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/* Copyright (c) 1997-2024
Ewgenij Gawrilow, Michael Joswig, and the polymake team
Technische Universität Berlin, Germany
https://polymake.org
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version: http://www.gnu.org/licenses/gpl.txt.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
--------------------------------------------------------------------------------
*/
#pragma once
#include "polymake/client.h"
#include "polymake/Graph.h"
#include "polymake/Set.h"
#include "polymake/Array.h"
#include "polymake/vector"
#include "polymake/IncidenceMatrix.h"
#include <algorithm>
#include "polymake/graph/Decoration.h"
#include "polymake/graph/Closure.h"
namespace polymake { namespace graph { namespace lattice {
// Every CrossCut needs to provide an operator
//
// bool operator()(const Decoration& data), which accepts a decoration and then returns whether this
// node should be kept (true) or discarded (false).
/*
* The trivial cut - accepts everything
*/
template <typename Decoration>
class TrivialCut {
public:
TrivialCut() = default;
bool operator()(const Decoration& data) const { return true; }
};
/*
* Only keeps sets not intersecting a fixed set
*/
template <typename Decoration>
class SetAvoidingCut {
protected:
const Set<Int> avoid;
public:
SetAvoidingCut(const Set<Int>& set_arg) : avoid(set_arg) {}
bool operator()(const Decoration &data) const
{
return (data.face * avoid).empty();
}
};
/*
* Only keeps sets smaller than the full set.
*/
template <typename Decoration>
class NotFullSetCut {
protected:
const Int full_set_size;
public:
NotFullSetCut(const Int full_set_size_)
: full_set_size(full_set_size_) {}
bool operator()(const Decoration& data) const
{
return data.face.size() < full_set_size;
}
};
namespace RankCutType {
const bool GreaterEqual = false;
const bool LesserEqual = true;
}
/*
* Only keeps nodes whose rank is greater equal (or lesser equal) a certain number.
*/
template <typename Decoration, bool lesser_equal>
class RankCut {
protected:
const Int compare;
public:
RankCut(Int comp_arg)
: compare(comp_arg) {}
bool operator()(const Decoration& data) const
{
return lesser_equal ? data.rank <= compare : data.rank >= compare;
}
};
/*
* This encapsulates various parameters for restricting the rank of a lattice.
*/
struct RankRestriction {
Int boundary_rank; // up to which dimension (included!)
bool rank_restricted; // Do we want to restrict the rank?
bool rank_restriction_type; // RankCutType::LesserEqual or ::GreaterEqual
RankRestriction()
: boundary_rank(0)
, rank_restricted(false)
, rank_restriction_type(false) {}
RankRestriction(bool res_arg, bool res_type, Int dim_arg)
: boundary_rank(dim_arg)
, rank_restricted(res_arg)
, rank_restriction_type(res_type) {}
};
/*
* Makes a cut from two cuts: Both have to return true for a final true value
*/
template <typename C1, typename C2>
class CutAnd {
protected:
const C1& c1;
const C2& c2;
public:
CutAnd(const C1& a1, const C2& a2)
: c1(a1), c2(a2) {}
template <typename Decoration>
bool operator()(const Decoration& data) const
{
return c1(data) && c2(data);
}
};
/*
* In the lattice building algorithm, the data handled by the closure operator can be different
* from the data one wants to attach to the final lattice.
* The decorator converts the closure data to the actual decoration.
* It needs to provide the following interface:
* - const Decoration compute_initial_decoration(const ClosureData& face) const:
* Here, Decoration needs to match the Decoration of the corresponding lattice and
* ClosureData must be the ClosureData returned by the closure operator. The function computes
* the decoration of the initial node.
* - const Decoration compute_decoration(const ClosureData& face, const Decoration& predecessor_data) const:
* Given the closure data of a node and the decoration of *one of* its predecessors, this computes
* the decoration of this node.
* - const Decoration compute_artificial_decoration(const NodeMap<Directed, BasicDecoration>& decor,
* const std::list<Int>& max_nodes) const
* In some cases, an artificial top node is added to the lattice at the end of the algorithm. This
* computes its decor from a node map containing all previous decorations and a list of indices of all
* nodes which are maximal.
*/
/*
* The basic decorator: Faces are either the sets computed during the closure algorithm
* or the intersection of the corresponding coatoms (if built dually).
* Ranks are computed as heights in the lattice plus a potential shift.
*/
template <typename FaceData = BasicClosureOperator<BasicDecoration>::ClosureData>
class BasicDecorator {
protected:
const Int total_size;
const Int initial_rank;
const bool built_dually;
const Set<Int> artificial_set;
public:
// dual type
BasicDecorator(Int n_vertices, Int top_rank, const Set<Int> artificial)
: total_size(n_vertices)
, initial_rank(top_rank)
, built_dually(true)
, artificial_set(artificial) {}
//primal type
BasicDecorator(Int bottom_rank, const Set<Int> artificial)
: total_size(0)
, initial_rank(bottom_rank)
, built_dually(false)
, artificial_set(artificial) {}
BasicDecoration compute_decoration(const FaceData& face,
const BasicDecoration& predecessor_data) const
{
BasicDecoration data;
data.rank = predecessor_data.rank + (built_dually ? -1 : 1);
data.face = built_dually ? face.get_dual_face() : face.get_face();
return data;
}
BasicDecoration compute_initial_decoration(const FaceData& face) const
{
BasicDecoration data;
data.rank = initial_rank;
data.face = built_dually? face.get_dual_face() : face.get_face();
return data;
}
BasicDecoration compute_artificial_decoration(const NodeMap<Directed, BasicDecoration>& decor,
const std::list<Int>& max_nodes) const
{
BasicDecoration data;
auto max_list = attach_member_accessor( select(decor, max_nodes),
ptr2type<BasicDecoration, Int, &BasicDecoration::rank>()
);
data.rank = built_dually ?
accumulate(max_list, operations::min())-1 :
accumulate(max_list, operations::max())+1 ;
data.face = artificial_set;
return data;
}
};
} } }
// Local Variables:
// mode:C++
// c-basic-offset:3
// indent-tabs-mode:nil
// End:
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