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32 * @(#)merge.c 8.2 (Berkeley) 2/14/94
33 * $FreeBSD: src/lib/libc/stdlib/merge.c,v 1.8 2007/01/09 00:28:10 imp Exp $
34 * $DragonFly: src/lib/libc/stdlib/merge.c,v 1.6 2005/11/20 12:37:48 swildner Exp $
38 * Hybrid exponential search/linear search merge sort with hybrid
39 * natural/pairwise first pass. Requires about .3% more comparisons
40 * for random data than LSMS with pairwise first pass alone.
41 * It works for objects as small as two bytes.
45 #define THRESHOLD 16 /* Best choice for natural merge cut-off. */
47 /* #define NATURAL to get hybrid natural merge.
48 * (The default is pairwise merging.)
51 #include <sys/types.h>
57 static void setup(u_char *, u_char *, size_t, size_t,
58 int (*)(const void *, const void *));
59 static void insertionsort(u_char *, size_t, size_t,
60 int (*)(const void *, const void *));
62 #define ISIZE sizeof(int)
63 #define PSIZE sizeof(u_char *)
64 #define ICOPY_LIST(src, dst, last) \
66 *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE; \
68 #define ICOPY_ELT(src, dst, i) \
70 *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE; \
73 #define CCOPY_LIST(src, dst, last) \
77 #define CCOPY_ELT(src, dst, i) \
83 * Find the next possible pointer head. (Trickery for forcing an array
84 * to do double duty as a linked list when objects do not align with word
87 /* Assumption: PSIZE is a power of 2. */
88 #define EVAL(p) (u_char **) \
90 (((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))
93 * Arguments are as for qsort.
96 mergesort(void *base, size_t nmemb, size_t size,
97 int (*cmp)(const void *, const void *))
102 u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
103 u_char *list2, *list1, *p2, *p, *last, **p1;
105 if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */
115 * Stupid subtraction for the Cray.
118 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
121 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
125 setup(list1, list2, nmemb, size, cmp);
126 last = list2 + nmemb * size;
128 while (*EVAL(list2) != last) {
131 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
134 f2 = l1 = list1 + (p2 - list2);
137 l2 = list1 + (p2 - list2);
138 while (f1 < l1 && f2 < l2) {
139 if ((*cmp)(f1, f2) <= 0) {
148 if (!big) { /* here i = 0 */
149 while ((b += size) < t && cmp(q, b) >sense)
155 EXPONENTIAL: for (i = size; ; i <<= 1)
156 if ((p = (b + i)) >= t) {
157 if ((p = t - size) > b &&
158 (*cmp)(q, p) <= sense)
163 } else if ((*cmp)(q, p) <= sense) {
171 i = (((t - b) / size) >> 1) * size;
172 if ((*cmp)(q, p = b + i) <= sense)
178 FASTCASE: while (i > size)
180 p = b + (i >>= 1)) <= sense)
189 ICOPY_LIST(f2, tp2, b);
190 ICOPY_ELT(f1, tp2, i);
192 CCOPY_LIST(f2, tp2, b);
193 CCOPY_ELT(f1, tp2, i);
197 ICOPY_LIST(f1, tp2, b);
198 ICOPY_ELT(f2, tp2, i);
200 CCOPY_LIST(f1, tp2, b);
201 CCOPY_ELT(f2, tp2, i);
207 ICOPY_LIST(f2, tp2, l2);
209 CCOPY_LIST(f2, tp2, l2);
210 } else if (f1 < l1) {
212 ICOPY_LIST(f1, tp2, l1);
214 CCOPY_LIST(f1, tp2, l1);
218 tp2 = list1; /* swap list1, list2 */
221 last = list2 + nmemb*size;
224 memmove(list2, list1, nmemb*size);
231 #define swap(a, b) { \
235 tmp = *a; *a++ = *s; *s++ = tmp; \
239 #define reverse(bot, top) { \
244 tmp = *bot; *bot++ = *s; *s++ = tmp; \
251 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of
252 * increasing order, list2 in a corresponding linked list. Checks for runs
253 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL
254 * is defined. Otherwise simple pairwise merging is used.)
257 setup(u_char *list1, u_char *list2, size_t n, size_t size,
258 int (*cmp)(const void *, const void *))
260 int i, length, size2, tmp, sense;
261 u_char *f1, *f2, *s, *l2, *last, *p2;
265 insertionsort(list1, n, size, cmp);
266 *EVAL(list2) = (u_char*) list2 + n*size;
270 * Avoid running pointers out of bounds; limit n to evens
274 insertionsort(list1 + (n - i) * size, i, size, cmp);
275 last = list1 + size * (n - i);
276 *EVAL(list2 + (last - list1)) = list2 + n * size;
281 sense = (cmp(f1, f1 + size) > 0);
282 for (; f1 < last; sense = !sense) {
284 /* Find pairs with same sense. */
285 for (f2 = f1 + size2; f2 < last; f2 += size2) {
286 if ((cmp(f2, f2+ size) > 0) != sense)
290 if (length < THRESHOLD) { /* Pairwise merge */
292 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
294 swap (f1, f1 + size);
295 } while ((f1 += size2) < f2);
296 } else { /* Natural merge */
298 for (f2 = f1 + size2; f2 < l2; f2 += size2) {
299 if ((cmp(f2-size, f2) > 0) != sense) {
300 p2 = *EVAL(p2) = f2 - list1 + list2;
302 reverse(f1, f2-size);
307 reverse (f1, f2-size);
309 if (f2 < last || cmp(f2 - size, f2) > 0)
310 p2 = *EVAL(p2) = f2 - list1 + list2;
312 p2 = *EVAL(p2) = list2 + n*size;
315 #else /* pairwise merge only. */
316 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
317 p2 = *EVAL(p2) = p2 + size2;
318 if (cmp (f1, f1 + size) > 0)
325 * This is to avoid out-of-bounds addresses in sorting the
329 insertionsort(u_char *a, size_t n, size_t size,
330 int (*cmp)(const void *, const void *))
332 u_char *ai, *s, *t, *u, tmp;
335 for (ai = a+size; --n >= 1; ai += size)
336 for (t = ai; t > a; t -= size) {