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D.13.2.5 secondaryPolytope
Procedure from library polymake.lib (see polymake_lib).
- Usage:
- secondaryPolytope(polygon[,#]); list polygon, list #
- Assume:
- - polygon is a list of integer vectors of the same size representing
the affine coordinates of lattice points
- if the triangulations of the corresponding polygon have already been
computed with the procedure triangulations then these can be given as
a second (optional) argument in order to avoid doing this computation
again
- Purpose:
- the procedure considers the marked polytope given as the convex hull of
the lattice points and with these lattice points as markings; it then
computes the lattice points of the secondary polytope given by this
marked polytope which correspond to the triangulations computed by
the procedure triangulations
- Return:
- list, say L, such that:
L[1] = intmat, each row gives the affine coordinates of a lattice
point in the secondary polytope given by the marked
polytope corresponding to polygon
L[2] = the list of corresponding triangulations
- Note:
- if the triangluations are not handed over as optional argument the
procedure calls for its computation of these triangulations the program
points2triangs from the program topcom by Joerg Rambau, Universitaet
Bayreuth; it therefore is necessary that this program is installed in
order to use this procedure; see
http://www.rambau.wm.uni-bayreuth.de/TOPCOM/);
Example:
| LIB "polymake.lib";
==> Welcome to polymake version
==> Copyright (c) 1997-2015
==> Ewgenij Gawrilow, Michael Joswig (TU Darmstadt)
==> http://www.polymake.org
// the lattice points of the unit square in the plane
list polygon=intvec(0,0),intvec(0,1),intvec(1,0),intvec(1,1);
// the secondary polytope of this lattice point configuration is computed
list secpoly=secondaryPolytope(polygon);
==> Evaluating Commandline Options ...
==> ... done.
==> 0
==> 0
// the points in the secondary polytope
print(secpoly[1]);
==> 1 2 2 1
==> 2 1 1 2
// the corresponding triangulations
secpoly[2];
==> [1]:
==> [1]:
==> 1,2,3
==> [2]:
==> 2,3,4
==> [2]:
==> [1]:
==> 1,3,4
==> [2]:
==> 1,2,4
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