static void cc_InitData(CLAUSE clause)
/***************************************************************
INPUT: the clause to investigate
EFFECT: pushes clause's atoms and their subterms on the
pending stack, initializes each predecessor list with
the list containing only a term's father, and unions
the equivalence classes of the terms of the same
antecedent equation
***************************************************************/
{
int last, actno, i, ld;
TERM atom;
RAS cdr, size;
cc_SetCars(ras_InitWithSize(cc_GetCars(), cc_RASSTDSIZE));
cc_SetPending(ras_InitWithSize(cc_GetPending(), cc_RASSTDSIZE));
ras_FastPush(cc_GetCars(), term_Null()); /* "true" has no predecessors */
actno = 1;
last = clause_LastLitIndex(clause);
for (i = clause_FirstLitIndex(); i <= last; i++) {
atom = clause_GetLiteralAtom(clause, i);
if (fol_IsEquality(atom)) {
actno = cc_Number(actno, term_FirstArgument(atom), term_Null());
actno = cc_Number(actno, term_SecondArgument(atom), term_Null());
}
else
actno = cc_Number(actno, atom, term_Null());
}
cc_SetPartition(part_Init(cc_GetPartition(), actno));
cc_SetTable(table_Init(cc_GetTable(), symbol_ActIndex() - 1,
clause_MaxVar(clause), actno - 1));
cdr = ras_InitWithSize(cc_GetCdrs(), actno);
size = ras_InitWithSize(cc_GetSizes(), actno);
for (i = 0; i < actno; i++) {
ras_FastPush(cdr, (POINTER) i); /* form a cycle */
ras_FastPush(size, (POINTER) (cc_GetCar(i) == term_Null()? 0 : 1));
}
cc_SetCdrs(cdr);
cc_SetSizes(size);
/* compute ceil(ld(actno)) avoiding mathbib-logarithm's rounding errors: */
for (ld = 0, i = actno - 1; i > 0; i >>= 1)
ld++;
cc_SetCombine(ras_InitWithSize(cc_GetCombine(), actno * ld + 1));
/* for every antecedent equation union equivalence classes of its terms */
/* (a non-equational atom is represented as the equation atom = "true"): */
last = clause_LastAntecedentLitIndex(clause);
for (i = clause_FirstLitIndex(); i <= last; i++) {
atom = clause_GetLiteralAtom(clause, i);
if (fol_IsEquality(atom))
cc_Union(term_Size(term_FirstArgument(atom)), /* clause not shared, therefore */
term_Size(term_SecondArgument(atom))); /* here no cc_Find needed */
else
cc_Union(term_Size(atom), part_Find(cc_GetPartition(), cc_NOOFTRUE));
}
}
static LIST inf_NonUnitURResolution(CLAUSE Clause, int SpecialLitIndex,
LIST FoundMap, 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.
At this point the list has at most one element.
<Subst> is the substitution for <Clause>.
<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: The list of UR resolution resolvents.
EFFECT: If inf_URResolution was called with a unit clause,
<SpecialLitIndex> is the index of a literal from a non-unit
clause, that is unifiable with the unit clause's literal,
otherwise it is set to -1.
***************************************************************/
{
LIST Result, RestLits;
int i, last;
Result = list_Nil();
RestLits = clause_GetLiteralListExcept(Clause, SpecialLitIndex);
last = clause_LastLitIndex(Clause);
for (i = clause_FirstLitIndex(); i <= last; i++) {
/* <i> is the index of the literal that remains in the resolvent */
if (i != SpecialLitIndex) {
RestLits = list_PointerDeleteOneElement(RestLits,
clause_GetLiteral(Clause,i));
Result = list_Nconc(inf_SearchURResolvents(Clause, i, FoundMap, RestLits,
Subst, GlobalMaxVar, Index,
Flags, Precedence),
Result);
RestLits = list_Cons(clause_GetLiteral(Clause, i), RestLits);
}
}
list_Delete(RestLits);
return Result;
}
static LIST ana_CalculatePredicatePrecedence(LIST Predicates, LIST Clauses)
/**************************************************************
INPUT: A list of predicates and a list of clauses.
RETURNS: A list of predicate symbols, which should be used
for setting the symbol precedence. The list is sorted
in descending order, that means predicates with highest
precedence come first.
EFFECT: Analyze the clause list to build a directed graph G where
the predicates are vertices. There's an edge (P,Q) in
G iff a clause exists where P is a negative literal
and Q is a positive literal and P != Q. Apply DFS to
find the strongly connected components of this graph.
The <Predicates> list is deleted.
CAUTION: The predicate list must contain ALL predicates
occurring in the clause list!
***************************************************************/
{
GRAPH graph;
LIST result, scan;
int i, j;
NAT count;
SYMBOL s;
/* clause_ListPrint(Clauses); DBG */
if (list_Empty(Predicates)) {
return Predicates;
}
graph = graph_Create();
/* First create the nodes: one node for every predicate symbol. */
for ( ; !list_Empty(Predicates); Predicates = list_Pop(Predicates))
graph_AddNode(graph, symbol_Index((SYMBOL)list_Car(Predicates)));
/* Now scan the clause clause list to create the edges */
/* An edge (P,Q) means P is smaller than Q */
for (scan = Clauses; !list_Empty(scan); scan = list_Cdr(scan)) {
CLAUSE c = list_Car(scan);
for (i = clause_FirstLitIndex(); i < clause_FirstSuccedentLitIndex(c); i++) {
SYMBOL negPred = term_TopSymbol(clause_GetLiteralAtom(c, i));
if (!symbol_Equal(negPred, fol_Equality())) { /* negative predicate */
for (j = clause_FirstSuccedentLitIndex(c); j < clause_Length(c); j++) {
SYMBOL posPred = term_TopSymbol(clause_GetLiteralAtom(c, j));
if (!symbol_Equal(posPred, fol_Equality()) && /* positive predicate */
negPred != posPred) { /* No self loops! */
graph_AddEdge(graph_GetNode(graph, symbol_Index(negPred)),
graph_GetNode(graph, symbol_Index(posPred)));
}
}
}
}
}
/* graph_Print(graph); fflush(stdout); DBG */
/* Calculate the strongly connected components of the graph */
count = graph_StronglyConnectedComponents(graph);
/* Now create the precedence list by scanning the nodes. */
/* If there's a link between two strongly connected components */
/* c1 and c2 then component_num(c1) > component_num(c2), so the */
/* following code creates a valid precedence list in descending */
/* order. */
result = list_Nil();
for (i = count - 1; i >= 0; i--) {
for (scan = graph_Nodes(graph); !list_Empty(scan); scan = list_Cdr(scan)) {
GRAPHNODE n = list_Car(scan);
if (graph_NodeCompNum(n) == i) {
/* The symbol represented by the node <<n> belongs to component <i> */
s = symbol_GetSigSymbol(graph_NodeNumber(n));
result = list_Cons((POINTER)s, result);
}
}
}
/* putchar('\n');
for (scan = result; !list_Empty(scan); scan = list_Cdr(scan)) {
s = (SYMBOL) list_Car(scan);
symbol_Print(s);
putchar(' ');
}
putchar('\n'); fflush(stdout); DBG */
graph_Delete(graph);
return result;
}
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;
}
