cuddRef.c

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

  FileName    [cuddRef.c]

  PackageName [cudd]

  Synopsis    [Functions that manipulate the reference counts.]

  Description [External procedures included in this module:
                    <ul>
                    <li> Cudd_Ref()
                    <li> Cudd_RecursiveDeref()
                    <li> Cudd_IterDerefBdd()
                    <li> Cudd_DelayedDerefBdd()
                    <li> Cudd_RecursiveDerefZdd()
                    <li> Cudd_Deref()
                    <li> Cudd_CheckZeroRef()
                    </ul>
               Internal procedures included in this module:
                    <ul>
                    <li> cuddReclaim()
                    <li> cuddReclaimZdd()
                    <li> cuddClearDeathRow()
                    <li> cuddShrinkDeathRow()
                    <li> cuddIsInDeathRow()
                    <li> cuddTimesInDeathRow()
                    </ul>
              ]

  SeeAlso     []

  Author      [Fabio Somenzi]

  Copyright   [Copyright (c) 1995-2004, Regents of the University of Colorado

  All rights reserved.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions
  are met:

  Redistributions of source code must retain the above copyright
  notice, this list of conditions and the following disclaimer.

  Redistributions in binary form must reproduce the above copyright
  notice, this list of conditions and the following disclaimer in the
  documentation and/or other materials provided with the distribution.

  Neither the name of the University of Colorado nor the names of its
  contributors may be used to endorse or promote products derived from
  this software without specific prior written permission.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  POSSIBILITY OF SUCH DAMAGE.]

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

#include "misc/util/util_hack.h"
#include "cuddInt.h"

ABC_NAMESPACE_IMPL_START



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/* Variable declarations                                                     */
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#ifndef lint
static char rcsid[] DD_UNUSED = "$Id: cuddRef.c,v 1.28 2004/08/13 18:04:50 fabio Exp $";
#endif

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

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/* Static function prototypes                                                */
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/* Definition of exported functions                                          */
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/**Function********************************************************************

  Synopsis [Increases the reference count of a node, if it is not
  saturated.]

  Description []

  SideEffects [None]

  SeeAlso     [Cudd_RecursiveDeref Cudd_Deref]

******************************************************************************/
void
Cudd_Ref(
  DdNode * n)
{

    n = Cudd_Regular(n);

    cuddSatInc(n->ref);

} /* end of Cudd_Ref */


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

  Synopsis    [Decreases the reference count of node n.]

  Description [Decreases the reference count of node n. If n dies,
  recursively decreases the reference counts of its children.  It is
  used to dispose of a DD that is no longer needed.]

  SideEffects [None]

  SeeAlso     [Cudd_Deref Cudd_Ref Cudd_RecursiveDerefZdd]

******************************************************************************/
void
Cudd_RecursiveDeref(
  DdManager * table,
  DdNode * n)
{
    DdNode *N;
    int ord;
    DdNodePtr *stack = table->stack;
    int SP = 1;

    unsigned int live = table->keys - table->dead;
    if (live > table->peakLiveNodes) {
        table->peakLiveNodes = live;
    }

    N = Cudd_Regular(n);

    do {
#ifdef DD_DEBUG
        assert(N->ref != 0);
#endif

        if (N->ref == 1) {
            N->ref = 0;
            table->dead++;
#ifdef DD_STATS
            table->nodesDropped++;
#endif
            if (cuddIsConstant(N)) {
                table->constants.dead++;
                N = stack[--SP];
            } else {
                ord = table->perm[N->index];
                stack[SP++] = Cudd_Regular(cuddE(N));
                table->subtables[ord].dead++;
                N = cuddT(N);
            }
        } else {
            cuddSatDec(N->ref);
            N = stack[--SP];
        }
    } while (SP != 0);

} /* end of Cudd_RecursiveDeref */


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

  Synopsis    [Decreases the reference count of BDD node n.]

  Description [Decreases the reference count of node n. If n dies,
  recursively decreases the reference counts of its children.  It is
  used to dispose of a BDD that is no longer needed. It is more
  efficient than Cudd_RecursiveDeref, but it cannot be used on
  ADDs. The greater efficiency comes from being able to assume that no
  constant node will ever die as a result of a call to this
  procedure.]

  SideEffects [None]

  SeeAlso     [Cudd_RecursiveDeref Cudd_DelayedDerefBdd]

******************************************************************************/
void
Cudd_IterDerefBdd(
  DdManager * table,
  DdNode * n)
{
    DdNode *N;
    int ord;
    DdNodePtr *stack = table->stack;
    int SP = 1;

    unsigned int live = table->keys - table->dead;
    if (live > table->peakLiveNodes) {
        table->peakLiveNodes = live;
    }

    N = Cudd_Regular(n);

    do {
#ifdef DD_DEBUG
        assert(N->ref != 0);
#endif

        if (N->ref == 1) {
            N->ref = 0;
            table->dead++;
#ifdef DD_STATS
            table->nodesDropped++;
#endif
            ord = table->perm[N->index];
            stack[SP++] = Cudd_Regular(cuddE(N));
            table->subtables[ord].dead++;
            N = cuddT(N);
        } else {
            cuddSatDec(N->ref);
            N = stack[--SP];
        }
    } while (SP != 0);

} /* end of Cudd_IterDerefBdd */


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

  Synopsis    [Decreases the reference count of BDD node n.]

  Description [Enqueues node n for later dereferencing. If the queue
  is full decreases the reference count of the oldest node N to make
  room for n. If N dies, recursively decreases the reference counts of
  its children.  It is used to dispose of a BDD that is currently not
  needed, but may be useful again in the near future. The dereferencing
  proper is done as in Cudd_IterDerefBdd.]

  SideEffects [None]

  SeeAlso     [Cudd_RecursiveDeref Cudd_IterDerefBdd]

******************************************************************************/
void
Cudd_DelayedDerefBdd(
  DdManager * table,
  DdNode * n)
{
    DdNode *N;
    int ord;
    DdNodePtr *stack;
    int SP;

    unsigned int live = table->keys - table->dead;
    if (live > table->peakLiveNodes) {
        table->peakLiveNodes = live;
    }

    n = Cudd_Regular(n);
#ifdef DD_DEBUG
    assert(n->ref != 0);
#endif

#ifdef DD_NO_DEATH_ROW
    N = n;
#else
    if (cuddIsConstant(n) || n->ref > 1) {
#ifdef DD_DEBUG
        assert(n->ref != 1 && (!cuddIsConstant(n) || n == DD_ONE(table)));
#endif
        cuddSatDec(n->ref);
        return;
    }

    N = table->deathRow[table->nextDead];

    if (N != NULL) {
#endif
#ifdef DD_DEBUG
        assert(!Cudd_IsComplement(N));
#endif
        stack = table->stack;
        SP = 1;
        do {
#ifdef DD_DEBUG
            assert(N->ref != 0);
#endif
            if (N->ref == 1) {
                N->ref = 0;
                table->dead++;
#ifdef DD_STATS
                table->nodesDropped++;
#endif
                ord = table->perm[N->index];
                stack[SP++] = Cudd_Regular(cuddE(N));
                table->subtables[ord].dead++;
                N = cuddT(N);
            } else {
                cuddSatDec(N->ref);
                N = stack[--SP];
            }
        } while (SP != 0);
#ifndef DD_NO_DEATH_ROW
    }
    table->deathRow[table->nextDead] = n;

    /* Udate insertion point. */
    table->nextDead++;
    table->nextDead &= table->deadMask;
#if 0
    if (table->nextDead == table->deathRowDepth) {
        if (table->deathRowDepth < table->looseUpTo / 2) {
            extern void (*MMoutOfMemory)(long);
            void (*saveHandler)(long) = MMoutOfMemory;
            DdNodePtr *newRow;
            MMoutOfMemory = Cudd_OutOfMem;
            newRow = ABC_REALLOC(DdNodePtr,table->deathRow,2*table->deathRowDepth);
            MMoutOfMemory = saveHandler;
            if (newRow == NULL) {
                table->nextDead = 0;
            } else {
                int i;
                table->memused += table->deathRowDepth;
                i = table->deathRowDepth;
                table->deathRowDepth <<= 1;
                for (; i < table->deathRowDepth; i++) {
                    newRow[i] = NULL;
                }
                table->deadMask = table->deathRowDepth - 1;
                table->deathRow = newRow;
            }
        } else {
            table->nextDead = 0;
        }
    }
#endif
#endif

} /* end of Cudd_DelayedDerefBdd */


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

  Synopsis    [Decreases the reference count of ZDD node n.]

  Description [Decreases the reference count of ZDD node n. If n dies,
  recursively decreases the reference counts of its children.  It is
  used to dispose of a ZDD that is no longer needed.]

  SideEffects [None]

  SeeAlso     [Cudd_Deref Cudd_Ref Cudd_RecursiveDeref]

******************************************************************************/
void
Cudd_RecursiveDerefZdd(
  DdManager * table,
  DdNode * n)
{
    DdNode *N;
    int ord;
    DdNodePtr *stack = table->stack;
    int SP = 1;

    N = n;

    do {
#ifdef DD_DEBUG
        assert(N->ref != 0);
#endif

        cuddSatDec(N->ref);
    
        if (N->ref == 0) {
            table->deadZ++;
#ifdef DD_STATS
            table->nodesDropped++;
#endif
#ifdef DD_DEBUG
            assert(!cuddIsConstant(N));
#endif
            ord = table->permZ[N->index];
            stack[SP++] = cuddE(N);
            table->subtableZ[ord].dead++;
            N = cuddT(N);
        } else {
            N = stack[--SP];
        }
    } while (SP != 0);

} /* end of Cudd_RecursiveDerefZdd */


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

  Synopsis    [Decreases the reference count of node.]

  Description [Decreases the reference count of node. It is primarily
  used in recursive procedures to decrease the ref count of a result
  node before returning it. This accomplishes the goal of removing the
  protection applied by a previous Cudd_Ref.]

  SideEffects [None]

  SeeAlso     [Cudd_RecursiveDeref Cudd_RecursiveDerefZdd Cudd_Ref]

******************************************************************************/
void
Cudd_Deref(
  DdNode * node)
{
    node = Cudd_Regular(node);
    cuddSatDec(node->ref);

} /* end of Cudd_Deref */


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

  Synopsis [Checks the unique table for nodes with non-zero reference
  counts.]

  Description [Checks the unique table for nodes with non-zero
  reference counts. It is normally called before Cudd_Quit to make sure
  that there are no memory leaks due to missing Cudd_RecursiveDeref's.
  Takes into account that reference counts may saturate and that the
  basic constants and the projection functions are referenced by the
  manager.  Returns the number of nodes with non-zero reference count.
  (Except for the cases mentioned above.)]

  SideEffects [None]

  SeeAlso     []

******************************************************************************/
int
Cudd_CheckZeroRef(
  DdManager * manager)
{
    int size;
    int i, j;
    int remain; /* the expected number of remaining references to one */
    DdNodePtr *nodelist;
    DdNode *node;
    DdNode *sentinel = &(manager->sentinel);
    DdSubtable *subtable;
    int count = 0;
    int index;

#ifndef DD_NO_DEATH_ROW
    cuddClearDeathRow(manager);
#endif

    /* First look at the BDD/ADD subtables. */
    remain = 1; /* reference from the manager */
    size = manager->size;
    remain += 2 * size; /* reference from the BDD projection functions */

    for (i = 0; i < size; i++) {
        subtable = &(manager->subtables[i]);
        nodelist = subtable->nodelist;
        for (j = 0; (unsigned) j < subtable->slots; j++) {
            node = nodelist[j];
            while (node != sentinel) {
                if (node->ref != 0 && node->ref != DD_MAXREF) {
                    index = (int) node->index;
                    if (node != manager->vars[index]) {
                        count++;
                    } else {
                        if (node->ref != 1) {
                            count++;
                        }
                    }
                }
                node = node->next;
            }
        }
    }

    /* Then look at the ZDD subtables. */
    size = manager->sizeZ;
    if (size) /* references from ZDD universe */
        remain += 2;

    for (i = 0; i < size; i++) {
        subtable = &(manager->subtableZ[i]);
        nodelist = subtable->nodelist;
        for (j = 0; (unsigned) j < subtable->slots; j++) {
            node = nodelist[j];
            while (node != NULL) {
                if (node->ref != 0 && node->ref != DD_MAXREF) {
                    index = (int) node->index;
                    if (node == manager->univ[manager->permZ[index]]) {
                        if (node->ref > 2) {
                            count++;
                        }
                    } else {
                        count++;
                    }
                }
                node = node->next;
            }
        }
    }

    /* Now examine the constant table. Plusinfinity, minusinfinity, and
    ** zero are referenced by the manager. One is referenced by the
    ** manager, by the ZDD universe, and by all projection functions.
    ** All other nodes should have no references.
    */
    nodelist = manager->constants.nodelist;
    for (j = 0; (unsigned) j < manager->constants.slots; j++) {
        node = nodelist[j];
        while (node != NULL) {
            if (node->ref != 0 && node->ref != DD_MAXREF) {
                if (node == manager->one) {
                    if ((int) node->ref != remain) {
                        count++;
                    }
                } else if (node == manager->zero ||
                node == manager->plusinfinity ||
                node == manager->minusinfinity) {
                    if (node->ref != 1) {
                        count++;
                    }
                } else {
                    count++;
                }
            }
            node = node->next;
        }
    }
    return(count);

} /* end of Cudd_CheckZeroRef */


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/* Definition of internal functions                                          */
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/**Function********************************************************************

  Synopsis    [Brings children of a dead node back.]

  Description []

  SideEffects [None]

  SeeAlso     [cuddReclaimZdd]

******************************************************************************/
void
cuddReclaim(
  DdManager * table,
  DdNode * n)
{
    DdNode *N;
    int ord;
    DdNodePtr *stack = table->stack;
    int SP = 1;
    double initialDead = table->dead;

    N = Cudd_Regular(n);

#ifdef DD_DEBUG
    assert(N->ref == 0);
#endif

    do {
        if (N->ref == 0) {
            N->ref = 1;
            table->dead--;
            if (cuddIsConstant(N)) {
                table->constants.dead--;
                N = stack[--SP];
            } else {
                ord = table->perm[N->index];
                stack[SP++] = Cudd_Regular(cuddE(N));
                table->subtables[ord].dead--;
                N = cuddT(N);
            }
        } else {
            cuddSatInc(N->ref);
            N = stack[--SP];
        }
    } while (SP != 0);

    N = Cudd_Regular(n);
    cuddSatDec(N->ref);
    table->reclaimed += initialDead - table->dead;

} /* end of cuddReclaim */


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

  Synopsis    [Brings children of a dead ZDD node back.]

  Description []

  SideEffects [None]

  SeeAlso     [cuddReclaim]

******************************************************************************/
void
cuddReclaimZdd(
  DdManager * table,
  DdNode * n)
{
    DdNode *N;
    int ord;
    DdNodePtr *stack = table->stack;
    int SP = 1;

    N = n;

#ifdef DD_DEBUG
    assert(N->ref == 0);
#endif

    do {
        cuddSatInc(N->ref);

        if (N->ref == 1) {
            table->deadZ--;
            table->reclaimed++;
#ifdef DD_DEBUG
            assert(!cuddIsConstant(N));
#endif
            ord = table->permZ[N->index];
            stack[SP++] = cuddE(N);
            table->subtableZ[ord].dead--;
            N = cuddT(N);
        } else {
            N = stack[--SP];
        }
    } while (SP != 0);

    cuddSatDec(n->ref);

} /* end of cuddReclaimZdd */


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

  Synopsis    [Shrinks the death row.]

  Description [Shrinks the death row by a factor of four.]

  SideEffects [None]

  SeeAlso     [cuddClearDeathRow]

******************************************************************************/
void
cuddShrinkDeathRow(
  DdManager *table)
{
#ifndef DD_NO_DEATH_ROW
    int i;

    if (table->deathRowDepth > 3) {
        for (i = table->deathRowDepth/4; i < table->deathRowDepth; i++) {
            if (table->deathRow[i] == NULL) break;
            Cudd_IterDerefBdd(table,table->deathRow[i]);
            table->deathRow[i] = NULL;
        }
        table->deathRowDepth /= 4;
        table->deadMask = table->deathRowDepth - 1;
        if ((unsigned) table->nextDead > table->deadMask) {
            table->nextDead = 0;
        }
        table->deathRow = ABC_REALLOC(DdNodePtr, table->deathRow,
                                   table->deathRowDepth);
    }
#endif

} /* end of cuddShrinkDeathRow */


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

  Synopsis    [Clears the death row.]

  Description []

  SideEffects [None]

  SeeAlso     [Cudd_DelayedDerefBdd Cudd_IterDerefBdd Cudd_CheckZeroRef
  cuddGarbageCollect]

******************************************************************************/
void
cuddClearDeathRow(
  DdManager *table)
{
#ifndef DD_NO_DEATH_ROW
    int i;

    for (i = 0; i < table->deathRowDepth; i++) {
        if (table->deathRow[i] == NULL) break;
        Cudd_IterDerefBdd(table,table->deathRow[i]);
        table->deathRow[i] = NULL;
    }
#ifdef DD_DEBUG
    for (; i < table->deathRowDepth; i++) {
        assert(table->deathRow[i] == NULL);
    }
#endif
    table->nextDead = 0;
#endif

} /* end of cuddClearDeathRow */


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

  Synopsis    [Checks whether a node is in the death row.]

  Description [Checks whether a node is in the death row. Returns the
  position of the first occurrence if the node is present; -1
  otherwise.]

  SideEffects [None]

  SeeAlso     [Cudd_DelayedDerefBdd cuddClearDeathRow]

******************************************************************************/
int
cuddIsInDeathRow(
  DdManager *dd,
  DdNode *f)
{
#ifndef DD_NO_DEATH_ROW
    int i;

    for (i = 0; i < dd->deathRowDepth; i++) {
        if (f == dd->deathRow[i]) {
            return(i);
        }
    }
#endif

    return(-1);

} /* end of cuddIsInDeathRow */


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

  Synopsis    [Counts how many times a node is in the death row.]

  Description []

  SideEffects [None]

  SeeAlso     [Cudd_DelayedDerefBdd cuddClearDeathRow cuddIsInDeathRow]

******************************************************************************/
int
cuddTimesInDeathRow(
  DdManager *dd,
  DdNode *f)
{
    int count = 0;
#ifndef DD_NO_DEATH_ROW
    int i;

    for (i = 0; i < dd->deathRowDepth; i++) {
        count += f == dd->deathRow[i];
    }
#endif

    return(count);

} /* end of cuddTimesInDeathRow */

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/* Definition of static functions                                            */
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ABC_NAMESPACE_IMPL_END