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

  FileName    [cuddLevelQ.c]

  PackageName [cudd]

  Synopsis    [Procedure to manage level queues.]

  Description [The functions in this file allow an application to
  easily manipulate a queue where nodes are prioritized by level. The
  emphasis is on efficiency. Therefore, the queue items can have
  variable size.  If the application does not need to attach
  information to the nodes, it can declare the queue items to be of
  type DdQueueItem. Otherwise, it can declare them to be of a
  structure type such that the first three fields are data
  pointers. The third pointer points to the node.  The first two
  pointers are used by the level queue functions. The remaining fields
  are initialized to 0 when a new item is created, and are then left
  to the exclusive use of the application. On the DEC Alphas the three
  pointers must be 32-bit pointers when CUDD is compiled with 32-bit
  pointers.  The level queue functions make sure that each node
  appears at most once in the queue. They do so by keeping a hash
  table where the node is used as key.  Queue items are recycled via a
  free list for efficiency.
  
  Internal procedures provided by this module:
                <ul>
		<li> cuddLevelQueueInit()
		<li> cuddLevelQueueQuit()
		<li> cuddLevelQueueEnqueue()
		<li> cuddLevelQueueDequeue()
		</ul>
  Static procedures included in this module:
		<ul>
		<li> hashLookup()
		<li> hashInsert()
		<li> hashDelete()
		<li> hashResize()
		</ul>
		]

  SeeAlso     []

  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"

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


/*---------------------------------------------------------------------------*/
/* Stucture declarations                                                     */
/*---------------------------------------------------------------------------*/

/*---------------------------------------------------------------------------*/
/* Type declarations                                                         */
/*---------------------------------------------------------------------------*/

/*---------------------------------------------------------------------------*/
/* Variable declarations                                                     */
/*---------------------------------------------------------------------------*/

#ifndef lint
static char rcsid[] DD_UNUSED = "$Id: cuddLevelQ.c,v 1.1 2002/09/17 21:58:48 dlm Exp $";
#endif

/*---------------------------------------------------------------------------*/
/* Macro declarations                                                        */
/*---------------------------------------------------------------------------*/


/**Macro***********************************************************************

  Synopsis    [Hash function for the table of a level queue.]

  Description [Hash function for the table of a level queue.]

  SideEffects [None]

  SeeAlso     [hashInsert hashLookup hashDelete]

******************************************************************************/
#if SIZEOF_VOID_P == 8 && SIZEOF_INT == 4
#define lqHash(key,shift) \
(((unsigned)(unsigned long)(key) * DD_P1) >> (shift))
#else
#define lqHash(key,shift) \
(((unsigned)(key) * DD_P1) >> (shift))
#endif


/**AutomaticStart*************************************************************/

/*---------------------------------------------------------------------------*/
/* Static function prototypes                                                */
/*---------------------------------------------------------------------------*/

static DdQueueItem * hashLookup ARGS((DdLevelQueue *queue, void *key));
static int hashInsert ARGS((DdLevelQueue *queue, DdQueueItem *item));
static void hashDelete ARGS((DdLevelQueue *queue, DdQueueItem *item));
static int hashResize ARGS((DdLevelQueue *queue));

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


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


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

  Synopsis    [Initializes a level queue.]

  Description [Initializes a level queue. A level queue is a queue
  where inserts are based on the levels of the nodes. Within each
  level the policy is FIFO. Level queues are useful in traversing a
  BDD top-down. Queue items are kept in a free list when dequeued for
  efficiency. Returns a pointer to the new queue if successful; NULL
  otherwise.]

  SideEffects [None]

  SeeAlso     [cuddLevelQueueQuit cuddLevelQueueEnqueue cuddLevelQueueDequeue]

******************************************************************************/
DdLevelQueue *
cuddLevelQueueInit(
  int  levels /* number of levels */,
  int  itemSize /* size of the item */,
  int  numBuckets /* initial number of hash buckets */)
{
    DdLevelQueue *queue;
    int logSize;

    queue = ALLOC(DdLevelQueue,1);
    if (queue == NULL)
	return(NULL);
#ifdef __osf__
#pragma pointer_size save
#pragma pointer_size short
#endif
    /* Keep pointers to the insertion points for all levels. */
    queue->last = ALLOC(DdQueueItem *, levels);
#ifdef __osf__
#pragma pointer_size restore
#endif
    if (queue->last == NULL) {
	FREE(queue);
	return(NULL);
    }
    /* Use a hash table to test for uniqueness. */
    if (numBuckets < 2) numBuckets = 2;
    logSize = cuddComputeFloorLog2(numBuckets);
    queue->numBuckets = 1 << logSize;
    queue->shift = sizeof(int) * 8 - logSize;
#ifdef __osf__
#pragma pointer_size save
#pragma pointer_size short
#endif
    queue->buckets = ALLOC(DdQueueItem *, queue->numBuckets);
#ifdef __osf__
#pragma pointer_size restore
#endif
    if (queue->buckets == NULL) {
	FREE(queue->last);
	FREE(queue);
	return(NULL);
    }
#ifdef __osf__
#pragma pointer_size save
#pragma pointer_size short
#endif
    memset(queue->last, 0, levels * sizeof(DdQueueItem *));
    memset(queue->buckets, 0, queue->numBuckets * sizeof(DdQueueItem *));
#ifdef __osf__
#pragma pointer_size restore
#endif
    queue->first = NULL;
    queue->freelist = NULL;
    queue->levels = levels;
    queue->itemsize = itemSize;
    queue->size = 0;
    queue->maxsize = queue->numBuckets * DD_MAX_SUBTABLE_DENSITY;
    return(queue);

} /* end of cuddLevelQueueInit */


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

  Synopsis    [Shuts down a level queue.]

  Description [Shuts down a level queue and releases all the
  associated memory.]

  SideEffects [None]

  SeeAlso     [cuddLevelQueueInit]

******************************************************************************/
void
cuddLevelQueueQuit(
  DdLevelQueue * queue)
{
    DdQueueItem *item;

    while (queue->freelist != NULL) {
	item = queue->freelist;
	queue->freelist = item->next;
	FREE(item);
    }
    while (queue->first != NULL) {
	item = (DdQueueItem *) queue->first;
	queue->first = item->next;
	FREE(item);
    }
    FREE(queue->buckets);
    FREE(queue->last);
    FREE(queue);
    return;

} /* end of cuddLevelQueueQuit */


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

  Synopsis    [Inserts a new key in a level queue.]

  Description [Inserts a new key in a level queue. A new entry is
  created in the queue only if the node is not already
  enqueued. Returns a pointer to the queue item if successful; NULL
  otherwise.]

  SideEffects [None]

  SeeAlso     [cuddLevelQueueInit cuddLevelQueueDequeue]

******************************************************************************/
void *
cuddLevelQueueEnqueue(
  DdLevelQueue * queue /* level queue */,
  void * key /* key to be enqueued */,
  int  level /* level at which to insert */)
{
    int plevel;
    DdQueueItem *item;

#ifdef DD_DEBUG
    assert(level < queue->levels);
#endif
    /* Check whether entry for this node exists. */
    item = hashLookup(queue,key);
    if (item != NULL) return(item);

    /* Get a free item from either the free list or the memory manager. */
    if (queue->freelist == NULL) {
	item = (DdQueueItem *) ALLOC(char, queue->itemsize);
	if (item == NULL)
	    return(NULL);
    } else {
	item = queue->freelist;
	queue->freelist = item->next;
    }
    /* Initialize. */
    memset(item, 0, queue->itemsize);
    item->key = key;
    /* Update stats. */
    queue->size++;

    if (queue->last[level]) {
	/* There are already items for this level in the queue. */
	item->next = queue->last[level]->next;
	queue->last[level]->next = item;
    } else {
	/* There are no items at the current level.  Look for the first
	** non-empty level preceeding this one. */
	plevel = level;
	while (plevel != 0 && queue->last[plevel] == NULL)
	    plevel--;
	if (queue->last[plevel] == NULL) {
	    /* No element precedes this one in the queue. */
	    item->next = (DdQueueItem *) queue->first;
	    queue->first = item;
	} else {
	    item->next = queue->last[plevel]->next;
	    queue->last[plevel]->next = item;
	}
    }
    queue->last[level] = item;

    /* Insert entry for the key in the hash table. */
    if (hashInsert(queue,item) == 0) {
	return(NULL);
    }
    return(item);

} /* end of cuddLevelQueueEnqueue */


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

  Synopsis    [Remove an item from the front of a level queue.]

  Description [Remove an item from the front of a level queue.]

  SideEffects [None]

  SeeAlso     [cuddLevelQueueEnqueue]

******************************************************************************/
void
cuddLevelQueueDequeue(
  DdLevelQueue * queue,
  int  level)
{
    DdQueueItem *item = (DdQueueItem *) queue->first;

    /* Delete from the hash table. */
    hashDelete(queue,item);

    /* Since we delete from the front, if this is the last item for
    ** its level, there are no other items for the same level. */
    if (queue->last[level] == item)
	queue->last[level] = NULL;

    queue->first = item->next;
    /* Put item on the free list. */
    item->next = queue->freelist;
    queue->freelist = item;
    /* Update stats. */
    queue->size--;
    return;

} /* end of cuddLevelQueueDequeue */


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


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

  Synopsis    [Looks up a key in the hash table of a level queue.]

  Description [Looks up a key in the hash table of a level queue. Returns
  a pointer to the item with the given key if the key is found; NULL
  otherwise.]

  SideEffects [None]

  SeeAlso     [cuddLevelQueueEnqueue hashInsert]

******************************************************************************/
static DdQueueItem *
hashLookup(
  DdLevelQueue * queue,
  void * key)
{
    int posn;
    DdQueueItem *item;

    posn = lqHash(key,queue->shift);
    item = queue->buckets[posn];

    while (item != NULL) {
	if (item->key == key) {
	    return(item);
	}
	item = item->cnext;
    }
    return(NULL);

} /* end of hashLookup */


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

  Synopsis    [Inserts an item in the hash table of a level queue.]

  Description [Inserts an item in the hash table of a level queue. Returns
  1 if successful; 0 otherwise. No check is performed to see if an item with
  the same key is already in the hash table.]

  SideEffects [None]

  SeeAlso     [cuddLevelQueueEnqueue]

******************************************************************************/
static int
hashInsert(
  DdLevelQueue * queue,
  DdQueueItem * item)
{
    int result;
    int posn;

    if (queue->size > queue->maxsize) {
	result = hashResize(queue);
	if (result == 0) return(0);
    }

    posn = lqHash(item->key,queue->shift);
    item->cnext = queue->buckets[posn];
    queue->buckets[posn] = item;

    return(1);
    
} /* end of hashInsert */


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

  Synopsis    [Removes an item from the hash table of a level queue.]

  Description [Removes an item from the hash table of a level queue.
  Nothing is done if the item is not in the table.]

  SideEffects [None]

  SeeAlso     [cuddLevelQueueDequeue hashInsert]

******************************************************************************/
static void
hashDelete(
  DdLevelQueue * queue,
  DdQueueItem * item)
{
    int posn;
    DdQueueItem *prevItem;

    posn = lqHash(item->key,queue->shift);
    prevItem = queue->buckets[posn];

    if (prevItem == NULL) return;
    if (prevItem == item) {
	queue->buckets[posn] = prevItem->cnext;
	return;
    }

    while (prevItem->cnext != NULL) {
	if (prevItem->cnext == item) {
	    prevItem->cnext = item->cnext;
	    return;
	}
	prevItem = prevItem->cnext;
    }
    return;

} /* end of hashDelete */


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

  Synopsis    [Resizes the hash table of a level queue.]

  Description [Resizes the hash table of a level queue. Returns 1 if
  successful; 0 otherwise.]

  SideEffects [None]

  SeeAlso     [hashInsert]

******************************************************************************/
static int
hashResize(
  DdLevelQueue * queue)
{
    int j;
    int posn;
    DdQueueItem *item;
    DdQueueItem *next;
    int numBuckets;
#ifdef __osf__
#pragma pointer_size save
#pragma pointer_size short
#endif
    DdQueueItem **buckets;
    DdQueueItem **oldBuckets = queue->buckets;
#ifdef __osf__
#pragma pointer_size restore
#endif
    int shift;
    int oldNumBuckets = queue->numBuckets;
    extern void (*MMoutOfMemory)(long);
    void (*saveHandler)(long);

    /* Compute the new size of the subtable. */
    numBuckets = oldNumBuckets << 1;
    saveHandler = MMoutOfMemory;
    MMoutOfMemory = Cudd_OutOfMem;
#ifdef __osf__
#pragma pointer_size save
#pragma pointer_size short
#endif
    buckets = queue->buckets = ALLOC(DdQueueItem *, numBuckets);
    if (buckets == NULL) {
	queue->maxsize <<= 1;
	return(1);
    }

    queue->numBuckets = numBuckets;
    shift = --(queue->shift);
    queue->maxsize <<= 1;
    memset(buckets, 0, numBuckets * sizeof(DdQueueItem *));
#ifdef __osf__
#pragma pointer_size restore
#endif
    for (j = 0; j < oldNumBuckets; j++) {
	item = oldBuckets[j];
	while (item != NULL) {
	    next = item->cnext;
	    posn = lqHash(item->key, shift);
	    item->cnext = buckets[posn];
	    buckets[posn] = item;
	    item = next;
	}
    }
    FREE(oldBuckets);
    return(1);

} /* end of hashResize */
