2 * Copyright (c) 1991, 1993
3 * The Regents of the University of California. All rights reserved.
4 * Copyright (c) 2014 David T. Chisnall
7 * This code is derived from software contributed to Berkeley by
8 * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias.
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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35 #if defined(LIBC_SCCS) && !defined(lint)
36 static char sccsid[] = "@(#)heapsort.c 8.1 (Berkeley) 6/4/93";
37 #endif /* LIBC_SCCS and not lint */
38 #include <sys/cdefs.h>
39 __FBSDID("$FreeBSD$");
45 #ifdef I_AM_HEAPSORT_B
46 #include "block_abi.h"
47 #define COMPAR(x, y) CALL_BLOCK(compar, x, y)
49 #define COMPAR(x, y) compar(x, y)
53 * Swap two areas of size number of bytes. Although qsort(3) permits random
54 * blocks of memory to be sorted, sorting pointers is almost certainly the
55 * common case (and, were it not, could easily be made so). Regardless, it
56 * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer
57 * arithmetic gets lost in the time required for comparison function calls.
59 #define SWAP(a, b, count, size, tmp) { \
68 /* Copy one block of size size to another. */
69 #define COPY(a, b, count, size, tmp1, tmp2) { \
79 * Build the list into a heap, where a heap is defined such that for
80 * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N.
82 * There two cases. If j == nmemb, select largest of Ki and Kj. If
83 * j < nmemb, select largest of Ki, Kj and Kj+1.
85 #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \
86 for (par_i = initval; (child_i = par_i * 2) <= nmemb; \
88 child = base + child_i * size; \
89 if (child_i < nmemb && COMPAR(child, child + size) < 0) { \
93 par = base + par_i * size; \
94 if (COMPAR(child, par) <= 0) \
96 SWAP(par, child, count, size, tmp); \
101 * Select the top of the heap and 'heapify'. Since by far the most expensive
102 * action is the call to the compar function, a considerable optimization
103 * in the average case can be achieved due to the fact that k, the displaced
104 * elememt, is ususally quite small, so it would be preferable to first
105 * heapify, always maintaining the invariant that the larger child is copied
106 * over its parent's record.
108 * Then, starting from the *bottom* of the heap, finding k's correct place,
109 * again maintianing the invariant. As a result of the invariant no element
110 * is 'lost' when k is assigned its correct place in the heap.
112 * The time savings from this optimization are on the order of 15-20% for the
113 * average case. See Knuth, Vol. 3, page 158, problem 18.
115 * XXX Don't break the #define SELECT line, below. Reiser cpp gets upset.
117 #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \
118 for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \
119 child = base + child_i * size; \
120 if (child_i < nmemb && COMPAR(child, child + size) < 0) { \
124 par = base + par_i * size; \
125 COPY(par, child, count, size, tmp1, tmp2); \
129 par_i = child_i / 2; \
130 child = base + child_i * size; \
131 par = base + par_i * size; \
132 if (child_i == 1 || COMPAR(k, par) < 0) { \
133 COPY(child, k, count, size, tmp1, tmp2); \
136 COPY(child, par, count, size, tmp1, tmp2); \
141 * Heapsort -- Knuth, Vol. 3, page 145. Runs in O (N lg N), both average
142 * and worst. While heapsort is faster than the worst case of quicksort,
143 * the BSD quicksort does median selection so that the chance of finding
144 * a data set that will trigger the worst case is nonexistent. Heapsort's
145 * only advantage over quicksort is that it requires little additional memory.
147 #ifdef I_AM_HEAPSORT_B
149 heapsort_b(vbase, nmemb, size, compar)
152 DECLARE_BLOCK(int, compar, const void *, const void *);
155 heapsort(vbase, nmemb, size, compar)
158 int (*compar)(const void *, const void *);
162 char tmp, *tmp1, *tmp2;
163 char *base, *k, *p, *t;
173 if ((k = malloc(size)) == NULL)
177 * Items are numbered from 1 to nmemb, so offset from size bytes
178 * below the starting address.
180 base = (char *)vbase - size;
182 for (l = nmemb / 2 + 1; --l;)
183 CREATE(l, nmemb, i, j, t, p, size, cnt, tmp);
186 * For each element of the heap, save the largest element into its
187 * final slot, save the displaced element (k), then recreate the
191 COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2);
192 COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2);
194 SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2);