Пример #1
0
LIST inf_URResolution(CLAUSE Clause, SHARED_INDEX Index, FLAGSTORE Flags,
		      PRECEDENCE Precedence)
/**************************************************************
  INPUT:   A clause, a shared index, a flag store and a precedence.
  RETURNS: The list of UR resolution resolvents.
  EFFECT:  The flag store and the precedence are needed to create
           the resolvents.
***************************************************************/
{
  LIST Result;

  if (clause_Length(Clause) != 1) {
    /* Clause isn't unit clause */
    Result = inf_NonUnitURResolution(Clause, -1, list_Nil(), subst_Nil(),
				     clause_MaxVar(Clause), Index, Flags,
				     Precedence);
  }
  else {
    /* Clause is unit clause, so search partner literals in non-unit clauses */
    LITERAL Lit, PLit;
    TERM    Atom;
    LIST    Partners, FoundMap;
    SYMBOL  MaxVar, PMaxVar;
    SUBST   LeftSubst, RightSubst;
    CLAUSE  PClause;
    int     PLitInd;
    BOOL    Swapped;

    Result   = list_Nil();
    Lit      = clause_GetLiteral(Clause, clause_FirstLitIndex());
    Atom     = term_Copy(clause_LiteralAtom(Lit));
    Swapped  = FALSE;

    /* The following 'endless' loop runs twice for equality literals */
    /* and only once for other literals.                             */
    while (TRUE) {
      /* Get complementary literals from non-unit clauses */
      Partners = inf_GetURPartnerLits(Atom, Lit, FALSE, Index);
      
      for ( ; !list_Empty(Partners); Partners = list_Pop(Partners)) {
	PLit     = list_Car(Partners);
	PLitInd  = clause_LiteralGetIndex(PLit);
	PClause  = clause_LiteralOwningClause(PLit); /* non-unit clause */
	
	PMaxVar   = clause_MaxVar(PClause);
	term_StartMaxRenaming(PMaxVar);
	term_Rename(Atom);              /* Rename atom from unit clause */
	MaxVar = term_MaxVar(Atom); 
	if (symbol_GreaterVariable(PMaxVar, MaxVar))
	  MaxVar = PMaxVar;
	
	/* Get the substitution */
	cont_Check();
	unify_UnifyNoOC(cont_LeftContext(), clause_LiteralAtom(PLit),
			cont_RightContext(), Atom);
	subst_ExtractUnifier(cont_LeftContext(), &LeftSubst,
			     cont_RightContext(), &RightSubst);
	cont_Reset();
	/* We don't need the substitution for the unit clause */
	subst_Delete(RightSubst);
	
	FoundMap = list_List(list_PairCreate(PLit, Lit));
	
	Result = list_Nconc(inf_NonUnitURResolution(PClause, PLitInd, FoundMap,
						    LeftSubst, MaxVar, Index,
						    Flags, Precedence),
			    Result);
	
	list_DeletePairList(FoundMap);
	subst_Delete(LeftSubst);
      }
      /* loop control */
      if (!fol_IsEquality(Atom) || Swapped)
	break;
      else {
	term_EqualitySwap(Atom);
	Swapped = TRUE;
      }
    }  /* end of endless loop */
    term_Delete(Atom);
  }
  return Result;
}
Пример #2
0
static CLAUSE red_SearchTerminator(NAT n, LIST RestLits, LIST FoundMap,
				   SUBST Subst, SYMBOL GlobalMaxVar,
				   LIST IndexList, FLAGSTORE Flags,
				   PRECEDENCE Precedence)
/**************************************************************
  INPUT:   A natural number, a list of literals, a list of pairs,
           a substitution, the maximum variable occurring in all
	   involved clauses, a list of SHARED_INDEXes, a flag store
	   and a precedence.
  RETURNS: An empty clause, if a terminator situation was found,
           NULL otherwise.
  EFFECT:  This recursive function implements the search for
           a terminator situation with at most <n> non-unit clauses.
	   <RestLits> is the lists of literals actually missing
	   a complementary partner literal.
	   <FoundMap> is a list of pairs (l1,l2), where l1 and l2
	   are complementary, unifiable literals.
	   <Subst> is the common substitution of all those pairs.
	   <GlobalMaxVar> is the maximum variable from all
	   involved clauses.
	   To enable the search all involved clauses are made
	   variable-disjoint.
	   At the moment the function stops, if ANY terminator
	   situation occurred. This might not be desirable
	   if splitting is enabled, since there might be other
	   terminator situations resulting in an empty clause
	   of lower split level.
	   The flag store and the precedence are needed to create
	   the new clause.
***************************************************************/
{
  if (list_Empty(RestLits)) {
    /* We found a terminator situation, so stop the recursion */
    return red_CreateTerminatorEmptyClause(FoundMap, Flags, Precedence);
  } else {
    CLAUSE  Result, PClauseCopy;
    LITERAL Lit, PLit;
    SYMBOL  NewMaxVar;
    SUBST   NewSubst, RightSubst;
    TERM    AtomCopy;
    LIST    ClashList, ToDoList;
    BOOL    Swapped;
    NAT     Limit;
    int     PLitInd;

    Swapped   = FALSE;
    Result    = clause_Null();
    clause_MoveBestLiteralToFront(RestLits, Subst, GlobalMaxVar,
				  red_TerminatorLitIsBetter);
    Lit       = list_Car(RestLits);
    RestLits  = list_Cdr(RestLits);
    AtomCopy  = subst_Apply(Subst, term_Copy(clause_LiteralAtom(Lit)));

    /* The following 'endless' loop runs twice for equality literals */
    /* and only once for other literals.                             */
    while (TRUE) {
      ClashList = red_GetTerminatorPartnerLits(AtomCopy, Lit, n==0, IndexList);
      for (; !list_Empty(ClashList) && Result==NULL;
	   ClashList = list_Pop(ClashList)) {
	PLit        = list_Car(ClashList);
	PLitInd     = clause_LiteralGetIndex(PLit);
	PClauseCopy = clause_Copy(clause_LiteralOwningClause(PLit));
	Limit       = clause_Length(PClauseCopy) == 1 ? n : n-1;
	
	clause_RenameVarsBiggerThan(PClauseCopy, GlobalMaxVar);
	
	PLit        = clause_GetLiteral(PClauseCopy, PLitInd);
	FoundMap    = list_Cons(list_PairCreate(Lit, PLit), FoundMap);
	ToDoList    = clause_GetLiteralListExcept(PClauseCopy, PLitInd);
	ToDoList    = list_Nconc(ToDoList, list_Copy(RestLits));
	
	NewMaxVar   = clause_SearchMaxVar(PClauseCopy);
	if (symbol_GreaterVariable(GlobalMaxVar, NewMaxVar))
	  NewMaxVar = GlobalMaxVar;
	
	cont_Check();
	if (!unify_UnifyNoOC(cont_LeftContext(), AtomCopy,
			     cont_RightContext(), clause_LiteralAtom(PLit))) {
	  misc_StartErrorReport();
	  misc_ErrorReport("\n In red_SearchTerminator: Unification failed.");
	  misc_FinishErrorReport();
	}
	subst_ExtractUnifier(cont_LeftContext(), &NewSubst,
			     cont_RightContext(), &RightSubst);
	cont_Reset();
	
	/* The domains of both substitutions are disjoint */
	/* so we do just a simple union operation.        */
	NewSubst = subst_NUnion(NewSubst, RightSubst);
	RightSubst = NewSubst;
	NewSubst  = subst_Compose(NewSubst, subst_Copy(Subst));
	subst_Delete(RightSubst);
	
	Result = red_SearchTerminator(Limit, ToDoList, FoundMap, NewSubst,
				      NewMaxVar, IndexList, Flags, Precedence);
	
	clause_Delete(PClauseCopy);
	subst_Delete(NewSubst);
	list_Delete(ToDoList);
	list_PairFree(list_Car(FoundMap));
	FoundMap = list_Pop(FoundMap);
      }
      /* loop control */
      if (!fol_IsEquality(AtomCopy) || Swapped || Result!=NULL)
	break;
      else {
	list_Delete(ClashList);
	term_EqualitySwap(AtomCopy);
	Swapped = TRUE;
      }
    }
    /* cleanup */
    term_Delete(AtomCopy);
    /* <ClashList> may be non-empty since the loop stops */
    /* if a terminator was found.                       */
    list_Delete(ClashList);
    
    return Result;
  }
}
Пример #3
0
static LIST inf_SearchURResolvents(CLAUSE Clause, int i, LIST FoundMap,
				   LIST RestLits, SUBST Subst,
				   SYMBOL GlobalMaxVar, SHARED_INDEX Index,
				   FLAGSTORE Flags, PRECEDENCE Precedence)
/**************************************************************
  INPUT:   A non-unit clause, a literal index from <Clause>.
           <FoundMap> is a list of pairs (l1,l2) of unifiable literals,
	   where l1 is from <Clause> and l2 is from a unit clause.
	   <RestLits> is a list of literals from <Clause> where
	   we haven't found unifiable literals from unit clauses
	   so far.
	   <Subst> is the overall substitution for <Clause>
	   (not for the unit-clauses!).
	   <GlobalMaxVar> is the maximal variable encountered so far.
	   <Index> is used to search unifiable literals.
	   The flag store and the precedence are needed to create
	   the new clauses.
  RETURNS: A list of UR resolution resolvents.
***************************************************************/
{
  if (list_Empty(RestLits)) {
    /* Stop the recursion */
    return list_List(inf_CreateURUnitResolvent(Clause, i, Subst, FoundMap,
					       Flags, Precedence));
  } else {
    LITERAL Lit, PLit;
    SYMBOL  NewMaxVar;
    SUBST   NewSubst, RightSubst;
    TERM    AtomCopy, PAtom;
    LIST    Result, Partners;
    BOOL    Swapped;

    Result   = list_Nil();
    Swapped  = FALSE;
    /* Choose the unmatched literal with the most symbols */
    RestLits = clause_MoveBestLiteralToFront(list_Copy(RestLits), Subst,
					     GlobalMaxVar,
					     clause_HyperLiteralIsBetter);
    Lit      = list_Car(RestLits);
    RestLits = list_Pop(RestLits);
    AtomCopy = subst_Apply(Subst, term_Copy(clause_LiteralAtom(Lit)));

    /* The following 'endless' loop runs twice for equality literals */
    /* and only once for other literals.                             */
    while (TRUE) {
      Partners = inf_GetURPartnerLits(AtomCopy, Lit, TRUE, Index);
      for ( ; !list_Empty(Partners); Partners = list_Pop(Partners)) {
	PLit    = list_Car(Partners);

	/* Rename the atom */
	PAtom   = term_Copy(clause_LiteralAtom(PLit));
	term_StartMaxRenaming(GlobalMaxVar);
	term_Rename(PAtom);
	/* Get the new global maximal variable */
	NewMaxVar = term_MaxVar(PAtom);
	if (symbol_GreaterVariable(GlobalMaxVar, NewMaxVar))
	  NewMaxVar = GlobalMaxVar;
	
	/* Get the substitution */
	cont_Check();
	if (!unify_UnifyNoOC(cont_LeftContext(), AtomCopy,
			     cont_RightContext(), PAtom)) {
	  misc_StartErrorReport();
	  misc_ErrorReport("\n In inf_SearchURResolvents: Unification failed.");
	  misc_FinishErrorReport();
	}
	subst_ExtractUnifier(cont_LeftContext(), &NewSubst,
			     cont_RightContext(), &RightSubst);
	cont_Reset();
	subst_Delete(RightSubst);  /* Forget substitution for unit clause */
	term_Delete(PAtom);  /* Was just needed to get the substitution */

	/* Build the composition of the substitutions */
	RightSubst = NewSubst;
	NewSubst = subst_Compose(NewSubst, subst_Copy(Subst));
	subst_Delete(RightSubst);

	FoundMap    = list_Cons(list_PairCreate(Lit, PLit), FoundMap);
	
	Result = list_Nconc(inf_SearchURResolvents(Clause,i,FoundMap,RestLits,
						   NewSubst,NewMaxVar,Index,
						   Flags, Precedence),
			    Result);
	
	list_PairFree(list_Car(FoundMap));
	FoundMap = list_Pop(FoundMap);
	subst_Delete(NewSubst);
      }
      /* loop control */
      if (!fol_IsEquality(AtomCopy) || Swapped)
	break;
      else {
	term_EqualitySwap(AtomCopy);
	Swapped = TRUE;
      }
    }
    /* cleanup */
    term_Delete(AtomCopy);
    list_Delete(RestLits);
    
    return Result;
  }
}