zchaff_dbase.cpp

命题逻辑的求解器,2004年SAT竞赛第一名的求解器

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#include <iostream>
#include <vector>
#include <set>

using namespace std;

#include "zchaff_dbase.h"

CDatabase::CDatabase(void) {
  _stats.mem_used_up                 = false;
  _stats.init_num_clauses            = 0;
  _stats.init_num_literals           = 0;
  _stats.num_added_clauses           = 0;
  _stats.num_added_literals          = 0;
  _stats.num_deleted_clauses         = 0;
  _stats.num_del_orig_cls            = 0;
  _stats.num_deleted_literals        = 0;
  _stats.num_enlarge                 = 0;
  _stats.num_compact                 = 0;
  _lit_pool_start = (CLitPoolElement *) malloc(sizeof(CLitPoolElement) *
                                               STARTUP_LIT_POOL_SIZE);
  _lit_pool_finish = _lit_pool_start;
  _lit_pool_end_storage = _lit_pool_start + STARTUP_LIT_POOL_SIZE;
  lit_pool_push_back(0);  // set the first element as a dummy element
  _params.mem_limit = 1024 * 1024 * 1024;  // that's 1 G
  variables()->resize(1);                  // var_id == 0 is never used.
  _allocated_gid                    = 0;
}

CDatabase::~CDatabase(void) {
  free(_lit_pool_start);
}

unsigned CDatabase::estimate_mem_usage(void) {
  unsigned mem_lit_pool = sizeof(CLitPoolElement) * (lit_pool_size() +
                                                     lit_pool_free_space());
  unsigned mem_vars = sizeof(CVariable) * variables()->capacity();
  unsigned mem_cls = sizeof(CClause) * clauses()->capacity();
  unsigned mem_cls_queue = sizeof(int) * _unused_clause_idx.size();
  unsigned mem_watched = 2 * num_clauses() * sizeof(CLitPoolElement *);
  unsigned mem_lit_clauses = 0;
#ifdef KEEP_LIT_CLAUSES
  mem_lit_clauses = num_literals() * sizeof(ClauseIdx);
#endif
  return (mem_lit_pool + mem_vars + mem_cls +
          mem_cls_queue + mem_watched + mem_lit_clauses);
}

unsigned CDatabase::mem_usage(void) {
  int mem_lit_pool = (lit_pool_size() + lit_pool_free_space()) *
                     sizeof(CLitPoolElement);
  int mem_vars = sizeof(CVariable) * variables()->capacity();
  int mem_cls = sizeof(CClause) * clauses()->capacity();
  int mem_cls_queue = sizeof(int) * _unused_clause_idx.size();
  int mem_watched = 0, mem_lit_clauses = 0;
  for (unsigned i = 0, sz = variables()->size(); i < sz ;  ++i) {
    CVariable & v = variable(i);
    mem_watched        += v.watched(0).capacity() + v.watched(1).capacity();
#ifdef KEEP_LIT_CLAUSES
    mem_lit_clauses += v.lit_clause(0).capacity() + v.lit_clause(1).capacity();
#endif
  }
  mem_watched *= sizeof(CLitPoolElement*);
  mem_lit_clauses *= sizeof(ClauseIdx);
  return (mem_lit_pool + mem_vars + mem_cls +
          mem_cls_queue + mem_watched + mem_lit_clauses);
}

int CDatabase::alloc_gid(void) {
  for (unsigned i = 1; i <= WORD_WIDTH; ++i) {
    if (is_gid_allocated(i) == false) {
      _allocated_gid |= (1 << (i-1));
      return i;
    }
  }
  warning(_POSITION_, "Not enough GID");
  return VOLATILE_GID;
}

void CDatabase::free_gid(int gid) {
  assert(gid > 0 && "Can't free volatile or permanent group");
  assert(gid <= WORD_WIDTH && "gid > WORD_WIDTH?");
  if (!is_gid_allocated(gid)) {
    fatal(_POSITION_, "Can't free unallocated GID");
  }
  _allocated_gid &= (~(1<< (gid-1)));
}

bool CDatabase::is_gid_allocated(int gid) {
  if (gid == VOLATILE_GID || gid == PERMANENT_GID)
    return true;
  assert(gid <= WORD_WIDTH && gid > 0);
  if (_allocated_gid & (1 << (gid -1)))
    return true;
  return false;
}

int CDatabase::merge_clause_group(int g2, int g1) {
  assert(g1 >0 && g2> 0 && "Can't merge with permanent or volatile group");
  assert(g1 != g2);
  assert(is_gid_allocated(g1) && is_gid_allocated(g2));
  for (unsigned i = 0, sz = clauses()->size(); i < sz; ++i) {
    if (clause(i).status() != DELETED_CL) {
      if (clause(i).gid(g1) == true) {
        clause(i).clear_gid(g1);
        clause(i).set_gid(g2);
      }
    }
  }
  free_gid(g1);
  return g2;
}

void CDatabase::mark_clause_deleted(CClause & cl) {
  ++_stats.num_deleted_clauses;
  _stats.num_deleted_literals += cl.num_lits();
  CLAUSE_STATUS status = cl.status();
  if (status == ORIGINAL_CL)
     _stats.num_del_orig_cls++;
  cl.set_status(DELETED_CL);
  for (unsigned i = 0; i < cl.num_lits(); ++i) {
    CLitPoolElement & l = cl.literal(i);
    --variable(l.var_index()).lits_count(l.var_sign());
    l.val() = 0;
  }
  _unused_clause_idx.insert(&cl - &(*clauses()->begin()));
}

bool CDatabase::is_conflicting(ClauseIdx cl) {
  CLitPoolElement * lits = clause(cl).literals();
  for (int i = 0, sz= clause(cl).num_lits(); i < sz;  ++i) {
    if (literal_value(lits[i]) != 0)
      return false;
  }
  return true;
}

bool CDatabase::is_satisfied(ClauseIdx cl) {
  CLitPoolElement * lits = clause(cl).literals();
  for (int i = 0, sz = clause(cl).num_lits(); i < sz; ++i) {
    if (literal_value(lits[i]) == 1)
      return true;
  }
  return false;
}

bool CDatabase::is_unit(ClauseIdx cl) {
  int num_unassigned = 0;
  CLitPoolElement * lits = clause(cl).literals();
  for (unsigned i = 0, sz= clause(cl).num_lits(); i < sz;  ++i) {
    int value = literal_value(lits[i]);
    if (value == 1)
      return false;
    else if (value != 0)
      ++num_unassigned;
  }
  return num_unassigned == 1;
}

int CDatabase::find_unit_literal(ClauseIdx cl) {
  // will return 0 if not unit
  int unit_lit = 0;
  for (int i = 0, sz = clause(cl).num_lits(); i < sz;  ++i) {
    int value = literal_value(clause(cl).literal(i));
    if (value == 1)
      return 0;
    else if (value != 0) {
      if (unit_lit == 0)
        unit_lit = clause(cl).literals()[i].s_var();
      else
        return 0;
    }
  }
  return unit_lit;
}

inline CLitPoolElement * CDatabase::lit_pool_begin(void) {
  return _lit_pool_start;
}

inline CLitPoolElement * CDatabase::lit_pool_end(void) {
  return _lit_pool_finish;
}

inline void CDatabase::lit_pool_incr_size(int size) {
  _lit_pool_finish += size;
  assert(_lit_pool_finish <= _lit_pool_end_storage);
}

inline void CDatabase::lit_pool_push_back(int value) {
  assert(_lit_pool_finish <= _lit_pool_end_storage);
  _lit_pool_finish->val() = value;
  ++_lit_pool_finish;
}

inline int CDatabase::lit_pool_size(void) {
  return _lit_pool_finish - _lit_pool_start;
}

inline int CDatabase::lit_pool_free_space(void) {
  return _lit_pool_end_storage - _lit_pool_finish;
}

inline double CDatabase::lit_pool_utilization(void) {