src/sat/minisat/core/SolverTypes.h

   1 /***********************************************************************************[SolverTypes.h]
   2 MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
   3
   4 Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
   5 associated documentation files (the "Software"), to deal in the Software without restriction,
   6 including without limitation the rights to use, copy, modify, merge, publish, distribute,
   7 sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
   8 furnished to do so, subject to the following conditions:
   9
  10 The above copyright notice and this permission notice shall be included in all copies or
  11 substantial portions of the Software.
  12
  13 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
  14 NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  15 NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
  16 DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
  17 OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  18 **************************************************************************************************/
  19
  20 #ifndef CVC4_MiniSat_SolverTypes_h
  21 #define CVC4_MiniSat_SolverTypes_h
  22
  23 #include <cassert>
  24 #include <stdint.h>
  25
  26 namespace CVC4 {
  27 namespace MiniSat {
  28
  29 //=================================================================================================
  30 // Variables, literals, lifted booleans, clauses:
  31
  32
  33 // NOTE! Variables are just integers. No abstraction here. They should be chosen from 0..N,
  34 // so that they can be used as array indices.
  35
  36 typedef int Var;
  37 #define var_Undef (-1)
  38
  39
  40 class Lit {
  41     int     x;
  42  public:
  43     Lit() : x(2*var_Undef)                                              { }   // (lit_Undef)
  44     explicit Lit(Var var, bool sign = false) : x((var+var) + (int)sign) { }
  45
  46     // Don't use these for constructing/deconstructing literals. Use the normal constructors instead.
  47     friend int  toInt       (Lit p);  // Guarantees small, positive integers suitable for array indexing.
  48     friend Lit  toLit       (int i);  // Inverse of 'toInt()'
  49     friend Lit  operator   ~(Lit p);
  50     friend bool sign        (Lit p);
  51     friend int  var         (Lit p);
  52     friend Lit  unsign      (Lit p);
  53     friend Lit  id          (Lit p, bool sgn);
  54
  55     bool operator == (Lit p) const { return x == p.x; }
  56     bool operator != (Lit p) const { return x != p.x; }
  57     bool operator <  (Lit p) const { return x < p.x;  } // '<' guarantees that p, ~p are adjacent in the ordering.
  58 };
  59
  60 inline  int  toInt       (Lit p)           { return p.x; }
  61 inline  Lit  toLit       (int i)           { Lit p; p.x = i; return p; }
  62 inline  Lit  operator   ~(Lit p)           { Lit q; q.x = p.x ^ 1; return q; }
  63 inline  bool sign        (Lit p)           { return p.x & 1; }
  64 inline  int  var         (Lit p)           { return p.x >> 1; }
  65 inline  Lit  unsign      (Lit p)           { Lit q; q.x = p.x & ~1; return q; }
  66 inline  Lit  id          (Lit p, bool sgn) { Lit q; q.x = p.x ^ (int)sgn; return q; }
  67
  68 const Lit lit_Undef(var_Undef, false);  // }- Useful special constants.
  69 const Lit lit_Error(var_Undef, true );  // }
  70
  71
  72 //=================================================================================================
  73 // Lifted booleans:
  74
  75
  76 class lbool {
  77     char     value;
  78     explicit lbool(int v) : value(v) { }
  79
  80 public:
  81     lbool()       : value(0) { }
  82     lbool(bool x) : value((int)x*2-1) { }
  83     int toInt(void) const { return value; }
  84
  85     bool  operator == (lbool b) const { return value == b.value; }
  86     bool  operator != (lbool b) const { return value != b.value; }
  87     lbool operator ^ (bool b) const { return b ? lbool(-value) : lbool(value); }
  88
  89     friend int   toInt  (lbool l);
  90     friend lbool toLbool(int   v);
  91 };
  92 inline int   toInt  (lbool l) { return l.toInt(); }
  93 inline lbool toLbool(int   v) { return lbool(v);  }
  94
  95 const lbool l_True  = toLbool( 1);
  96 const lbool l_False = toLbool(-1);
  97 const lbool l_Undef = toLbool( 0);
  98
  99 //=================================================================================================
 100 // Clause -- a simple class for representing a clause:
 101
 102
 103 class Clause {
 104     uint32_t size_etc;
 105     union { float act; uint32_t abst; } extra;
 106     Lit     data[0];
 107
 108 public:
 109     void calcAbstraction() {
 110         uint32_t abstraction = 0;
 111         for (int i = 0; i < size(); i++)
 112             abstraction |= 1 << (var(data[i]) & 31);
 113         extra.abst = abstraction;  }
 114
 115     // NOTE: This constructor cannot be used directly (doesn't allocate enough memory).
 116     template<class V>
 117     Clause(const V& ps, bool learnt) {
 118         size_etc = (ps.size() << 3) | (uint32_t)learnt;
 119         for (int i = 0; i < ps.size(); i++) data[i] = ps[i];
 120         if (learnt) extra.act = 0; else calcAbstraction(); }
 121
 122     // -- use this function instead:
 123     template<class V>
 124     friend Clause* Clause_new(const V& ps, bool learnt = false) {
 125         assert(sizeof(Lit)      == sizeof(uint32_t));
 126         assert(sizeof(float)    == sizeof(uint32_t));
 127         void* mem = malloc(sizeof(Clause) + sizeof(uint32_t)*(ps.size()));
 128         return new (mem) Clause(ps, learnt); }
 129
 130     int          size        ()      const   { return size_etc >> 3; }
 131     void         shrink      (int i)         { assert(i <= size()); size_etc = (((size_etc >> 3) - i) << 3) | (size_etc & 7); }
 132     void         pop         ()              { shrink(1); }
 133     bool         learnt      ()      const   { return size_etc & 1; }
 134     uint32_t     mark        ()      const   { return (size_etc >> 1) & 3; }
 135     void         mark        (uint32_t m)    { size_etc = (size_etc & ~6) | ((m & 3) << 1); }
 136     const Lit&   last        ()      const   { return data[size()-1]; }
 137
 138     // NOTE: somewhat unsafe to change the clause in-place! Must manually call 'calcAbstraction' afterwards for
 139     //       subsumption operations to behave correctly.
 140     Lit&         operator [] (int i)         { return data[i]; }
 141     Lit          operator [] (int i) const   { return data[i]; }
 142     operator const Lit* (void) const         { return data; }
 143
 144     float&       activity    ()              { return extra.act; }
 145     uint32_t     abstraction () const { return extra.abst; }
 146
 147     Lit          subsumes    (const Clause& other) const;
 148     void         strengthen  (Lit p);
 149 };
 150
 151
 152 /*_________________________________________________________________________________________________
 153 |
 154 |  subsumes : (other : const Clause&)  ->  Lit
 155 |
 156 |  Description:
 157 |       Checks if clause subsumes 'other', and at the same time, if it can be used to simplify 'other'
 158 |       by subsumption resolution.
 159 |
 160 |    Result:
 161 |       lit_Error  - No subsumption or simplification
 162 |       lit_Undef  - Clause subsumes 'other'
 163 |       p          - The literal p can be deleted from 'other'
 164 |________________________________________________________________________________________________@*/
 165 inline Lit Clause::subsumes(const Clause& other) const
 166 {
 167     if (other.size() < size() || (extra.abst & ~other.extra.abst) != 0)
 168         return lit_Error;
 169
 170     Lit        ret = lit_Undef;
 171     const Lit* c  = (const Lit*)(*this);
 172     const Lit* d  = (const Lit*)other;
 173
 174     for (int i = 0; i < size(); i++) {
 175         // search for c[i] or ~c[i]
 176         for (int j = 0; j < other.size(); j++)
 177             if (c[i] == d[j])
 178                 goto ok;
 179             else if (ret == lit_Undef && c[i] == ~d[j]){
 180                 ret = c[i];
 181                 goto ok;
 182             }
 183
 184         // did not find it
 185         return lit_Error;
 186     ok:;
 187     }
 188
 189     return ret;
 190 }
 191
 192
 193 inline void Clause::strengthen(Lit p)
 194 {
 195     remove(*this, p);
 196     calcAbstraction();
 197 }
 198
 199 }/* CVC4::MiniSat namespace */
 200 }/* CVC4 namespace */
 201
 202 #endif /* CVC4_MiniSat_SolverTypes_h */