/**Function********************************************************************
Synopsis [Performs the recursive steps of Cudd_bddBoleanDiff.]
Description [Performs the recursive steps of Cudd_bddBoleanDiff.
Returns the BDD obtained by XORing the cofactors of f with respect to
var if successful; NULL otherwise. Exploits the fact that dF/dx =
dF'/dx.]
SideEffects [None]
SeeAlso []
******************************************************************************/
DdNode *
cuddBddBooleanDiffRecur(
DdManager * manager,
DdNode * f,
DdNode * var)
{
DdNode *T, *E, *res, *res1, *res2;
statLine(manager);
if (cuddI(manager,f->index) > manager->perm[var->index]) {
/* f does not depend on var. */
return(Cudd_Not(DD_ONE(manager)));
}
/* From now on, f is non-constant. */
/* If the two indices are the same, so are their levels. */
if (f->index == var->index) {
res = cuddBddXorRecur(manager, cuddT(f), cuddE(f));
return(res);
}
/* From now on, cuddI(manager,f->index) < cuddI(manager,cube->index). */
/* Check the cache. */
res = cuddCacheLookup2(manager, cuddBddBooleanDiffRecur, f, var);
if (res != NULL) {
return(res);
}
/* Compute the cofactors of f. */
T = cuddT(f); E = cuddE(f);
res1 = cuddBddBooleanDiffRecur(manager, T, var);
if (res1 == NULL) return(NULL);
cuddRef(res1);
res2 = cuddBddBooleanDiffRecur(manager, Cudd_Regular(E), var);
if (res2 == NULL) {
Cudd_IterDerefBdd(manager, res1);
return(NULL);
}
cuddRef(res2);
/* ITE takes care of possible complementation of res1 and of the
** case in which res1 == res2. */
res = cuddBddIteRecur(manager, manager->vars[f->index], res1, res2);
if (res == NULL) {
Cudd_IterDerefBdd(manager, res1);
Cudd_IterDerefBdd(manager, res2);
return(NULL);
}
cuddDeref(res1);
cuddDeref(res2);
cuddCacheInsert2(manager, cuddBddBooleanDiffRecur, f, var, res);
return(res);
} /* end of cuddBddBooleanDiffRecur */
/**
@brief Computes the boolean difference of f with respect to x.
@details Computes the boolean difference of f with respect to the
variable with index x.
@return the %BDD of the boolean difference if successful; NULL
otherwise.
@sideeffect None
*/
DdNode *
Cudd_bddBooleanDiff(
DdManager * manager,
DdNode * f,
int x)
{
DdNode *res, *var;
/* If the variable is not currently in the manager, f cannot
** depend on it.
*/
if (x >= manager->size) return(Cudd_Not(DD_ONE(manager)));
var = manager->vars[x];
do {
manager->reordered = 0;
res = cuddBddBooleanDiffRecur(manager, Cudd_Regular(f), var);
} while (manager->reordered == 1);
if (manager->errorCode == CUDD_TIMEOUT_EXPIRED && manager->timeoutHandler) {
manager->timeoutHandler(manager, manager->tohArg);
}
return(res);
} /* end of Cudd_bddBooleanDiff */
/**Function********************************************************************
Synopsis [Computes the boolean difference of f with respect to x.]
Description [Computes the boolean difference of f with respect to the
variable with index x. Returns the BDD of the boolean difference if
successful; NULL otherwise.]
SideEffects [None]
SeeAlso []
******************************************************************************/
DdNode *
Cudd_bddBooleanDiff(
DdManager * manager,
DdNode * f,
int x)
{
DdNode *res, *var;
/* If the variable is not currently in the manager, f cannot
** depend on it.
*/
if (x >= manager->size) return(Cudd_Not(DD_ONE(manager)));
var = manager->vars[x];
do {
manager->reordered = 0;
res = cuddBddBooleanDiffRecur(manager, Cudd_Regular(f), var);
} while (manager->reordered == 1);
return(res);
} /* end of Cudd_bddBooleanDiff */
