libs/minisat/SimpSolver.h - third_party/yosys - Git at Google

 /************************************************************************************[SimpSolver.h]
 Copyright (c) 2006,      Niklas Een, Niklas Sorensson
 Copyright (c) 2007-2010, Niklas Sorensson

 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 Minisat_SimpSolver_h
 #define Minisat_SimpSolver_h

 #include "Queue.h"
 #include "Solver.h"


 namespace Minisat {

 //=================================================================================================


 class SimpSolver : public Solver {
  public:
     // Constructor/Destructor:
     //
     SimpSolver();
     ~SimpSolver();

     // Problem specification:
     //
     Var     newVar    (lbool upol = l_Undef, bool dvar = true);
     void    releaseVar(Lit l);
     bool    addClause (const vec<Lit>& ps);
     bool    addEmptyClause();                // Add the empty clause to the solver.
     bool    addClause (Lit p);               // Add a unit clause to the solver.
     bool    addClause (Lit p, Lit q);        // Add a binary clause to the solver.
     bool    addClause (Lit p, Lit q, Lit r); // Add a ternary clause to the solver.
     bool    addClause (Lit p, Lit q, Lit r, Lit s); // Add a quaternary clause to the solver.
     bool    addClause_(      vec<Lit>& ps);
     bool    substitute(Var v, Lit x);  // Replace all occurences of v with x (may cause a contradiction).

     // Variable mode:
     //
     void    setFrozen (Var v, bool b); // If a variable is frozen it will not be eliminated.
     bool    isEliminated(Var v) const;

     // Alternative freeze interface (may replace 'setFrozen()'):
     void    freezeVar (Var v);         // Freeze one variable so it will not be eliminated.
     void    thaw      ();              // Thaw all frozen variables.


     // Solving:
     //
     bool    solve       (const vec<Lit>& assumps, bool do_simp = true, bool turn_off_simp = false);
     lbool   solveLimited(const vec<Lit>& assumps, bool do_simp = true, bool turn_off_simp = false);
     bool    solve       (                     bool do_simp = true, bool turn_off_simp = false);
     bool    solve       (Lit p       ,        bool do_simp = true, bool turn_off_simp = false);
     bool    solve       (Lit p, Lit q,        bool do_simp = true, bool turn_off_simp = false);
     bool    solve       (Lit p, Lit q, Lit r, bool do_simp = true, bool turn_off_simp = false);
     bool    eliminate   (bool turn_off_elim = false);  // Perform variable elimination based simplification.

     // Memory managment:
     //
     virtual void garbageCollect();


     // Generate a (possibly simplified) DIMACS file:
     //
 #if 0
     void    toDimacs  (const char* file, const vec<Lit>& assumps);
     void    toDimacs  (const char* file);
     void    toDimacs  (const char* file, Lit p);
     void    toDimacs  (const char* file, Lit p, Lit q);
     void    toDimacs  (const char* file, Lit p, Lit q, Lit r);
 #endif

     // Mode of operation:
     //
     int     grow;              // Allow a variable elimination step to grow by a number of clauses (default to zero).
     int     clause_lim;        // Variables are not eliminated if it produces a resolvent with a length above this limit.
                                // -1 means no limit.
     int     subsumption_lim;   // Do not check if subsumption against a clause larger than this. -1 means no limit.
     double  simp_garbage_frac; // A different limit for when to issue a GC during simplification (Also see 'garbage_frac').

     bool    use_asymm;         // Shrink clauses by asymmetric branching.
     bool    use_rcheck;        // Check if a clause is already implied. Prett costly, and subsumes subsumptions :)
     bool    use_elim;          // Perform variable elimination.
     bool    extend_model;      // Flag to indicate whether the user needs to look at the full model.

     // Statistics:
     //
     int     merges;
     int     asymm_lits;
     int     eliminated_vars;

  protected:

     // Helper structures:
     //
     struct ElimLt {
         const LMap<int>& n_occ;
         explicit ElimLt(const LMap<int>& no) : n_occ(no) {}

         // TODO: are 64-bit operations here noticably bad on 32-bit platforms? Could use a saturating
         // 32-bit implementation instead then, but this will have to do for now.
         uint64_t cost  (Var x)        const { return (uint64_t)n_occ[mkLit(x)] * (uint64_t)n_occ[~mkLit(x)]; }
         bool operator()(Var x, Var y) const { return cost(x) < cost(y); }

         // TODO: investigate this order alternative more.
         // bool operator()(Var x, Var y) const {
         //     int c_x = cost(x);
         //     int c_y = cost(y);
         //     return c_x < c_y || c_x == c_y && x < y; }
     };

     struct ClauseDeleted {
         const ClauseAllocator& ca;
         explicit ClauseDeleted(const ClauseAllocator& _ca) : ca(_ca) {}
         bool operator()(const CRef& cr) const { return ca[cr].mark() == 1; } };

     // Solver state:
     //
     int                 elimorder;
     bool                use_simplification;
     Var                 max_simp_var;        // Max variable at the point simplification was turned off.
     vec<uint32_t>       elimclauses;
     VMap<char>          touched;
     OccLists<Var, vec<CRef>, ClauseDeleted>
                         occurs;
     LMap<int>           n_occ;
     Heap<Var,ElimLt>    elim_heap;
     Queue<CRef>         subsumption_queue;
     VMap<char>          frozen;
     vec<Var>            frozen_vars;
     VMap<char>          eliminated;
     int                 bwdsub_assigns;
     int                 n_touched;

     // Temporaries:
     //
     CRef                bwdsub_tmpunit;

     // Main internal methods:
     //
     lbool         solve_                   (bool do_simp = true, bool turn_off_simp = false);
     bool          asymm                    (Var v, CRef cr);
     bool          asymmVar                 (Var v);
     void          updateElimHeap           (Var v);
     void          gatherTouchedClauses     ();
     bool          merge                    (const Clause& _ps, const Clause& _qs, Var v, vec<Lit>& out_clause);
     bool          merge                    (const Clause& _ps, const Clause& _qs, Var v, int& size);
     bool          backwardSubsumptionCheck (bool verbose = false);
     bool          eliminateVar             (Var v);
     void          extendModel              ();

     void          removeClause             (CRef cr);
     bool          strengthenClause         (CRef cr, Lit l);
     bool          implied                  (const vec<Lit>& c);
     void          relocAll                 (ClauseAllocator& to);
 };


 //=================================================================================================
 // Implementation of inline methods:


 inline bool SimpSolver::isEliminated (Var v) const { return eliminated[v]; }
 inline void SimpSolver::updateElimHeap(Var v) {
     assert(use_simplification);
     // if (!frozen[v] && !isEliminated(v) && value(v) == l_Undef)
     if (elim_heap.inHeap(v) || (!frozen[v] && !isEliminated(v) && value(v) == l_Undef))
         elim_heap.update(v); }


 inline bool SimpSolver::addClause    (const vec<Lit>& ps)    { ps.copyTo(add_tmp); return addClause_(add_tmp); }
 inline bool SimpSolver::addEmptyClause()                     { add_tmp.clear(); return addClause_(add_tmp); }
 inline bool SimpSolver::addClause    (Lit p)                 { add_tmp.clear(); add_tmp.push(p); return addClause_(add_tmp); }
 inline bool SimpSolver::addClause    (Lit p, Lit q)          { add_tmp.clear(); add_tmp.push(p); add_tmp.push(q); return addClause_(add_tmp); }
 inline bool SimpSolver::addClause    (Lit p, Lit q, Lit r)   { add_tmp.clear(); add_tmp.push(p); add_tmp.push(q); add_tmp.push(r); return addClause_(add_tmp); }
 inline bool SimpSolver::addClause    (Lit p, Lit q, Lit r, Lit s){ add_tmp.clear(); add_tmp.push(p); add_tmp.push(q); add_tmp.push(r); add_tmp.push(s); return addClause_(add_tmp); }
 inline void SimpSolver::setFrozen    (Var v, bool b) { frozen[v] = (char)b; if (use_simplification && !b) { updateElimHeap(v); } }

 inline void SimpSolver::freezeVar(Var v){
     if (!frozen[v]){
         frozen[v] = 1;
         frozen_vars.push(v);
     } }

 inline void SimpSolver::thaw(){
     for (int i = 0; i < frozen_vars.size(); i++){
         Var v = frozen_vars[i];
         frozen[v] = 0;
         if (use_simplification)
             updateElimHeap(v);
     }
     frozen_vars.clear(); }

 inline bool SimpSolver::solve        (                     bool do_simp, bool turn_off_simp)  { budgetOff(); assumptions.clear(); return solve_(do_simp, turn_off_simp) == l_True; }
 inline bool SimpSolver::solve        (Lit p       ,        bool do_simp, bool turn_off_simp)  { budgetOff(); assumptions.clear(); assumptions.push(p); return solve_(do_simp, turn_off_simp) == l_True; }
 inline bool SimpSolver::solve        (Lit p, Lit q,        bool do_simp, bool turn_off_simp)  { budgetOff(); assumptions.clear(); assumptions.push(p); assumptions.push(q); return solve_(do_simp, turn_off_simp) == l_True; }
 inline bool SimpSolver::solve        (Lit p, Lit q, Lit r, bool do_simp, bool turn_off_simp)  { budgetOff(); assumptions.clear(); assumptions.push(p); assumptions.push(q); assumptions.push(r); return solve_(do_simp, turn_off_simp) == l_True; }
 inline bool SimpSolver::solve        (const vec<Lit>& assumps, bool do_simp, bool turn_off_simp){
     budgetOff(); assumps.copyTo(assumptions); return solve_(do_simp, turn_off_simp) == l_True; }

 inline lbool SimpSolver::solveLimited (const vec<Lit>& assumps, bool do_simp, bool turn_off_simp){
     assumps.copyTo(assumptions); return solve_(do_simp, turn_off_simp); }

 //=================================================================================================
 }

 #endif
	/************************************************************************************[SimpSolver.h]
	Copyright (c) 2006, Niklas Een, Niklas Sorensson
	Copyright (c) 2007-2010, Niklas Sorensson

	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 Minisat_SimpSolver_h
	#define Minisat_SimpSolver_h

	#include "Queue.h"
	#include "Solver.h"


	namespace Minisat {

	//=================================================================================================


	class SimpSolver : public Solver {
	public:
	// Constructor/Destructor:
	//
	SimpSolver();
	~SimpSolver();

	// Problem specification:
	//
	Var newVar (lbool upol = l_Undef, bool dvar = true);
	void releaseVar(Lit l);
	bool addClause (const vec<Lit>& ps);
	bool addEmptyClause(); // Add the empty clause to the solver.
	bool addClause (Lit p); // Add a unit clause to the solver.
	bool addClause (Lit p, Lit q); // Add a binary clause to the solver.
	bool addClause (Lit p, Lit q, Lit r); // Add a ternary clause to the solver.
	bool addClause (Lit p, Lit q, Lit r, Lit s); // Add a quaternary clause to the solver.
	bool addClause_( vec<Lit>& ps);
	bool substitute(Var v, Lit x); // Replace all occurences of v with x (may cause a contradiction).

	// Variable mode:
	//
	void setFrozen (Var v, bool b); // If a variable is frozen it will not be eliminated.
	bool isEliminated(Var v) const;

	// Alternative freeze interface (may replace 'setFrozen()'):
	void freezeVar (Var v); // Freeze one variable so it will not be eliminated.
	void thaw (); // Thaw all frozen variables.


	// Solving:
	//
	bool solve (const vec<Lit>& assumps, bool do_simp = true, bool turn_off_simp = false);
	lbool solveLimited(const vec<Lit>& assumps, bool do_simp = true, bool turn_off_simp = false);
	bool solve ( bool do_simp = true, bool turn_off_simp = false);
	bool solve (Lit p , bool do_simp = true, bool turn_off_simp = false);
	bool solve (Lit p, Lit q, bool do_simp = true, bool turn_off_simp = false);
	bool solve (Lit p, Lit q, Lit r, bool do_simp = true, bool turn_off_simp = false);
	bool eliminate (bool turn_off_elim = false); // Perform variable elimination based simplification.

	// Memory managment:
	//
	virtual void garbageCollect();


	// Generate a (possibly simplified) DIMACS file:
	//
	#if 0
	void toDimacs (const char* file, const vec<Lit>& assumps);
	void toDimacs (const char* file);
	void toDimacs (const char* file, Lit p);
	void toDimacs (const char* file, Lit p, Lit q);
	void toDimacs (const char* file, Lit p, Lit q, Lit r);
	#endif

	// Mode of operation:
	//
	int grow; // Allow a variable elimination step to grow by a number of clauses (default to zero).
	int clause_lim; // Variables are not eliminated if it produces a resolvent with a length above this limit.
	// -1 means no limit.
	int subsumption_lim; // Do not check if subsumption against a clause larger than this. -1 means no limit.
	double simp_garbage_frac; // A different limit for when to issue a GC during simplification (Also see 'garbage_frac').

	bool use_asymm; // Shrink clauses by asymmetric branching.
	bool use_rcheck; // Check if a clause is already implied. Prett costly, and subsumes subsumptions :)
	bool use_elim; // Perform variable elimination.
	bool extend_model; // Flag to indicate whether the user needs to look at the full model.

	// Statistics:
	//
	int merges;
	int asymm_lits;
	int eliminated_vars;

	protected:

	// Helper structures:
	//
	struct ElimLt {
	const LMap<int>& n_occ;
	explicit ElimLt(const LMap<int>& no) : n_occ(no) {}

	// TODO: are 64-bit operations here noticably bad on 32-bit platforms? Could use a saturating
	// 32-bit implementation instead then, but this will have to do for now.
	uint64_t cost (Var x) const { return (uint64_t)n_occ[mkLit(x)] * (uint64_t)n_occ[~mkLit(x)]; }
	bool operator()(Var x, Var y) const { return cost(x) < cost(y); }

	// TODO: investigate this order alternative more.
	// bool operator()(Var x, Var y) const {
	// int c_x = cost(x);
	// int c_y = cost(y);
	// return c_x < c_y \|\| c_x == c_y && x < y; }
	};

	struct ClauseDeleted {
	const ClauseAllocator& ca;
	explicit ClauseDeleted(const ClauseAllocator& _ca) : ca(_ca) {}
	bool operator()(const CRef& cr) const { return ca[cr].mark() == 1; } };

	// Solver state:
	//
	int elimorder;
	bool use_simplification;
	Var max_simp_var; // Max variable at the point simplification was turned off.
	vec<uint32_t> elimclauses;
	VMap<char> touched;
	OccLists<Var, vec<CRef>, ClauseDeleted>
	occurs;
	LMap<int> n_occ;
	Heap<Var,ElimLt> elim_heap;
	Queue<CRef> subsumption_queue;
	VMap<char> frozen;
	vec<Var> frozen_vars;
	VMap<char> eliminated;
	int bwdsub_assigns;
	int n_touched;

	// Temporaries:
	//
	CRef bwdsub_tmpunit;

	// Main internal methods:
	//
	lbool solve_ (bool do_simp = true, bool turn_off_simp = false);
	bool asymm (Var v, CRef cr);
	bool asymmVar (Var v);
	void updateElimHeap (Var v);
	void gatherTouchedClauses ();
	bool merge (const Clause& _ps, const Clause& _qs, Var v, vec<Lit>& out_clause);
	bool merge (const Clause& _ps, const Clause& _qs, Var v, int& size);
	bool backwardSubsumptionCheck (bool verbose = false);
	bool eliminateVar (Var v);
	void extendModel ();

	void removeClause (CRef cr);
	bool strengthenClause (CRef cr, Lit l);
	bool implied (const vec<Lit>& c);
	void relocAll (ClauseAllocator& to);
	};


	//=================================================================================================
	// Implementation of inline methods:


	inline bool SimpSolver::isEliminated (Var v) const { return eliminated[v]; }
	inline void SimpSolver::updateElimHeap(Var v) {
	assert(use_simplification);
	// if (!frozen[v] && !isEliminated(v) && value(v) == l_Undef)
	if (elim_heap.inHeap(v) \|\| (!frozen[v] && !isEliminated(v) && value(v) == l_Undef))
	elim_heap.update(v); }


	inline bool SimpSolver::addClause (const vec<Lit>& ps) { ps.copyTo(add_tmp); return addClause_(add_tmp); }
	inline bool SimpSolver::addEmptyClause() { add_tmp.clear(); return addClause_(add_tmp); }
	inline bool SimpSolver::addClause (Lit p) { add_tmp.clear(); add_tmp.push(p); return addClause_(add_tmp); }
	inline bool SimpSolver::addClause (Lit p, Lit q) { add_tmp.clear(); add_tmp.push(p); add_tmp.push(q); return addClause_(add_tmp); }
	inline bool SimpSolver::addClause (Lit p, Lit q, Lit r) { add_tmp.clear(); add_tmp.push(p); add_tmp.push(q); add_tmp.push(r); return addClause_(add_tmp); }
	inline bool SimpSolver::addClause (Lit p, Lit q, Lit r, Lit s){ add_tmp.clear(); add_tmp.push(p); add_tmp.push(q); add_tmp.push(r); add_tmp.push(s); return addClause_(add_tmp); }
	inline void SimpSolver::setFrozen (Var v, bool b) { frozen[v] = (char)b; if (use_simplification && !b) { updateElimHeap(v); } }

	inline void SimpSolver::freezeVar(Var v){
	if (!frozen[v]){
	frozen[v] = 1;
	frozen_vars.push(v);
	} }

	inline void SimpSolver::thaw(){
	for (int i = 0; i < frozen_vars.size(); i++){
	Var v = frozen_vars[i];
	frozen[v] = 0;
	if (use_simplification)
	updateElimHeap(v);
	}
	frozen_vars.clear(); }

	inline bool SimpSolver::solve ( bool do_simp, bool turn_off_simp) { budgetOff(); assumptions.clear(); return solve_(do_simp, turn_off_simp) == l_True; }
	inline bool SimpSolver::solve (Lit p , bool do_simp, bool turn_off_simp) { budgetOff(); assumptions.clear(); assumptions.push(p); return solve_(do_simp, turn_off_simp) == l_True; }
	inline bool SimpSolver::solve (Lit p, Lit q, bool do_simp, bool turn_off_simp) { budgetOff(); assumptions.clear(); assumptions.push(p); assumptions.push(q); return solve_(do_simp, turn_off_simp) == l_True; }
	inline bool SimpSolver::solve (Lit p, Lit q, Lit r, bool do_simp, bool turn_off_simp) { budgetOff(); assumptions.clear(); assumptions.push(p); assumptions.push(q); assumptions.push(r); return solve_(do_simp, turn_off_simp) == l_True; }
	inline bool SimpSolver::solve (const vec<Lit>& assumps, bool do_simp, bool turn_off_simp){
	budgetOff(); assumps.copyTo(assumptions); return solve_(do_simp, turn_off_simp) == l_True; }

	inline lbool SimpSolver::solveLimited (const vec<Lit>& assumps, bool do_simp, bool turn_off_simp){
	assumps.copyTo(assumptions); return solve_(do_simp, turn_off_simp); }

	//=================================================================================================
	}

	#endif