simpsolver.c

多核环境下运行了可满足性分析的工具软件

/************************************************************************************[SimpSolver.C]
MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
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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,
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OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
**************************************************************************************************/

#include "Sort.h"
#include "SimpSolver.h"
#include <iostream>

namespace minisat {

  //=================================================================================================
  // Constructor/Destructor:
  

  SimpSolver::SimpSolver() :
    grow               (0)
    , asymm_mode         (false)
    , redundancy_check   (false)
    , merges             (0)
    , asymm_lits         (0)
    , remembered_clauses (0)
    , elimorder          (1)
    , use_simplification (true)
    , elim_heap          (ElimLt(n_occ))
    , bwdsub_assigns     (0)
  {
    vec<Lit> dummy(1,lit_Undef);
    bwdsub_tmpunit   = Clause_new(dummy);
    remove_satisfied = false;
  }


  SimpSolver::~SimpSolver()
  {
    free(bwdsub_tmpunit);
    
    // NOTE: elimtable.size() might be lower than nVars() at the moment
    for (int i = 0; i < elimtable.size(); i++)
      for (int j = 0; j < elimtable[i].eliminated.size(); j++)
	free(elimtable[i].eliminated[j]);
  }
  
  
  Var SimpSolver::newVar(bool sign, bool dvar) {
    Var v = Solver::newVar(sign, dvar);
    
    if (use_simplification){
      n_occ    .push(0);
      n_occ    .push(0);
      occurs   .push();
      frozen   .push((char)false);
      touched  .push(0); 
      elim_heap.insert(v);
      elimtable.push();
    }
    return v; }
  
  bool SimpSolver::solve(bool do_simp, bool turn_off_simp) {
    bool     result = true;
    
    do_simp &= use_simplification;
    
    if (do_simp){
      result = eliminate(turn_off_simp);
      litToint();
    }
    
    return result;
  }
  
  
  bool SimpSolver::addClause(vec<Lit>& ps)
  {
    for (int i = 0; i < ps.size(); i++)
      if (isEliminated(var(ps[i])))
	remember(var(ps[i]));
    
    int nclauses = clauses.size();

    if (redundancy_check && implied(ps))
      return true;
    
    if (!Solver::addClause(ps))
      return false;
    
    if (use_simplification && clauses.size() == nclauses + 1){
      Clause& c = *clauses.last();

      subsumption_queue.insert(&c); // Alle Kandidaten f"ur subsumption sind in subsumption_queue
      
      for (int i = 0; i < c.size(); i++){
	assert(occurs.size() > var(c[i]));
	assert(!find(occurs[var(c[i])], &c));
	
	occurs[var(c[i])].push(&c);
	n_occ[toInt(c[i])]++; // Number of occurences von der Variablen c[i]
	touched[var(c[i])] = 1; // Variable in der added-Klausel
	assert(elimtable[var(c[i])].order == 0);
	if (elim_heap.inHeap(var(c[i])))
	  elim_heap.increase_(var(c[i]));
      }
    }
    
    return true;
  }


  void SimpSolver::removeClause(Clause& c)
  {
    assert(!c.learnt());
    
    if (use_simplification)
      for (int i = 0; i < c.size(); i++){
	n_occ[toInt(c[i])]--;
	updateElimHeap(var(c[i]));
      }
    
    detachClause(c);
    c.mark(1);
  }


  bool SimpSolver::strengthenClause(Clause& c, Lit l)
  {
    assert(decisionLevel() == 0);
    assert(c.mark() == 0);
    assert(!c.learnt());
    assert(find(watches[toInt(~c[0])], &c));
    assert(find(watches[toInt(~c[1])], &c));

    // FIX: this is too inefficient but would be nice to have (properly implemented)
    // if (!find(subsumption_queue, &c))
    subsumption_queue.insert(&c);

    // If l is watched, delete it from watcher list and watch a new literal
    if (c[0] == l || c[1] == l){
      Lit other = c[0] == l ? c[1] : c[0];
      if (c.size() == 2){
	removeClause(c);
	c.strengthen(l);
      }else{
	c.strengthen(l);
	remove(watches[toInt(~l)], &c);
	
	// Add a watch for the correct literal
	watches[toInt(~(c[1] == other ? c[0] : c[1]))].push(&c);
	
	// !! this version assumes that remove does not change the order !!
	//watches[toInt(~c[1])].push(&c);
	clauses_literals -= 1;
      }
    }
    else{
      c.strengthen(l);
      clauses_literals -= 1;
    }
    
    // if subsumption-indexing is active perform the necessary updates
    if (use_simplification){
      remove(occurs[var(l)], &c);
      n_occ[toInt(l)]--;
      updateElimHeap(var(l));
    }
    
    return c.size() == 1 ? enqueue(c[0]) && propagate() == NULL : true;
  }


  // Returns FALSE if clause is always satisfied ('out_clause' should not be used).
  bool SimpSolver::merge(const Clause& _ps, const Clause& _qs, Var v, vec<Lit>& out_clause)
  {
    merges++;
    out_clause.clear();
    
    bool  ps_smallest = _ps.size() < _qs.size();
    const Clause& ps =  ps_smallest ? _qs : _ps;
    const Clause& qs =  ps_smallest ? _ps : _qs;
    
    for (int i = 0; i < qs.size(); i++){
      if (var(qs[i]) != v){
	for (int j = 0; j < ps.size(); j++)
	  if (var(ps[j]) == var(qs[i]))
	    if (ps[j] == ~qs[i])
	      return false;
	    else
	      goto next;
	out_clause.push(qs[i]);
      }
    next:;
    }
    
    for (int i = 0; i < ps.size(); i++)
      if (var(ps[i]) != v)
	out_clause.push(ps[i]);
    
    return true;
  }


  // Returns FALSE if clause is always satisfied.
  bool SimpSolver::merge(const Clause& _ps, const Clause& _qs, Var v)
  {
    merges++;
    
    bool  ps_smallest = _ps.size() < _qs.size();
    const Clause& ps =  ps_smallest ? _qs : _ps;
    const Clause& qs =  ps_smallest ? _ps : _qs;
    const Lit* __ps = (const Lit*)ps;
    const Lit* __qs = (const Lit*)qs;

    for (int i = 0; i < qs.size(); i++){
      if (var(__qs[i]) != v){
	for (int j = 0; j < ps.size(); j++)
	  if (var(__ps[j]) == var(__qs[i]))
	    if (__ps[j] == ~__qs[i])
	      return false;
	    else
	      goto next;
      }
    next:;
    }
    
    return true;
  }


  void SimpSolver::gatherTouchedClauses()
  {
    //fprintf(stderr, "Gathering clauses for backwards subsumption\n");
    int ntouched = 0;
    for (int i = 0; i < touched.size(); i++)
      if (touched[i]){
	const vec<Clause*>& cs = getOccurs(i);
	ntouched++;
	for (int j = 0; j < cs.size(); j++)
	  if (cs[j]->mark() == 0){
	    subsumption_queue.insert(cs[j]);
	    cs[j]->mark(2);
	  }
	touched[i] = 0;
      }
    
    for (int i = 0; i < subsumption_queue.size(); i++)
      subsumption_queue[i]->mark(0);
  }
  

  bool SimpSolver::implied(const vec<Lit>& c)
  {
    assert(decisionLevel() == 0);
    
    trail_lim.push(trail.size());
    for (int i = 0; i < c.size(); i++)
      if (value(c[i]) == l_True){
	cancelUntil(0);
	return false;
      }else if (value(c[i]) != l_False){
	assert(value(c[i]) == l_Undef);
	uncheckedEnqueue(~c[i]);// Enqueue a literal. Assumes value of literal is undefined.
      }
    
    bool result = propagate() != NULL;
    cancelUntil(0);
    return result;
  }
  
  
  // Backward subsumption + backward subsumption resolution
  bool SimpSolver::backwardSubsumptionCheck(bool verbose)
  {
    
    int subsumed = 0;
    int deleted_literals = 0;
    assert(decisionLevel() == 0);
    
    while (subsumption_queue.size() > 0 || bwdsub_assigns < trail.size()){
      
      // Check top-level assignments by creating a dummy clause and placing it in the queue:
      if (subsumption_queue.size() == 0 && bwdsub_assigns < trail.size()){
	Lit l = trail[bwdsub_assigns++];
	(*bwdsub_tmpunit)[0] = l;
	bwdsub_tmpunit->calcAbstraction();
	assert(bwdsub_tmpunit->mark() == 0);
	subsumption_queue.insert(bwdsub_tmpunit); }
      
      Clause&  c = *subsumption_queue.peek(); subsumption_queue.pop();
      
      if (c.mark()) continue;
      
      assert(c.size() > 1 || value(c[0]) == l_True);    // Unit-clauses should have been propagated before this point.
      
      // Find best variable to scan:
      Var best = var(c[0]);
      for (int i = 1; i < c.size(); i++)
	if (occurs[var(c[i])].size() < occurs[best].size())
	  best = var(c[i]);

      // Search all candidates:
      vec<Clause*>& _cs = getOccurs(best);
      Clause**       cs = (Clause**)_cs;
      
      for (int j = 0; j < _cs.size(); j++)
	if (c.mark())
	  break;
	else if (!cs[j]->mark() && cs[j] != &c){
	  Lit l = c.subsumes(*cs[j]);
	  
	  if (l == lit_Undef)
	    subsumed++, removeClause(*cs[j]);
	  else if (l != lit_Error){
	    deleted_literals++;
	    
	    if (!strengthenClause(*cs[j], ~l))
	      return false;
	    
	    // Did current candidate get deleted from cs? Then check candidate at index j again:
	    if (var(l) == best)
	      j--;
	  }
	}
    }
    
    return true;
  }
  

  bool SimpSolver::asymm(Var v, Clause& c)
  {
    assert(decisionLevel() == 0);
    
    if (c.mark() || satisfied(c)) return true;
    
    trail_lim.push(trail.size());
    Lit l = lit_Undef;