[PPL-devel] integer versus rational solutions

[Tobias Grosser]

Hi,

I just tried to use the ppl to work with integer polyhedron, however I
am stuck with the examples in the documentation for the
Partial_Reduced_Product:

http://www.cs.unipr.it/ppl/Documentation/user/ppl-user-0.10.2-html/classParma__Polyhedra__Library_1_1Partially__Reduced__Product.html#_details

---------------------------------------------------------------------
In all the examples it is assumed that the template R is the
No_Reduction<D1, D2> class and that variables x and y are defined (where
they are used) as follows: 
          Variable x(0);
          Variable y(1);
        
Example 1
        The following code builds a direct product of a Grid and NNC
        Polyhedron, corresponding to the positive even integer pairs in
        R^2, given as a system of congruences: 
        
          Congruence_System cgs;
          cgs.insert((x %= 0) / 2);
          cgs.insert((y %= 0) / 2);
          Partially_Reduced_Product<Grid, NNC_Polyhedron, No_Reduction<D1, D2> >
            dp(cgs);
          dp.add_constraint(x >= 0);
          dp.add_constraint(y >= 0);
        
Example 2
        The following code builds the same product in R^2: 
        Partially_Reduced_Product<Grid, NNC_Polyhedron, No_Reduction<D1, D2> > dp(2);
          dp.add_constraint(x >= 0);
          dp.add_constraint(y >= 0);
          dp.add_congruence((x %= 0) / 2);
          dp.add_congruence((y %= 0) / 2);
---------------------------------------------------------------------

I would like to create the set of even positive integer pairs, so I
tried Example 1 and 2. With both I have the same problems.

1. D1 and D2 are not defined:

test.cpp:9: error: 'D1' was not declared in this scope
test.cpp:9: error: 'D2' was not declared in this scope

So I replace D1 with "Grid" and D2 with "NNC_Polyhedron"

2. An exception when adding constrains:

terminate called after throwing an instance of 'std::invalid_argument'
  what():  PPL::Grid::add_constraint(c):
c is not an equality constraint.

So I removed the positive constraints.

3. An exception when adding congruences:

terminate called after throwing an instance of 'std::invalid_argument'
  what():  PPL::NNC_Polyhedron::add_congruence(cg):
cg is a non-trivial, proper congruence.

Do you have any idea what I did wrong?

Tobias