374 lines
21 KiB
C++
Executable File
374 lines
21 KiB
C++
Executable File
/****************************************************************************************[Solver.h]
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Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
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Copyright (c) 2007-2010, Niklas Sorensson
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Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
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associated documentation files (the "Software"), to deal in the Software without restriction,
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including without limitation the rights to use, copy, modify, merge, publish, distribute,
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sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all copies or
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substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
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NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
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DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
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OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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**************************************************************************************************/
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#ifndef Minisat_Solver_h
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#define Minisat_Solver_h
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#include "mtl/Vec.h"
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#include "mtl/Heap.h"
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#include "mtl/Alg.h"
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#include "utils/Options.h"
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#include "core/SolverTypes.h"
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namespace Minisat {
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//=================================================================================================
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// Solver -- the main class:
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class Solver {
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public:
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// Constructor/Destructor:
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//
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Solver();
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virtual ~Solver();
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// Problem specification:
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//
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Var newVar (bool polarity = true, bool dvar = true); // Add a new variable with parameters specifying variable mode.
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bool addClause (const vec<Lit>& ps); // Add a clause to the solver.
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bool addEmptyClause(); // Add the empty clause, making the solver contradictory.
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bool addClause (Lit p); // Add a unit clause to the solver.
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bool addClause (Lit p, Lit q); // Add a binary clause to the solver.
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bool addClause (Lit p, Lit q, Lit r); // Add a ternary clause to the solver.
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bool addClause_( vec<Lit>& ps); // Add a clause to the solver without making superflous internal copy. Will
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// change the passed vector 'ps'.
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// Solving:
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//
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bool simplify (); // Removes already satisfied clauses.
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bool solve (const vec<Lit>& assumps); // Search for a model that respects a given set of assumptions.
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lbool solveLimited (const vec<Lit>& assumps); // Search for a model that respects a given set of assumptions (With resource constraints).
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bool solve (); // Search without assumptions.
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bool solve (Lit p); // Search for a model that respects a single assumption.
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bool solve (Lit p, Lit q); // Search for a model that respects two assumptions.
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bool solve (Lit p, Lit q, Lit r); // Search for a model that respects three assumptions.
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bool okay () const; // FALSE means solver is in a conflicting state
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void toDimacs (FILE* f, const vec<Lit>& assumps); // Write CNF to file in DIMACS-format.
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void toDimacs (const char *file, const vec<Lit>& assumps);
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void toDimacs (FILE* f, Clause& c, vec<Var>& map, Var& max);
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// Convenience versions of 'toDimacs()':
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void toDimacs (const char* file);
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void toDimacs (const char* file, Lit p);
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void toDimacs (const char* file, Lit p, Lit q);
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void toDimacs (const char* file, Lit p, Lit q, Lit r);
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// Variable mode:
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//
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void setPolarity (Var v, bool b); // Declare which polarity the decision heuristic should use for a variable. Requires mode 'polarity_user'.
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void setDecisionVar (Var v, bool b); // Declare if a variable should be eligible for selection in the decision heuristic.
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// Read state:
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//
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lbool value (Var x) const; // The current value of a variable.
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lbool value (Lit p) const; // The current value of a literal.
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lbool modelValue (Var x) const; // The value of a variable in the last model. The last call to solve must have been satisfiable.
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lbool modelValue (Lit p) const; // The value of a literal in the last model. The last call to solve must have been satisfiable.
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int nAssigns () const; // The current number of assigned literals.
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int nClauses () const; // The current number of original clauses.
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int nLearnts () const; // The current number of learnt clauses.
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int nVars () const; // The current number of variables.
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int nFreeVars () const;
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// Resource contraints:
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//
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void setConfBudget(int64_t x);
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void setPropBudget(int64_t x);
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void budgetOff();
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void interrupt(); // Trigger a (potentially asynchronous) interruption of the solver.
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void clearInterrupt(); // Clear interrupt indicator flag.
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// Memory managment:
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//
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virtual void garbageCollect();
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void checkGarbage(double gf);
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void checkGarbage();
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// Extra results: (read-only member variable)
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//
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vec<lbool> model; // If problem is satisfiable, this vector contains the model (if any).
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vec<Lit> conflict; // If problem is unsatisfiable (possibly under assumptions),
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// this vector represent the final conflict clause expressed in the assumptions.
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// Mode of operation:
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//
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int verbosity;
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double var_decay;
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double clause_decay;
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double random_var_freq;
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double random_seed;
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bool luby_restart;
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int ccmin_mode; // Controls conflict clause minimization (0=none, 1=basic, 2=deep).
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int phase_saving; // Controls the level of phase saving (0=none, 1=limited, 2=full).
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bool rnd_pol; // Use random polarities for branching heuristics.
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bool rnd_init_act; // Initialize variable activities with a small random value.
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double garbage_frac; // The fraction of wasted memory allowed before a garbage collection is triggered.
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int restart_first; // The initial restart limit. (default 100)
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double restart_inc; // The factor with which the restart limit is multiplied in each restart. (default 1.5)
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double learntsize_factor; // The intitial limit for learnt clauses is a factor of the original clauses. (default 1 / 3)
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double learntsize_inc; // The limit for learnt clauses is multiplied with this factor each restart. (default 1.1)
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int learntsize_adjust_start_confl;
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double learntsize_adjust_inc;
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// Statistics: (read-only member variable)
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//
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uint64_t solves, starts, decisions, rnd_decisions, propagations, conflicts;
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uint64_t dec_vars, clauses_literals, learnts_literals, max_literals, tot_literals;
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protected:
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// Helper structures:
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//
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struct VarData { CRef reason; int level; };
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static inline VarData mkVarData(CRef cr, int l){ VarData d = {cr, l}; return d; }
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struct Watcher {
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CRef cref;
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Lit blocker;
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Watcher(CRef cr, Lit p) : cref(cr), blocker(p) {}
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bool operator==(const Watcher& w) const { return cref == w.cref; }
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bool operator!=(const Watcher& w) const { return cref != w.cref; }
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};
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struct WatcherDeleted
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{
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const ClauseAllocator& ca;
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WatcherDeleted(const ClauseAllocator& _ca) : ca(_ca) {}
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bool operator()(const Watcher& w) const { return ca[w.cref].mark() == 1; }
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};
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struct VarOrderLt {
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const vec<double>& activity;
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bool operator () (Var x, Var y) const { return activity[x] > activity[y]; }
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VarOrderLt(const vec<double>& act) : activity(act) { }
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};
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// Solver state:
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//
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bool ok; // If FALSE, the constraints are already unsatisfiable. No part of the solver state may be used!
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vec<CRef> clauses; // List of problem clauses.
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vec<CRef> learnts; // List of learnt clauses.
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double cla_inc; // Amount to bump next clause with.
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vec<double> activity; // A heuristic measurement of the activity of a variable.
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double var_inc; // Amount to bump next variable with.
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OccLists<Lit, vec<Watcher>, WatcherDeleted>
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watches; // 'watches[lit]' is a list of constraints watching 'lit' (will go there if literal becomes true).
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vec<lbool> assigns; // The current assignments.
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vec<char> polarity; // The preferred polarity of each variable.
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vec<char> decision; // Declares if a variable is eligible for selection in the decision heuristic.
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vec<Lit> trail; // Assignment stack; stores all assigments made in the order they were made.
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vec<int> trail_lim; // Separator indices for different decision levels in 'trail'.
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vec<VarData> vardata; // Stores reason and level for each variable.
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int qhead; // Head of queue (as index into the trail -- no more explicit propagation queue in MiniSat).
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int simpDB_assigns; // Number of top-level assignments since last execution of 'simplify()'.
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int64_t simpDB_props; // Remaining number of propagations that must be made before next execution of 'simplify()'.
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vec<Lit> assumptions; // Current set of assumptions provided to solve by the user.
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Heap<VarOrderLt> order_heap; // A priority queue of variables ordered with respect to the variable activity.
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double progress_estimate;// Set by 'search()'.
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bool remove_satisfied; // Indicates whether possibly inefficient linear scan for satisfied clauses should be performed in 'simplify'.
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ClauseAllocator ca;
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// Temporaries (to reduce allocation overhead). Each variable is prefixed by the method in which it is
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// used, exept 'seen' wich is used in several places.
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//
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vec<char> seen;
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vec<Lit> analyze_stack;
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vec<Lit> analyze_toclear;
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vec<Lit> add_tmp;
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double max_learnts;
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double learntsize_adjust_confl;
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int learntsize_adjust_cnt;
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// Resource contraints:
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//
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int64_t conflict_budget; // -1 means no budget.
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int64_t propagation_budget; // -1 means no budget.
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bool asynch_interrupt;
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// Main internal methods:
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//
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void insertVarOrder (Var x); // Insert a variable in the decision order priority queue.
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Lit pickBranchLit (); // Return the next decision variable.
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void newDecisionLevel (); // Begins a new decision level.
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void uncheckedEnqueue (Lit p, CRef from = CRef_Undef); // Enqueue a literal. Assumes value of literal is undefined.
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bool enqueue (Lit p, CRef from = CRef_Undef); // Test if fact 'p' contradicts current state, enqueue otherwise.
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CRef propagate (); // Perform unit propagation. Returns possibly conflicting clause.
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void cancelUntil (int level); // Backtrack until a certain level.
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void analyze (CRef confl, vec<Lit>& out_learnt, int& out_btlevel); // (bt = backtrack)
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void analyzeFinal (Lit p, vec<Lit>& out_conflict); // COULD THIS BE IMPLEMENTED BY THE ORDINARIY "analyze" BY SOME REASONABLE GENERALIZATION?
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bool litRedundant (Lit p, uint32_t abstract_levels); // (helper method for 'analyze()')
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lbool search (int nof_conflicts); // Search for a given number of conflicts.
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lbool solve_ (); // Main solve method (assumptions given in 'assumptions').
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void reduceDB (); // Reduce the set of learnt clauses.
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void removeSatisfied (vec<CRef>& cs); // Shrink 'cs' to contain only non-satisfied clauses.
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void rebuildOrderHeap ();
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// Maintaining Variable/Clause activity:
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//
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void varDecayActivity (); // Decay all variables with the specified factor. Implemented by increasing the 'bump' value instead.
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void varBumpActivity (Var v, double inc); // Increase a variable with the current 'bump' value.
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void varBumpActivity (Var v); // Increase a variable with the current 'bump' value.
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void claDecayActivity (); // Decay all clauses with the specified factor. Implemented by increasing the 'bump' value instead.
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void claBumpActivity (Clause& c); // Increase a clause with the current 'bump' value.
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// Operations on clauses:
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//
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void attachClause (CRef cr); // Attach a clause to watcher lists.
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void detachClause (CRef cr, bool strict = false); // Detach a clause to watcher lists.
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void removeClause (CRef cr); // Detach and free a clause.
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bool locked (const Clause& c) const; // Returns TRUE if a clause is a reason for some implication in the current state.
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bool satisfied (const Clause& c) const; // Returns TRUE if a clause is satisfied in the current state.
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void relocAll (ClauseAllocator& to);
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// Misc:
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//
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int decisionLevel () const; // Gives the current decisionlevel.
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uint32_t abstractLevel (Var x) const; // Used to represent an abstraction of sets of decision levels.
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CRef reason (Var x) const;
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int level (Var x) const;
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double progressEstimate () const; // DELETE THIS ?? IT'S NOT VERY USEFUL ...
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bool withinBudget () const;
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// Static helpers:
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//
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// Returns a random float 0 <= x < 1. Seed must never be 0.
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static inline double drand(double& seed) {
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seed *= 1389796;
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int q = (int)(seed / 2147483647);
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seed -= (double)q * 2147483647;
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return seed / 2147483647; }
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// Returns a random integer 0 <= x < size. Seed must never be 0.
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static inline int irand(double& seed, int size) {
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return (int)(drand(seed) * size); }
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};
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//=================================================================================================
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// Implementation of inline methods:
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inline CRef Solver::reason(Var x) const { return vardata[x].reason; }
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inline int Solver::level (Var x) const { return vardata[x].level; }
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inline void Solver::insertVarOrder(Var x) {
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if (!order_heap.inHeap(x) && decision[x]) order_heap.insert(x); }
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inline void Solver::varDecayActivity() { var_inc *= (1 / var_decay); }
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inline void Solver::varBumpActivity(Var v) { varBumpActivity(v, var_inc); }
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inline void Solver::varBumpActivity(Var v, double inc) {
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if ( (activity[v] += inc) > 1e100 ) {
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// Rescale:
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for (int i = 0; i < nVars(); i++)
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activity[i] *= 1e-100;
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var_inc *= 1e-100; }
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// Update order_heap with respect to new activity:
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if (order_heap.inHeap(v))
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order_heap.decrease(v); }
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inline void Solver::claDecayActivity() { cla_inc *= (1 / clause_decay); }
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inline void Solver::claBumpActivity (Clause& c) {
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if ( (c.activity() += cla_inc) > 1e20 ) {
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// Rescale:
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for (int i = 0; i < learnts.size(); i++)
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ca[learnts[i]].activity() *= 1e-20;
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cla_inc *= 1e-20; } }
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inline void Solver::checkGarbage(void){ return checkGarbage(garbage_frac); }
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inline void Solver::checkGarbage(double gf){
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if (ca.wasted() > ca.size() * gf)
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garbageCollect(); }
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// NOTE: enqueue does not set the ok flag! (only public methods do)
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inline bool Solver::enqueue (Lit p, CRef from) { return value(p) != l_Undef ? value(p) != l_False : (uncheckedEnqueue(p, from), true); }
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inline bool Solver::addClause (const vec<Lit>& ps) { ps.copyTo(add_tmp); return addClause_(add_tmp); }
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inline bool Solver::addEmptyClause () { add_tmp.clear(); return addClause_(add_tmp); }
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inline bool Solver::addClause (Lit p) { add_tmp.clear(); add_tmp.push(p); return addClause_(add_tmp); }
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inline bool Solver::addClause (Lit p, Lit q) { add_tmp.clear(); add_tmp.push(p); add_tmp.push(q); return addClause_(add_tmp); }
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inline bool Solver::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); }
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inline bool Solver::locked (const Clause& c) const { return value(c[0]) == l_True && reason(var(c[0])) != CRef_Undef && ca.lea(reason(var(c[0]))) == &c; }
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inline void Solver::newDecisionLevel() { trail_lim.push(trail.size()); }
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inline int Solver::decisionLevel () const { return trail_lim.size(); }
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inline uint32_t Solver::abstractLevel (Var x) const { return 1 << (level(x) & 31); }
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inline lbool Solver::value (Var x) const { return assigns[x]; }
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inline lbool Solver::value (Lit p) const { return assigns[var(p)] ^ sign(p); }
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inline lbool Solver::modelValue (Var x) const { return model[x]; }
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inline lbool Solver::modelValue (Lit p) const { return model[var(p)] ^ sign(p); }
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inline int Solver::nAssigns () const { return trail.size(); }
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inline int Solver::nClauses () const { return clauses.size(); }
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inline int Solver::nLearnts () const { return learnts.size(); }
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inline int Solver::nVars () const { return vardata.size(); }
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inline int Solver::nFreeVars () const { return (int)dec_vars - (trail_lim.size() == 0 ? trail.size() : trail_lim[0]); }
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inline void Solver::setPolarity (Var v, bool b) { polarity[v] = b; }
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inline void Solver::setDecisionVar(Var v, bool b)
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{
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if ( b && !decision[v]) dec_vars++;
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else if (!b && decision[v]) dec_vars--;
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decision[v] = b;
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insertVarOrder(v);
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}
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inline void Solver::setConfBudget(int64_t x){ conflict_budget = conflicts + x; }
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inline void Solver::setPropBudget(int64_t x){ propagation_budget = propagations + x; }
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inline void Solver::interrupt(){ asynch_interrupt = true; }
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inline void Solver::clearInterrupt(){ asynch_interrupt = false; }
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inline void Solver::budgetOff(){ conflict_budget = propagation_budget = -1; }
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inline bool Solver::withinBudget() const {
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return !asynch_interrupt &&
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(conflict_budget < 0 || conflicts < (uint64_t)conflict_budget) &&
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(propagation_budget < 0 || propagations < (uint64_t)propagation_budget); }
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// FIXME: after the introduction of asynchronous interrruptions the solve-versions that return a
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// pure bool do not give a safe interface. Either interrupts must be possible to turn off here, or
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// all calls to solve must return an 'lbool'. I'm not yet sure which I prefer.
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inline bool Solver::solve () { budgetOff(); assumptions.clear(); return solve_() == l_True; }
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inline bool Solver::solve (Lit p) { budgetOff(); assumptions.clear(); assumptions.push(p); return solve_() == l_True; }
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inline bool Solver::solve (Lit p, Lit q) { budgetOff(); assumptions.clear(); assumptions.push(p); assumptions.push(q); return solve_() == l_True; }
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inline bool Solver::solve (Lit p, Lit q, Lit r) { budgetOff(); assumptions.clear(); assumptions.push(p); assumptions.push(q); assumptions.push(r); return solve_() == l_True; }
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inline bool Solver::solve (const vec<Lit>& assumps){ budgetOff(); assumps.copyTo(assumptions); return solve_() == l_True; }
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inline lbool Solver::solveLimited (const vec<Lit>& assumps){ assumps.copyTo(assumptions); return solve_(); }
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inline bool Solver::okay () const { return ok; }
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inline void Solver::toDimacs (const char* file){ vec<Lit> as; toDimacs(file, as); }
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inline void Solver::toDimacs (const char* file, Lit p){ vec<Lit> as; as.push(p); toDimacs(file, as); }
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inline void Solver::toDimacs (const char* file, Lit p, Lit q){ vec<Lit> as; as.push(p); as.push(q); toDimacs(file, as); }
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inline void Solver::toDimacs (const char* file, Lit p, Lit q, Lit r){ vec<Lit> as; as.push(p); as.push(q); as.push(r); toDimacs(file, as); }
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//=================================================================================================
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// Debug etc:
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//=================================================================================================
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}
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#endif
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