1 /*- 2 * Copyright (c) 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * @(#)heapsort.c 8.1 (Berkeley) 6/4/93 37 */ 38 39 #include <errno.h> 40 #include <stddef.h> 41 #include <stdlib.h> 42 43 /* 44 * Swap two areas of size number of bytes. Although qsort(3) permits random 45 * blocks of memory to be sorted, sorting pointers is almost certainly the 46 * common case (and, were it not, could easily be made so). Regardless, it 47 * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer 48 * arithmetic gets lost in the time required for comparison function calls. 49 */ 50 #define SWAP(a, b, count, size, tmp) { \ 51 count = size; \ 52 do { \ 53 tmp = *a; \ 54 *a++ = *b; \ 55 *b++ = tmp; \ 56 } while (--count); \ 57 } 58 59 /* Copy one block of size size to another. */ 60 #define COPY(a, b, count, size, tmp1, tmp2) { \ 61 count = size; \ 62 tmp1 = a; \ 63 tmp2 = b; \ 64 do { \ 65 *tmp1++ = *tmp2++; \ 66 } while (--count); \ 67 } 68 69 /* 70 * Build the list into a heap, where a heap is defined such that for 71 * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N. 72 * 73 * There two cases. If j == nmemb, select largest of Ki and Kj. If 74 * j < nmemb, select largest of Ki, Kj and Kj+1. 75 */ 76 #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \ 77 for (par_i = initval; (child_i = par_i * 2) <= nmemb; \ 78 par_i = child_i) { \ 79 child = base + child_i * size; \ 80 if (child_i < nmemb && compar(child, child + size) < 0) { \ 81 child += size; \ 82 ++child_i; \ 83 } \ 84 par = base + par_i * size; \ 85 if (compar(child, par) <= 0) \ 86 break; \ 87 SWAP(par, child, count, size, tmp); \ 88 } \ 89 } 90 91 /* 92 * Select the top of the heap and 'heapify'. Since by far the most expensive 93 * action is the call to the compar function, a considerable optimization 94 * in the average case can be achieved due to the fact that k, the displaced 95 * elememt, is ususally quite small, so it would be preferable to first 96 * heapify, always maintaining the invariant that the larger child is copied 97 * over its parent's record. 98 * 99 * Then, starting from the *bottom* of the heap, finding k's correct place, 100 * again maintianing the invariant. As a result of the invariant no element 101 * is 'lost' when k is assigned its correct place in the heap. 102 * 103 * The time savings from this optimization are on the order of 15-20% for the 104 * average case. See Knuth, Vol. 3, page 158, problem 18. 105 * 106 * XXX Don't break the #define SELECT line, below. Reiser cpp gets upset. 107 */ 108 #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \ 109 for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \ 110 child = base + child_i * size; \ 111 if (child_i < nmemb && compar(child, child + size) < 0) { \ 112 child += size; \ 113 ++child_i; \ 114 } \ 115 par = base + par_i * size; \ 116 COPY(par, child, count, size, tmp1, tmp2); \ 117 } \ 118 for (;;) { \ 119 child_i = par_i; \ 120 par_i = child_i / 2; \ 121 child = base + child_i * size; \ 122 par = base + par_i * size; \ 123 if (child_i == 1 || compar(k, par) < 0) { \ 124 COPY(child, k, count, size, tmp1, tmp2); \ 125 break; \ 126 } \ 127 COPY(child, par, count, size, tmp1, tmp2); \ 128 } \ 129 } 130 131 /* 132 * Heapsort -- Knuth, Vol. 3, page 145. Runs in O (N lg N), both average 133 * and worst. While heapsort is faster than the worst case of quicksort, 134 * the BSD quicksort does median selection so that the chance of finding 135 * a data set that will trigger the worst case is nonexistent. Heapsort's 136 * only advantage over quicksort is that it requires little additional memory. 137 */ 138 int 139 heapsort(vbase, nmemb, size, compar) 140 void *vbase; 141 size_t nmemb, size; 142 int (*compar) __P((const void *, const void *)); 143 { 144 register int cnt, i, j, l; 145 register char tmp, *tmp1, *tmp2; 146 char *base, *k, *p, *t; 147 148 if (nmemb <= 1) 149 return (0); 150 151 if (!size) { 152 errno = EINVAL; 153 return (-1); 154 } 155 156 if ((k = malloc(size)) == NULL) 157 return (-1); 158 159 /* 160 * Items are numbered from 1 to nmemb, so offset from size bytes 161 * below the starting address. 162 */ 163 base = (char *)vbase - size; 164 165 for (l = nmemb / 2 + 1; --l;) 166 CREATE(l, nmemb, i, j, t, p, size, cnt, tmp); 167 168 /* 169 * For each element of the heap, save the largest element into its 170 * final slot, save the displaced element (k), then recreate the 171 * heap. 172 */ 173 while (nmemb > 1) { 174 COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2); 175 COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2); 176 --nmemb; 177 SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2); 178 } 179 free(k); 180 return (0); 181 } 182