New subject: Query on checking out the 'devel' branch

6 Mar 2022


      Hello,
For a project I am working on with a collaborator, I have the extreme
points and the rays of a polyhedron. I have to obtain the
facetious representation of this polyhedron. That is, I want a simple V to
H conversion.
I have been working with polymake so far. My working code is:
#include <polymake/Main.h>
#include <polymake/Matrix.h>
#include <polymake/SparseMatrix.h>
#include <polymake/Rational.h>
using namespace polymake;
int main(int argc, const char* argv[]) {
  try {
    Main pm;
    pm.set_application("polytope");
    BigObject p("Polytope<Rational>");
    std::vectorstd::string CoordinateLabels = { "extravar", "x1", "x2",
"x3", "x4", "x5", "x6"};
    std::vector<std::vector<Int>> Points;
    std::vector<Int> point;
    point = { 1,0,1,1,0,0,1 }; Points.push_back(point);
    point = { 1,1,0,0,1,1,0 }; Points.push_back(point);
    point = { 1,0,0,1,1,0,1 }; Points.push_back(point);
    point = { 1,1,0,0,1,1,0 }; Points.push_back(point);
    point = { 1,0,1,1,0,0,1 }; Points.push_back(point);
    point = { 1,1,0,0,1,1,0 }; Points.push_back(point);
    point = { 1,0,1,1,0,0,1 }; Points.push_back(point);
    point = { 1,0,0,0,1,1,1 }; Points.push_back(point);
    point = { 0,1,0,0,0,0,0 }; Points.push_back(point);
    point = { 0,0,1,0,0,0,0 }; Points.push_back(point);
    point = { 0,0,0,1,0,0,0 }; Points.push_back(point);
    point = { 0,0,0,0,1,0,0 }; Points.push_back(point);
    point = { 0,0,0,0,0,1,0 }; Points.push_back(point);
    point = { 0,0,0,0,0,0,1 }; Points.push_back(point);
    p.take("VERTICES") << Points;
    const Matrix<Rational> f = p.give("FACETS");
    cout << "facets" << endl << f << endl;
    cout << "Dimension of the facets matrix are " << f.rows() << " and " <<
f.cols() << endl;
    cout << "Printing the facets for easy reading" << endl;
    for (int i = 0; i < f.rows(); i++) {
      cout << " Facet " << i << ": ";
      Rational rhs = f(i, 0);
      for (int j = 1; j < f.cols(); j++) {
        Rational coef = f(i, j);
        if (coef.is_zero() == false) {
          cout << " + (" << coef << " " << CoordinateLabels[j] << ") ";
        }
      }
      cout << " >= - (" << rhs << ")" << endl;
    }
    const Matrix<Rational> affine_hull = p.give("AFFINE_HULL");
    cout << "affine hull" << endl << affine_hull << endl;
    cout << "Dimension of the affine hull matrix are " <<
affine_hull.rows() << " and " << affine_hull.cols() << endl;
    cout << "Printing the affine hull for easy reading" << endl;
    for (int i = 0; i < affine_hull.rows(); i++) {
      printf("AffineHull %d: ", i);
      Rational rhs = affine_hull(i, 0);
      for (int j = 1; j < affine_hull.cols(); j++) {
        Rational coef = affine_hull(i, j);
        if (coef.is_zero() == false) {
          cout << " + (" << coef << " " << CoordinateLabels[j] << ") ";
        }
      }
      cout << " = - (" << rhs << ")" << endl;
    }
  }
  catch (const std::exception& ex) {
    std::cerr << "ERROR: " << ex.what() << endl; return 1;
  }
  return 0;
}
The code can also be seen on godbolt at : https://godbolt.org/z/Ko7zq4z64
The output of the above program is:
polymake: used package ppl
  The Parma Polyhedra Library ([[wiki:external_software#PPL]]): A C++
library for convex polyhedra
  and other numerical abstractions.
  http://www.cs.unipr.it/ppl/
facets
-1 0 0 1 0 1 0
0 0 0 1 0 0 0
0 0 1 0 0 0 0
-1 0 1 0 1 0 0
-1 0 0 1 1 0 0
0 0 0 0 1 0 0
0 0 0 0 0 1 0
0 1 0 0 0 0 0
-1 1 0 0 0 0 1
0 0 0 0 0 0 1
-1 0 0 0 1 0 1
-1 0 0 0 0 1 1
1 0 0 0 0 0 0
Dimension of the facets matrix are 13 and 7
Printing the facets for easy reading
 Facet 0:  + (1 x3)  + (1 x5)  >= - (-1)
 Facet 1:  + (1 x3)  >= - (0)
 Facet 2:  + (1 x2)  >= - (0)
 Facet 3:  + (1 x2)  + (1 x4)  >= - (-1)
 Facet 4:  + (1 x3)  + (1 x4)  >= - (-1)
 Facet 5:  + (1 x4)  >= - (0)
 Facet 6:  + (1 x5)  >= - (0)
 Facet 7:  + (1 x1)  >= - (0)
 Facet 8:  + (1 x1)  + (1 x6)  >= - (-1)
 Facet 9:  + (1 x6)  >= - (0)
 Facet 10:  + (1 x4)  + (1 x6)  >= - (-1)
 Facet 11:  + (1 x5)  + (1 x6)  >= - (-1)
 Facet 12:  >= - (1)
affine hull
Dimension of the affine hull matrix are 0 and 7
Printing the affine hull for easy reading
I have two queries:
(1) Is there a simple example that shows how the equivalent of the above
functionality can be obtained in PPL via C/C+ code? I have looked at the
PPL user manual, but I have to admit that it is quite forbidding in its
size and details and it is not fully clear where in the document complete
C/C++ examples are. I admit that this is possibly my lack of delving too
deep into the manual.
I also notice that Polymake has solved this problem by calling PPL behind
the scenes.
(2) Can the PPL code I write on Linux/WSL be used on a Windows Machine as
well? I ask this because this is not a possibility in Polymake. Indeed, I
was guided towards PPL as a result of my query on the Polymake forum.
Polymake code cannot run on a Windows machine. I was wondering if PPL has
this capability as suggested there. Please see that discussion at:
https://forum.polymake.org/viewtopic.php?f=8&p=3919
Thanks.
Tryer

Static linking and running on both windows and linux

anoninus

Roberto Bagnara

anoninus

Roberto Bagnara

anoninus

Roberto Bagnara

anoninus

Roberto Bagnara

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anoninus

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Roberto Bagnara

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