chap3.txt

  
  3 Examples
  
  
  3.1 Generators
  
    Example  
    gap> C := NmzCone(["integral_closure",[[2,1],[1,3]]]);
    <a Normaliz cone>
    gap> NmzHasConeProperty(C,"HilbertBasis");
    false
    gap> NmzHasConeProperty(C,"SupportHyperplanes");
    false
    gap> NmzConeProperty(C,"HilbertBasis");
    [ [ 1, 1 ], [ 1, 2 ], [ 1, 3 ], [ 2, 1 ] ]
    gap> NmzHasConeProperty(C,"SupportHyperplanes");
    true
    gap> NmzConeProperty(C,"SupportHyperplanes");
    [ [ -1, 2 ], [ 3, -1 ] ]
  
  
  
  3.2 System of equations
  
    Example  
    gap> D := NmzCone(["equations",[[1,2,-3]], "grading",[[0,-1,3]]]);
    <a Normaliz cone>
    gap> NmzCompute(D,["DualMode","HilbertSeries"]);
    true
    gap> NmzHilbertBasis(D);
    [ [ 1, 1, 1 ], [ 0, 3, 2 ], [ 3, 0, 1 ] ]
    gap> NmzHilbertSeries(D);
    [ t^2-t+1, [ [ 1, 1 ], [ 3, 1 ] ] ]
    gap> NmzHasConeProperty(D,"SupportHyperplanes");
    true
    gap> NmzSupportHyperplanes(D);
    [ [ 1, 0, 0 ], [ 1, 3, -3 ] ]
    gap> NmzEquations(D);
    [ [ 1, 2, -3 ] ]
  
  
  
  3.3 System of inhomogeneous equations
  
    Example  
    gap> P := NmzCone(["inhom_equations",[[1,2,-3,1]], "grading", [[1,1,1]]]);
    <a Normaliz cone>
    gap> NmzIsInhomogeneous(C);
    false
    gap> NmzIsInhomogeneous(P);
    true
    gap> NmzHilbertBasis(P);
    [ [ 1, 1, 1, 0 ], [ 3, 0, 1, 0 ], [ 0, 3, 2, 0 ] ]
    gap> NmzModuleGenerators(P);
    [ [ 0, 1, 1, 1 ], [ 2, 0, 1, 1 ] ]
  
  
  
  3.4 Combined input
  
  Normaliz  also  allows  the  combination  of  different kinds of input, e.g.
  multiple constraint types, or additional data like a grading.
  
  Suppose  that you have a 3 by 3 square of nonnegative integers such that the
  3  numbers  in  all  rows,  all  columns, and both diagonals sum to the same
  constant  M.  Sometimes  such  squares  are  called magic and M is the magic
  constant.  This leads to a linear system of equations. The magic constant is
  a natural choice for the grading. Additionally we force here the 4 corner to
  have even value by adding congruences.
  
    Example  
    gap> Magic3x3even := NmzCone(["equations",
    > [ [1, 1, 1,  -1, -1, -1,   0,  0,  0],
    >   [1, 1, 1,   0,  0,  0,  -1, -1, -1],
    >   [0, 1, 1,  -1,  0,  0,  -1,  0,  0],
    >   [1, 0, 1,   0, -1,  0,   0, -1,  0],
    >   [1, 1, 0,   0,  0, -1,   0,  0, -1],
    >   [0, 1, 1,   0, -1,  0,   0,  0, -1],
    >   [1, 1, 0,   0, -1,  0,  -1,  0,  0] ],
    > "congruences",
    > [ [1, 0, 0,   0, 0, 0,   0, 0, 0,  2],
    >   [0, 0, 1,   0, 0, 0,   0, 0, 0,  2],
    >   [0, 0, 0,   0, 0, 0,   1, 0, 0,  2],
    >   [0, 0, 0,   0, 0, 0,   0, 0, 1,  2] ],
    > "grading",
    > [ [1, 1, 1,   0, 0, 0,   0, 0, 0] ] ] );
    <a Normaliz cone>
    gap> NmzHilbertBasis(Magic3x3even);
    [ [ 0, 4, 2, 4, 2, 0, 2, 0, 4 ], [ 2, 0, 4, 4, 2, 0, 0, 4, 2 ],
      [ 2, 2, 2, 2, 2, 2, 2, 2, 2 ], [ 2, 4, 0, 0, 2, 4, 4, 0, 2 ],
      [ 4, 0, 2, 0, 2, 4, 2, 4, 0 ], [ 2, 3, 4, 5, 3, 1, 2, 3, 4 ],
      [ 2, 5, 2, 3, 3, 3, 4, 1, 4 ], [ 4, 1, 4, 3, 3, 3, 2, 5, 2 ],
      [ 4, 3, 2, 1, 3, 5, 4, 3, 2 ] ]
    gap> NmzHilbertSeries(Magic3x3even);
    [ t^3+3*t^2-t+1, [ [ 1, 1 ], [ 2, 2 ] ] ]
    gap> NmzHilbertQuasiPolynomial(Magic3x3even);
    [ 1/2*t^2+t+1, 1/2*t^2-1/2 ]
  
  
  
  3.5 Using the dual mode
  
  For  solving systems of equations and inequalities it is often faster to use
  the  dual  Normaliz  algorithm.  We  demonstrate  how  to  use  it  with  an
  inhomogeneous system of equations and inequalities.
  
  The  input  consists  of  a  system of 8 inhomogeneous equations in R^3. The
  first  row  of  the  matrix  M  encodes the inequality 8x + 8y + 8z + 7 ≥ 0.
  Additionally  we  say that x, y, z should be non-negative by giving the sign
  vector and use the total degree.
  
    Example  
    gap> M := [
    >  [ 8,  8,  8,  7 ],
    >  [ 0,  4,  0,  1 ],
    >  [ 0,  1,  0,  7 ],
    >  [ 0, -2,  0,  7 ],
    >  [ 0, -2,  0,  1 ],
    >  [ 8, 48,  8, 17 ],
    >  [ 1,  6,  1, 34 ],
    >  [ 2,-12, -2, 37 ],
    >  [ 4,-24, -4, 14 ]
    > ];
    [ [ 8, 8, 8, 7 ], [ 0, 4, 0, 1 ], [ 0, 1, 0, 7 ], [ 0, -2, 0, 7 ],
      [ 0, -2, 0, 1 ], [ 8, 48, 8, 17 ], [ 1, 6, 1, 34 ],
      [ 2, -12, -2, 37 ], [ 4, -24, -4, 14 ] ]
    gap> D := NmzCone(["inhom_inequalities", M,
    >               "signs", [[1,1,1]],
    >               "grading", [[1,1,1]]]);
    <a Normaliz cone>
    gap> NmzCompute(D,["DualMode","HilbertBasis","ModuleGenerators"]);
    true
    gap> NmzHilbertBasis(D);
    [ [ 1, 0, 0, 0 ], [ 1, 0, 1, 0 ] ]
    gap> NmzModuleGenerators(D);
    [ [ 0, 0, 0, 1 ], [ 0, 0, 1, 1 ], [ 0, 0, 2, 1 ], [ 0, 0, 3, 1 ] ]
  
  
  As  result  we  get  the  Hilbert  basis of the cone of the solutions to the
  homogeneous system and the module generators which are the base solutions to
  the inhomogeneous system.