Working With Polyhedron Representations

class cdd.Polyhedron(mat)

A class for converting between representations of a polyhedron.

Bases: NumberTypeable

Parameters:mat (Matrix) – The matrix to load the polyhedron from.

Methods and Attributes

Polyhedron.get_inequalities()

Get all inequalities.

Returns:H-representation. Return type:Matrix

Polyhedron.get_generators()

Get all generators.

Returns:V-representation. Return type:Matrix

Polyhedron.rep_type

Representation (see RepType).

Note

The H-representation and/or V-representation are not guaranteed to be minimal, that is, they can still contain redundancy.

Example

This is the sampleh1.ine example that comes with cddlib.

>>> import cdd
>>> mat = cdd.Matrix([[2,-1,-1,0],[0,1,0,0],[0,0,1,0]], number_type='fraction')
>>> mat.rep_type = cdd.RepType.INEQUALITY
>>> poly = cdd.Polyhedron(mat)
>>> print(poly)
begin
 3 4 rational
 2 -1 -1 0
 0 1 0 0
 0 0 1 0
end
>>> ext = poly.get_generators()
>>> print(ext)
V-representation
linearity 1  4
begin
 4 4 rational
 1 0 0 0
 1 2 0 0
 1 0 2 0
 0 0 0 1
end
>>> print(list(ext.lin_set)) # note: first row is 0, so fourth row is 3
[3]