/**CFile***********************************************************************

  FileName    [cuddAddFind.c]

  PackageName [cudd]

  Synopsis    [Functions to find maximum and minimum in an ADD and to
  extract the i-th bit.]

  Description [External procedures included in this module:
		<ul>
		<li> Cudd_addFindMax()
		<li> Cudd_addFindMin()
		<li> Cudd_addIthBit()
		</ul>
	       Static functions included in this module:
		<ul>
		<li> addDoIthBit()
		</ul>]

  Author      [Fabio Somenzi]

  Copyright   [This file was created at the University of Colorado at
  Boulder.  The University of Colorado at Boulder makes no warranty
  about the suitability of this software for any purpose.  It is
  presented on an AS IS basis.]

******************************************************************************/

#include "util.h"
#include "cuddInt.h"

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/* Constant declarations                                                     */
/*---------------------------------------------------------------------------*/


/*---------------------------------------------------------------------------*/
/* Stucture declarations                                                     */
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/*---------------------------------------------------------------------------*/
/* Type declarations                                                         */
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/*---------------------------------------------------------------------------*/
/* Variable declarations                                                     */
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#ifndef lint
static char rcsid[] DD_UNUSED = "$Id: cuddAddFind.c,v 1.1 2002/09/17 21:58:46 dlm Exp $";
#endif


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/* Macro declarations                                                        */
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/**AutomaticStart*************************************************************/

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/* Static function prototypes                                                */
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static DdNode * addDoIthBit ARGS((DdManager *dd, DdNode *f, DdNode *index));

/**AutomaticEnd***************************************************************/


/*---------------------------------------------------------------------------*/
/* Definition of exported functions                                          */
/*---------------------------------------------------------------------------*/

/**Function********************************************************************

  Synopsis    [Finds the maximum discriminant of f.]

  Description [Returns a pointer to a constant ADD.]

  SideEffects [None]

******************************************************************************/
DdNode *
Cudd_addFindMax(
  DdManager * dd,
  DdNode * f)
{
    DdNode *t, *e, *res;

    statLine(dd);
    if (cuddIsConstant(f)) {
	return(f);
    }

    res = cuddCacheLookup1(dd,Cudd_addFindMax,f);
    if (res != NULL) {
	return(res);
    }

    t  = Cudd_addFindMax(dd,cuddT(f));
    if (t == DD_PLUS_INFINITY(dd)) return(t);

    e  = Cudd_addFindMax(dd,cuddE(f));

    res = (cuddV(t) >= cuddV(e)) ? t : e;

    cuddCacheInsert1(dd,Cudd_addFindMax,f,res);

    return(res);

} /* end of Cudd_addFindMax */


/**Function********************************************************************

  Synopsis    [Finds the minimum discriminant of f.]

  Description [Returns a pointer to a constant ADD.]

  SideEffects [None]

******************************************************************************/
DdNode *
Cudd_addFindMin(
  DdManager * dd,
  DdNode * f)
{
    DdNode *t, *e, *res;

    statLine(dd);
    if (cuddIsConstant(f)) {
	return(f);
    }

    res = cuddCacheLookup1(dd,Cudd_addFindMin,f);
    if (res != NULL) {
	return(res);
    }

    t  = Cudd_addFindMin(dd,cuddT(f));
    if (t == DD_MINUS_INFINITY(dd)) return(t);

    e  = Cudd_addFindMin(dd,cuddE(f));

    res = (cuddV(t) <= cuddV(e)) ? t : e;

    cuddCacheInsert1(dd,Cudd_addFindMin,f,res);

    return(res);

} /* end of Cudd_addFindMin */


/**Function********************************************************************

  Synopsis    [Extracts the i-th bit from an ADD.]

  Description [Produces an ADD from another ADD by replacing all
  discriminants whose i-th bit is equal to 1 with 1, and all other
  discriminants with 0. The i-th bit refers to the integer
  representation of the leaf value. If the value is has a fractional
  part, it is ignored. Repeated calls to this procedure allow one to
  transform an integer-valued ADD into an array of ADDs, one for each
  bit of the leaf values. Returns a pointer to the resulting ADD if
  successful; NULL otherwise.]

  SideEffects [None]

  SeeAlso     [Cudd_addBddIthBit]

******************************************************************************/
DdNode *
Cudd_addIthBit(
  DdManager * dd,
  DdNode * f,
  int  bit)
{
    DdNode *res;
    DdNode *index;
    
    /* Use a constant node to remember the bit, so that we can use the
    ** global cache.
    */
    index = cuddUniqueConst(dd,(CUDD_VALUE_TYPE) bit);
    if (index == NULL) return(NULL);
    cuddRef(index);

    do {
	dd->reordered = 0;
	res = addDoIthBit(dd, f, index);
    } while (dd->reordered == 1);

    if (res == NULL) {
	Cudd_RecursiveDeref(dd, index);
	return(NULL);
    }
    cuddRef(res);
    Cudd_RecursiveDeref(dd, index);
    cuddDeref(res);
    return(res);

} /* end of Cudd_addIthBit */


/*---------------------------------------------------------------------------*/
/* Definition of internal functions                                          */
/*---------------------------------------------------------------------------*/


/*---------------------------------------------------------------------------*/
/* Definition of static functions                                            */
/*---------------------------------------------------------------------------*/


/**Function********************************************************************

  Synopsis    [Performs the recursive step for Cudd_addIthBit.]

  Description [Performs the recursive step for Cudd_addIthBit.
  Returns a pointer to the BDD if successful; NULL otherwise.]

  SideEffects [None]

  SeeAlso     []

******************************************************************************/
static DdNode *
addDoIthBit(
  DdManager * dd,
  DdNode * f,
  DdNode * index)
{
    DdNode *res, *T, *E;
    DdNode *fv, *fvn;
    int mask, value;
    int v;

    statLine(dd);
    /* Check terminal case. */
    if (cuddIsConstant(f)) {
	mask = 1 << ((int) cuddV(index));
	value = (int) cuddV(f);
	return((value & mask) == 0 ? DD_ZERO(dd) : DD_ONE(dd));
    }

    /* Check cache. */
    res = cuddCacheLookup2(dd,addDoIthBit,f,index);
    if (res != NULL) return(res);

    /* Recursive step. */
    v = f->index;
    fv = cuddT(f); fvn = cuddE(f);

    T = addDoIthBit(dd,fv,index);
    if (T == NULL) return(NULL);
    cuddRef(T);

    E = addDoIthBit(dd,fvn,index);
    if (E == NULL) {
	Cudd_RecursiveDeref(dd, T);
	return(NULL);
    }
    cuddRef(E);

    res = (T == E) ? T : cuddUniqueInter(dd,v,T,E);
    if (res == NULL) {
	Cudd_RecursiveDeref(dd, T);
	Cudd_RecursiveDeref(dd, E);
	return(NULL);
    }
    cuddDeref(T);
    cuddDeref(E);

    /* Store result. */
    cuddCacheInsert2(dd,addDoIthBit,f,index,res);

    return(res);

} /* end of addDoIthBit */

