qsort.c

主要进行大规模的电路综合

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

  FileName    [qsort.c]

  PackageName [util]

  Synopsis    [Our own qsort routine.]

  Author      []

  Copyright   [Copyright (c) 1994-1996 The Regents of the Univ. of California.
  All rights reserved.

  Permission is hereby granted, without written agreement and without license
  or royalty fees, to use, copy, modify, and distribute this software and its
  documentation for any purpose, provided that the above copyright notice and
  the following two paragraphs appear in all copies of this software.

  IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR
  DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
  OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF
  CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

  THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
  INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
  FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS ON AN
  "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO PROVIDE
  MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.]

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

#include "util.h"

#ifndef lint
static char rcsid[] UNUSED = "$Id: qsort.c,v 1.1.1.1 2003/02/24 22:24:04 wjiang Exp $";
#endif

#define		THRESH		4		/* threshold for insertion */
#define		MTHRESH		6		/* threshold for median */

static  int		(*qcmp)();		/* the comparison routine */
static  int		qsz;			/* size of each record */
static  int		thresh;			/* THRESHold in chars */
static  int		mthresh;		/* MTHRESHold in chars */
static	void		qst ARGS((char *base, char *max));

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

#undef min
#undef max
/**Function********************************************************************

  Synopsis           [Own version of the system qsort routine.]

  Description [The THRESHold below is the insertion sort threshold, and has
  been adjusted for records of size 48 bytes.  The MTHREShold is where we stop
  finding a better median. First, set up some global parameters for qst to
  share.  Then, quicksort with qst(), and then a cleanup insertion sort
  ourselves.  Sound simple?  It's not...]

  SideEffects        []

  SeeAlso            [qst]

******************************************************************************/
void
qsort(vbase, n, size, compar)
     	void   *vbase;
	size_t n;
	size_t size;
	int    (*compar)();
{
	register char c, *i, *j, *lo, *hi;
	char *min, *max, *base;

	if (n <= 1)
		return;
	base = vbase;
	qsz = size;
	qcmp = compar;
	thresh = qsz * THRESH;
	mthresh = qsz * MTHRESH;
	max = base + n * qsz;
	if (n >= THRESH) {
		qst(base, max);
		hi = base + thresh;
	} else {
		hi = max;
	}
	/*
	 * First put smallest element, which must be in the first THRESH, in
	 * the first position as a sentinel.  This is done just by searching
	 * the first THRESH elements (or the first n if n < THRESH), finding
	 * the min, and swapping it into the first position.
	 */
	for (j = lo = base; (lo += qsz) < hi; )
		if ((*qcmp)(j, lo) > 0)
			j = lo;
	if (j != base) {
		/* swap j into place */
		for (i = base, hi = base + qsz; i < hi; ) {
			c = *j;
			*j++ = *i;
			*i++ = c;
		}
	}
	/*
	 * With our sentinel in place, we now run the following hyper-fast
	 * insertion sort. For each remaining element, min, from [1] to [n-1],
	 * set hi to the index of the element AFTER which this one goes.
	 * Then, do the standard insertion sort shift on a character at a time
	 * basis for each element in the frob.
	 */
	for (min = base; (hi = min += qsz) < max; ) {
		while ((*qcmp)(hi -= qsz, min) > 0)
			/* void */;
		if ((hi += qsz) != min) {
			for (lo = min + qsz; --lo >= min; ) {
				c = *lo;
				for (i = j = lo; (j -= qsz) >= hi; i = j)
					*i = *j;
				*i = c;
			}
		}
	}
}

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

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

  Synopsis           [Effectively perform qsort]

  Description [First, find the median element, and put that one in the first
  place as the discriminator.  (This "median" is just the median of the first,
  last and middle elements).  (Using this median instead of the first element
  is a big win).  Then, the usual partitioning/swapping, followed by moving the
  discriminator into the right place.  Then, figure out the sizes of the two
  partions, do the smaller one recursively and the larger one via a repeat of
  this code.  Stopping when there are less than THRESH elements in a partition
  and cleaning up with an insertion sort (in our caller) is a huge win.  All
  data swaps are done in-line, which is space-losing but time-saving.  (And
  there are only three places where this is done).]

  SideEffects        []

  SeeAlso            [qsort]

******************************************************************************/
static void
qst(base, max)
	char *base;
	char *max;
{
	register char c, *i, *j, *jj;
	register int ii;
	char *mid, *tmp;
	int lo, hi;

	/*
	 * At the top here, lo is the number of characters of elements in the
	 * current partition.  (Which should be max - base).
	 * Find the median of the first, last, and middle element and make
	 * that the middle element.  Set j to largest of first and middle.
	 * If max is larger than that guy, then it's that guy, else compare
	 * max with loser of first and take larger.  Things are set up to
	 * prefer the middle, then the first in case of ties.
	 */
	lo = max - base;		/* number of elements as chars */
	do	{
		mid = i = base + qsz * ((lo / qsz) >> 1);
		if (lo >= mthresh) {
			j = ((*qcmp)((jj = base), i) > 0 ? jj : i);
			if ((*qcmp)(j, (tmp = max - qsz)) > 0) {
				/* switch to first loser */
				j = (j == jj ? i : jj);
				if ((*qcmp)(j, tmp) < 0)
					j = tmp;
			}
			if (j != i) {
				ii = qsz;
				do	{
					c = *i;
					*i++ = *j;
					*j++ = c;
				} while (--ii);
			}
		}
		/*
		 * Semi-standard quicksort partitioning/swapping
		 */
		for (i = base, j = max - qsz; ; ) {
			while (i < mid && (*qcmp)(i, mid) <= 0)
				i += qsz;
			while (j > mid) {
				if ((*qcmp)(mid, j) <= 0) {
					j -= qsz;
					continue;
				}
				tmp = i + qsz;	/* value of i after swap */
				if (i == mid) {
					/* j <-> mid, new mid is j */
					mid = jj = j;
				} else {
					/* i <-> j */
					jj = j;
					j -= qsz;
				}
				goto swap;
			}
			if (i == mid) {
				break;
			} else {
				/* i <-> mid, new mid is i */
				jj = mid;
				tmp = mid = i;	/* value of i after swap */
				j -= qsz;
			}
		swap:
			ii = qsz;
			do	{
				c = *i;
				*i++ = *jj;
				*jj++ = c;
			} while (--ii);
			i = tmp;
		}
		/*
		 * Look at sizes of the two partitions, do the smaller
		 * one first by recursion, then do the larger one by
		 * making sure lo is its size, base and max are update
		 * correctly, and branching back.  But only repeat
		 * (recursively or by branching) if the partition is
		 * of at least size THRESH.
		 */
		i = (j = mid) + qsz;
		if ((lo = j - base) <= (hi = max - i)) {
			if (lo >= thresh)
				qst(base, j);
			base = i;
			lo = hi;
		} else {
			if (hi >= thresh)
				qst(i, max);
			max = j;
		}
	} while (lo >= thresh);
}