heapsort.c revision 264042
1/*- 2 * Copyright (c) 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (c) 2014 David T. Chisnall 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 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. 21 * 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 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35#if defined(LIBC_SCCS) && !defined(lint) 36static 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: head/lib/libc/stdlib/heapsort.c 264042 2014-04-02 16:07:48Z theraven $"); 40 41#include <errno.h> 42#include <stddef.h> 43#include <stdlib.h> 44 45#ifdef I_AM_HEAPSORT_B 46#include "block_abi.h" 47#define COMPAR(x, y) CALL_BLOCK(compar, x, y) 48#else 49#define COMPAR(x, y) compar(x, y) 50#endif 51 52/* 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. 58 */ 59#define SWAP(a, b, count, size, tmp) { \ 60 count = size; \ 61 do { \ 62 tmp = *a; \ 63 *a++ = *b; \ 64 *b++ = tmp; \ 65 } while (--count); \ 66} 67 68/* Copy one block of size size to another. */ 69#define COPY(a, b, count, size, tmp1, tmp2) { \ 70 count = size; \ 71 tmp1 = a; \ 72 tmp2 = b; \ 73 do { \ 74 *tmp1++ = *tmp2++; \ 75 } while (--count); \ 76} 77 78/* 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. 81 * 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. 84 */ 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; \ 87 par_i = child_i) { \ 88 child = base + child_i * size; \ 89 if (child_i < nmemb && COMPAR(child, child + size) < 0) { \ 90 child += size; \ 91 ++child_i; \ 92 } \ 93 par = base + par_i * size; \ 94 if (COMPAR(child, par) <= 0) \ 95 break; \ 96 SWAP(par, child, count, size, tmp); \ 97 } \ 98} 99 100/* 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. 107 * 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. 111 * 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. 114 * 115 * XXX Don't break the #define SELECT line, below. Reiser cpp gets upset. 116 */ 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) { \ 121 child += size; \ 122 ++child_i; \ 123 } \ 124 par = base + par_i * size; \ 125 COPY(par, child, count, size, tmp1, tmp2); \ 126 } \ 127 for (;;) { \ 128 child_i = par_i; \ 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); \ 134 break; \ 135 } \ 136 COPY(child, par, count, size, tmp1, tmp2); \ 137 } \ 138} 139 140/* 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. 146 */ 147#ifdef I_AM_HEAPSORT_B 148int 149heapsort_b(vbase, nmemb, size, compar) 150 void *vbase; 151 size_t nmemb, size; 152 DECLARE_BLOCK(int, compar, const void *, const void *); 153#else 154int 155heapsort(vbase, nmemb, size, compar) 156 void *vbase; 157 size_t nmemb, size; 158 int (*compar)(const void *, const void *); 159#endif 160{ 161 size_t cnt, i, j, l; 162 char tmp, *tmp1, *tmp2; 163 char *base, *k, *p, *t; 164 165 if (nmemb <= 1) 166 return (0); 167 168 if (!size) { 169 errno = EINVAL; 170 return (-1); 171 } 172 173 if ((k = malloc(size)) == NULL) 174 return (-1); 175 176 /* 177 * Items are numbered from 1 to nmemb, so offset from size bytes 178 * below the starting address. 179 */ 180 base = (char *)vbase - size; 181 182 for (l = nmemb / 2 + 1; --l;) 183 CREATE(l, nmemb, i, j, t, p, size, cnt, tmp); 184 185 /* 186 * For each element of the heap, save the largest element into its 187 * final slot, save the displaced element (k), then recreate the 188 * heap. 189 */ 190 while (nmemb > 1) { 191 COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2); 192 COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2); 193 --nmemb; 194 SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2); 195 } 196 free(k); 197 return (0); 198} 199