libs/minisat/SimpSolver.h

   1 /************************************************************************************[SimpSolver.h]
   2 Copyright (c) 2006,      Niklas Een, Niklas Sorensson
   3 Copyright (c) 2007-2010, Niklas Sorensson
   4
   5 Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
   6 associated documentation files (the "Software"), to deal in the Software without restriction,
   7 including without limitation the rights to use, copy, modify, merge, publish, distribute,
   8 sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
   9 furnished to do so, subject to the following conditions:
  10
  11 The above copyright notice and this permission notice shall be included in all copies or
  12 substantial portions of the Software.
  13
  14 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
  15 NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  16 NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
  17 DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
  18 OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  19 **************************************************************************************************/
  20
  21 #ifndef Minisat_SimpSolver_h
  22 #define Minisat_SimpSolver_h
  23
  24 #include "Queue.h"
  25 #include "Solver.h"
  26
  27
  28 namespace Minisat {
  29
  30 //=================================================================================================
  31
  32
  33 class SimpSolver : public Solver {
  34  public:
  35     // Constructor/Destructor:
  36     //
  37     SimpSolver();
  38     ~SimpSolver();
  39
  40     // Problem specification:
  41     //
  42     Var     newVar    (lbool upol = l_Undef, bool dvar = true);
  43     void    releaseVar(Lit l);
  44     bool    addClause (const vec<Lit>& ps);
  45     bool    addEmptyClause();                // Add the empty clause to the solver.
  46     bool    addClause (Lit p);               // Add a unit clause to the solver.
  47     bool    addClause (Lit p, Lit q);        // Add a binary clause to the solver.
  48     bool    addClause (Lit p, Lit q, Lit r); // Add a ternary clause to the solver.
  49     bool    addClause (Lit p, Lit q, Lit r, Lit s); // Add a quaternary clause to the solver.
  50     bool    addClause_(      vec<Lit>& ps);
  51     bool    substitute(Var v, Lit x);  // Replace all occurences of v with x (may cause a contradiction).
  52
  53     // Variable mode:
  54     //
  55     void    setFrozen (Var v, bool b); // If a variable is frozen it will not be eliminated.
  56     bool    isEliminated(Var v) const;
  57
  58     // Alternative freeze interface (may replace 'setFrozen()'):
  59     void    freezeVar (Var v);         // Freeze one variable so it will not be eliminated.
  60     void    thaw      ();              // Thaw all frozen variables.
  61
  62
  63     // Solving:
  64     //
  65     bool    solve       (const vec<Lit>& assumps, bool do_simp = true, bool turn_off_simp = false);
  66     lbool   solveLimited(const vec<Lit>& assumps, bool do_simp = true, bool turn_off_simp = false);
  67     bool    solve       (                     bool do_simp = true, bool turn_off_simp = false);
  68     bool    solve       (Lit p       ,        bool do_simp = true, bool turn_off_simp = false);
  69     bool    solve       (Lit p, Lit q,        bool do_simp = true, bool turn_off_simp = false);
  70     bool    solve       (Lit p, Lit q, Lit r, bool do_simp = true, bool turn_off_simp = false);
  71     bool    eliminate   (bool turn_off_elim = false);  // Perform variable elimination based simplification.
  72
  73     // Memory managment:
  74     //
  75     virtual void garbageCollect();
  76
  77
  78     // Generate a (possibly simplified) DIMACS file:
  79     //
  80 #if 0
  81     void    toDimacs  (const char* file, const vec<Lit>& assumps);
  82     void    toDimacs  (const char* file);
  83     void    toDimacs  (const char* file, Lit p);
  84     void    toDimacs  (const char* file, Lit p, Lit q);
  85     void    toDimacs  (const char* file, Lit p, Lit q, Lit r);
  86 #endif
  87
  88     // Mode of operation:
  89     //
  90     int     grow;              // Allow a variable elimination step to grow by a number of clauses (default to zero).
  91     int     clause_lim;        // Variables are not eliminated if it produces a resolvent with a length above this limit.
  92                                // -1 means no limit.
  93     int     subsumption_lim;   // Do not check if subsumption against a clause larger than this. -1 means no limit.
  94     double  simp_garbage_frac; // A different limit for when to issue a GC during simplification (Also see 'garbage_frac').
  95
  96     bool    use_asymm;         // Shrink clauses by asymmetric branching.
  97     bool    use_rcheck;        // Check if a clause is already implied. Prett costly, and subsumes subsumptions :)
  98     bool    use_elim;          // Perform variable elimination.
  99     bool    extend_model;      // Flag to indicate whether the user needs to look at the full model.
 100
 101     // Statistics:
 102     //
 103     int     merges;
 104     int     asymm_lits;
 105     int     eliminated_vars;
 106
 107  protected:
 108
 109     // Helper structures:
 110     //
 111     struct ElimLt {
 112         const LMap<int>& n_occ;
 113         explicit ElimLt(const LMap<int>& no) : n_occ(no) {}
 114
 115         // TODO: are 64-bit operations here noticably bad on 32-bit platforms? Could use a saturating
 116         // 32-bit implementation instead then, but this will have to do for now.
 117         uint64_t cost  (Var x)        const { return (uint64_t)n_occ[mkLit(x)] * (uint64_t)n_occ[~mkLit(x)]; }
 118         bool operator()(Var x, Var y) const { return cost(x) < cost(y); }
 119
 120         // TODO: investigate this order alternative more.
 121         // bool operator()(Var x, Var y) const {
 122         //     int c_x = cost(x);
 123         //     int c_y = cost(y);
 124         //     return c_x < c_y || c_x == c_y && x < y; }
 125     };
 126
 127     struct ClauseDeleted {
 128         const ClauseAllocator& ca;
 129         explicit ClauseDeleted(const ClauseAllocator& _ca) : ca(_ca) {}
 130         bool operator()(const CRef& cr) const { return ca[cr].mark() == 1; } };
 131
 132     // Solver state:
 133     //
 134     int                 elimorder;
 135     bool                use_simplification;
 136     Var                 max_simp_var;        // Max variable at the point simplification was turned off.
 137     vec<uint32_t>       elimclauses;
 138     VMap<char>          touched;
 139     OccLists<Var, vec<CRef>, ClauseDeleted>
 140                         occurs;
 141     LMap<int>           n_occ;
 142     Heap<Var,ElimLt>    elim_heap;
 143     Queue<CRef>         subsumption_queue;
 144     VMap<char>          frozen;
 145     vec<Var>            frozen_vars;
 146     VMap<char>          eliminated;
 147     int                 bwdsub_assigns;
 148     int                 n_touched;
 149
 150     // Temporaries:
 151     //
 152     CRef                bwdsub_tmpunit;
 153
 154     // Main internal methods:
 155     //
 156     lbool         solve_                   (bool do_simp = true, bool turn_off_simp = false);
 157     bool          asymm                    (Var v, CRef cr);
 158     bool          asymmVar                 (Var v);
 159     void          updateElimHeap           (Var v);
 160     void          gatherTouchedClauses     ();
 161     bool          merge                    (const Clause& _ps, const Clause& _qs, Var v, vec<Lit>& out_clause);
 162     bool          merge                    (const Clause& _ps, const Clause& _qs, Var v, int& size);
 163     bool          backwardSubsumptionCheck (bool verbose = false);
 164     bool          eliminateVar             (Var v);
 165     void          extendModel              ();
 166
 167     void          removeClause             (CRef cr);
 168     bool          strengthenClause         (CRef cr, Lit l);
 169     bool          implied                  (const vec<Lit>& c);
 170     void          relocAll                 (ClauseAllocator& to);
 171 };
 172
 173
 174 //=================================================================================================
 175 // Implementation of inline methods:
 176
 177
 178 inline bool SimpSolver::isEliminated (Var v) const { return eliminated[v]; }
 179 inline void SimpSolver::updateElimHeap(Var v) {
 180     assert(use_simplification);
 181     // if (!frozen[v] && !isEliminated(v) && value(v) == l_Undef)
 182     if (elim_heap.inHeap(v) || (!frozen[v] && !isEliminated(v) && value(v) == l_Undef))
 183         elim_heap.update(v); }
 184
 185
 186 inline bool SimpSolver::addClause    (const vec<Lit>& ps)    { ps.copyTo(add_tmp); return addClause_(add_tmp); }
 187 inline bool SimpSolver::addEmptyClause()                     { add_tmp.clear(); return addClause_(add_tmp); }
 188 inline bool SimpSolver::addClause    (Lit p)                 { add_tmp.clear(); add_tmp.push(p); return addClause_(add_tmp); }
 189 inline bool SimpSolver::addClause    (Lit p, Lit q)          { add_tmp.clear(); add_tmp.push(p); add_tmp.push(q); return addClause_(add_tmp); }
 190 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); }
 191 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); }
 192 inline void SimpSolver::setFrozen    (Var v, bool b) { frozen[v] = (char)b; if (use_simplification && !b) { updateElimHeap(v); } }
 193
 194 inline void SimpSolver::freezeVar(Var v){
 195     if (!frozen[v]){
 196         frozen[v] = 1;
 197         frozen_vars.push(v);
 198     } }
 199
 200 inline void SimpSolver::thaw(){
 201     for (int i = 0; i < frozen_vars.size(); i++){
 202         Var v = frozen_vars[i];
 203         frozen[v] = 0;
 204         if (use_simplification)
 205             updateElimHeap(v);
 206     }
 207     frozen_vars.clear(); }
 208
 209 inline bool SimpSolver::solve        (                     bool do_simp, bool turn_off_simp)  { budgetOff(); assumptions.clear(); return solve_(do_simp, turn_off_simp) == l_True; }
 210 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; }
 211 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; }
 212 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; }
 213 inline bool SimpSolver::solve        (const vec<Lit>& assumps, bool do_simp, bool turn_off_simp){
 214     budgetOff(); assumps.copyTo(assumptions); return solve_(do_simp, turn_off_simp) == l_True; }
 215
 216 inline lbool SimpSolver::solveLimited (const vec<Lit>& assumps, bool do_simp, bool turn_off_simp){
 217     assumps.copyTo(assumptions); return solve_(do_simp, turn_off_simp); }
 218
 219 //=================================================================================================
 220 }
 221
 222 #endif