96 lines
2.5 KiB
C
96 lines
2.5 KiB
C
/*
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* This is an optimized version of the following C++ program:
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*
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* http://keithlea.com/javabench/src/cpp/hash.cpp
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*
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* Keith in his benchmark (http://keithlea.com/javabench/data) showed that the
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* Java implementation is twice as fast as the C++ version. In fact, this is
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* only because the C++ implementation is substandard. Most importantly, Keith
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* is using "sprintf()" to convert an integer to a string, which is known to be
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* extremely inefficient.
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*/
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#include <stdio.h>
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#include "khash.h"
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KHASH_MAP_INIT_STR(str, int)
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inline void int2str(int c, int base, char *ret)
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{
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const char *tab = "0123456789abcdef";
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if (c == 0) ret[0] = '0', ret[1] = 0;
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else {
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int l, x, y;
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char buf[16];
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for (l = 0, x = c < 0? -c : c; x > 0; x /= base) buf[l++] = tab[x%base];
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if (c < 0) buf[l++] = '-';
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for (x = l - 1, y = 0; x >= 0; --x) ret[y++] = buf[x];
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ret[y] = 0;
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}
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}
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#ifndef _USE_STRDUP
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#define BLOCK_SIZE 0x100000
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int main(int argc, char *argv[])
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{
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char **mem = 0;
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int i, l, n = 1000000, ret, block_end = 0, curr = 0, c = 0;
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khash_t(str) *h;
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h = kh_init(str);
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if (argc > 1) n = atoi(argv[1]);
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mem = malloc(sizeof(void*));
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mem[0] = malloc(BLOCK_SIZE); // memory buffer to avoid memory fragmentation
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curr = block_end = 0;
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for (i = 1; i <= n; ++i) {
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char buf[16];
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int2str(i, 16, buf);
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khint_t k = kh_put(str, h, buf, &ret);
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l = strlen(buf) + 1;
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if (block_end + l > BLOCK_SIZE) {
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++curr; block_end = 0;
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mem = realloc(mem, (curr + 1) * sizeof(void*));
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mem[curr] = malloc(BLOCK_SIZE);
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}
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memcpy(mem[curr] + block_end, buf, l);
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kh_key(h, k) = mem[curr] + block_end;
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block_end += l;
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kh_val(h, k) = i;
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}
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for (i = 1; i <= n; ++i) {
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char buf[16];
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int2str(i, 10, buf);
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khint_t k = kh_get(str, h, buf);
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if (k != kh_end(h)) ++c;
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}
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printf("%d\n", c);
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for (ret = 0; ret <= curr; ++ret) free(mem[ret]);
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free(mem);
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kh_destroy(str, h);
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return 0;
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}
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#else // _USE_STRDUP
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int main(int argc, char *argv[])
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{
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int i, l, n = 1000000, ret, c = 0;
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khash_t(str) *h;
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khint_t k;
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h = kh_init(str);
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if (argc > 1) n = atoi(argv[1]);
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for (i = 1; i <= n; ++i) {
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char buf[16];
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int2str(i, 16, buf);
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k = kh_put(str, h, strdup(buf), &ret);
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kh_val(h, k) = i;
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}
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for (i = 1; i <= n; ++i) {
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char buf[16];
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int2str(i, 10, buf);
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k = kh_get(str, h, buf);
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if (k != kh_end(h)) ++c;
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}
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for (k = kh_begin(h); k != kh_end(h); ++k) // explicitly freeing memory takes 10-20% CPU time.
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if (kh_exist(h, k)) free((char*)kh_key(h, k));
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printf("%d\n", c);
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kh_destroy(str, h);
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return 0;
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}
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#endif
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