectangular_box_points
-> 3828             return rectangular_box_points(box_min, box_max, self)
   3829 
   3830         # for more complicate polytopes, triangulate & use smith normal form

/usr/local/src/sage-git/src/sage/geometry/integral_points.pyx in sage.geometry.integral_points.rectangular_box_points (build/cythonized/sage/geometry/integral_points.c:4761)()
    531     v = vector(ZZ, d)
    532     if not return_saturated:
--> 533         for p in loop_over_rectangular_box_points(box_min, box_max, inequalities, d, count_only):
    534             #  v = vector(ZZ, orig_perm.action(p))   # too slow
    535             for i in range(0,d):

/usr/local/src/sage-git/src/sage/geometry/integral_points.pyx in sage.geometry.integral_points.loop_over_rectangular_box_points (build/cythonized/sage/geometry/integral_points.c:5605)()
    580     while True:
    581         inequalities.prepare_inner_loop(p)
--> 582         i_min = box_min[0]
    583         i_max = box_max[0]
    584         # Find the lower bound for the allowed region

IndexError: list index out of range

CC: @nathanncohen

Component: geometry

Author: Jeroen Demeyer

Branch/Commit: eb6ba85

Reviewer: Nathann Cohen

Issue created by migration from https://trac.sagemath.org/ticket/17937

[jdemeyer]

Branch: u/jdemeyer/cannot_compute_integral_points_of_0_dimensional_polyhedron

[jdemeyer]

New commits:

eb6ba85

Fix integral_points() for polyhedra in 0 dimensions

[jdemeyer]

Author: Jeroen Demeyer

[jdemeyer]

Commit: eb6ba85

[nathanncohen]

Reviewer: Nathann Cohen

[nathanncohen]

comment:4

Looks good. I pondered a bit over the "single point in zero dimension", but well. Sounds like a valid convention.

Thanks,

Nathann

[jdemeyer]

comment:5

Replying to @nathanncohen:

Looks good. I pondered a bit over the "single point in zero dimension", but well. Sounds like a valid convention.

The zero dimensional vector space consists of one element: the zero element. There are two polytopes in this space: the empty polytope and the polytope with one vertex, namely the zero element.

[vbraun]

Changed branch from u/jdemeyer/cannot_compute_integral_points_of_0_dimensional_polyhedron to eb6ba85