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/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
/*
* Main authors:
* Christian Schulte <schulte@gecode.org>
*
* Copyright:
* Christian Schulte, 2004, 2016
*
* This file is part of Gecode, the generic constraint
* development environment:
* http://www.gecode.org
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
*/
#ifndef GECODE_SEARCH_SEQ_LDS_HH
#define GECODE_SEARCH_SEQ_LDS_HH
#include <gecode/search.hh>
#include <gecode/search/support.hh>
#include <gecode/search/worker.hh>
namespace Gecode { namespace Search { namespace Seq {
/// %Probe engine for %LDS
template<class Tracer>
class Probe : public Worker {
protected:
/// Node identity type
typedef typename Tracer::ID ID;
/// %Node in the search tree for %LDS
class Node {
private:
/// %Space of current node
Space* _space;
/// Choice
const Choice* _choice;
/// Next alternative to try
unsigned int _alt;
/// Node identifier
ID _nid;
public:
/// Default constructor
Node(void);
/// Initialize with node \a s, choice \a c, and alternative \a a
Node(Space* s, const Choice* c, unsigned int a, unsigned int nid);
/// Return space
Space* space(void) const;
/// Return choice
const Choice* choice(void) const;
/// Return next alternative
unsigned int alt(void) const;
/// Return node identifier
unsigned int nid(void) const;
/// %Set next alternative
void next(void);
};
/// Search tracer
Tracer tracer;
/// %Stack storing current path in search tree
Support::DynamicStack<Node,Heap> ds;
/// Current space
Space* cur;
/// Current discrepancy
unsigned int d;
/// Whether entire search space has been exhausted
bool exhausted;
public:
/// Initialize
Probe(const Options& opt);
/// Initialize with space \a s
void init(Space* s);
/// Reset with space \a s and discrepancy \a d
void reset(Space* s, unsigned int d);
/// Return statistics
Statistics statistics(void) const;
/// Destructor
~Probe(void);
/// %Search for next solution
Space* next(const Options& o);
/// Test whether probing is done
bool done(void) const;
};
/// Limited discrepancy search engine implementation
template<class Tracer>
class LDS : public Engine {
protected:
/// Search options
Options opt;
/// The probe engine
Probe<Tracer> e;
/// Root node for problem
Space* root;
/// Current discrepancy
unsigned int d;
/// Solution found for current discrepancy
bool no_solution;
public:
/// Initialize for space \a s with options \a o
LDS(Space* s, const Options& o);
/// Return next solution (nullptr, if none exists or search has been stopped)
virtual Space* next(void);
/// Return statistics
virtual Statistics statistics(void) const;
/// Constrain future solutions to be better than \a b (should never be called)
void constrain(const Space& b);
/// Reset engine to restart at space \a s
void reset(Space* s);
/// Check whether engine has been stopped
virtual bool stopped(void) const;
/// Destructor
virtual ~LDS(void);
};
}}}
#include <gecode/search/seq/lds.hpp>
#endif
// STATISTICS: search-seq
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