C verions of Keith's C++ progs; see inner comments

khash_keith.c

@@ -0,0 +1,95 @@
+/*
+ * This is an optimized version of the following C++ program:
+ *
+ *   http://keithlea.com/javabench/src/cpp/hash.cpp
+ *
+ * Keith in his benchmark (http://keithlea.com/javabench/data) showed that the
+ * Java implementation is twice as fast as the C++ version. In fact, this is
+ * only because the C++ implementation is substandard. Most importantly, Keith
+ * is using "sprintf()" to convert an integer to a string, which is known to be
+ * extremely inefficient.
+ */
+#include <stdio.h>
+#include "khash.h"
+KHASH_MAP_INIT_STR(str, int)
+
+inline void int2str(int c, int base, char *ret)
+{
+	const char *tab = "0123456789abcdef";
+	if (c == 0) ret[0] = '0', ret[1] = 0;
+	else {
+		int l, x, y;
+		char buf[16];
+		for (l = 0, x = c < 0? -c : c; x > 0; x /= base) buf[l++] = tab[x%base];
+		if (c < 0) buf[l++] = '-';
+		for (x = l - 1, y = 0; x >= 0; --x) ret[y++] = buf[x];
+		ret[y] = 0;
+	}
+}
+
+#ifndef _USE_STRDUP
+#define BLOCK_SIZE 0x100000
+int main(int argc, char *argv[])
+{
+	char **mem = 0;
+	int i, l, n = 1000000, ret, block_end = 0, curr = 0, c = 0;
+	khash_t(str) *h;
+	h = kh_init(str);
+	if (argc > 1) n = atoi(argv[1]);
+	mem = malloc(sizeof(void*));
+	mem[0] = malloc(BLOCK_SIZE); // memory buffer to avoid memory fragmentation
+	curr = block_end = 0;
+	for (i = 1; i <= n; ++i) {
+		char buf[16];
+		int2str(i, 16, buf);
+		khint_t k = kh_put(str, h, buf, &ret);
+		l = strlen(buf) + 1;
+		if (block_end + l > BLOCK_SIZE) {
+			++curr; block_end = 0;
+			mem = realloc(mem, (curr + 1) * sizeof(void*));
+			mem[curr] = malloc(BLOCK_SIZE);
+		}
+		memcpy(mem[curr] + block_end, buf, l);
+		kh_key(h, k) = mem[curr] + block_end;
+		block_end += l;
+		kh_val(h, k) = i;
+	}
+	for (i = 1; i <= n; ++i) {
+		char buf[16];
+		int2str(i, 10, buf);
+		khint_t k = kh_get(str, h, buf);
+		if (k != kh_end(h)) ++c;
+	}
+	printf("%d\n", c);
+	for (ret = 0; ret <= curr; ++ret) free(mem[ret]);
+	free(mem);
+	kh_destroy(str, h);
+	return 0;
+}
+#else // _USE_STRDUP
+int main(int argc, char *argv[])
+{
+	int i, l, n = 1000000, ret, c = 0;
+	khash_t(str) *h;
+	khint_t k;
+	h = kh_init(str);
+	if (argc > 1) n = atoi(argv[1]);
+	for (i = 1; i <= n; ++i) {
+		char buf[16];
+		int2str(i, 16, buf);
+		k = kh_put(str, h, strdup(buf), &ret);
+		kh_val(h, k) = i;
+	}
+	for (i = 1; i <= n; ++i) {
+		char buf[16];
+		int2str(i, 10, buf);
+		k = kh_get(str, h, buf);
+		if (k != kh_end(h)) ++c;
+	}
+	for (k = kh_begin(h); k != kh_end(h); ++k) // explicitly freeing memory takes 10-20% CPU time.
+		if (kh_exist(h, k)) free((char*)kh_key(h, k));
+	printf("%d\n", c);
+	kh_destroy(str, h);
+	return 0;
+}
+#endif

khash_keith2.c

@@ -0,0 +1,67 @@
+/*
+ * This is an optimized version of the following C++ program:
+ *
+ *   http://keithlea.com/javabench/src/cpp/hash.cpp
+ *
+ * Keith in his benchmark (http://keithlea.com/javabench/data) showed that the
+ * Java implementation is twice as fast as the C++ version. In fact, this is
+ * only because the C++ implementation is substandard. Most importantly, Keith
+ * is using "sprintf()" to convert an integer to a string, which is known to be
+ * extremely inefficient.
+ */
+#include <stdio.h>
+#include "khash.h"
+KHASH_MAP_INIT_STR(str, int)
+
+inline void int2str(int c, int base, char *ret)
+{
+	const char *tab = "0123456789abcdef";
+	if (c == 0) ret[0] = '0', ret[1] = 0;
+	else {
+		int l, x, y;
+		char buf[16];
+		for (l = 0, x = c < 0? -c : c; x > 0; x /= base) buf[l++] = tab[x%base];
+		if (c < 0) buf[l++] = '-';
+		for (x = l - 1, y = 0; x >= 0; --x) ret[y++] = buf[x];
+		ret[y] = 0;
+	}
+}
+
+int main(int argc, char *argv[])
+{
+	int i, l, n = 1000, ret;
+	khash_t(str) *h, *h2;
+	khint_t k;
+	h = kh_init(str);
+	h2 = kh_init(str);
+	if (argc > 1) n = atoi(argv[1]);
+	for (i = 0; i < 10000; ++i) {
+		char buf[32];
+		strcpy(buf, "foo_");
+		int2str(i, 10, buf+4);
+		k = kh_put(str, h, strdup(buf), &ret);
+		kh_val(h, k) = i;
+	}
+	for (i = 0; i < n; ++i) {
+		for (k = kh_begin(h); k != kh_end(h); ++k) {
+			if (kh_exist(h, k)) {
+				khint_t k2 = kh_put(str, h2, kh_key(h, k), &ret);
+				if (ret) { // absent
+					kh_key(h2, k2) = strdup(kh_key(h, k));
+					kh_val(h2, k2) = kh_val(h, k);
+				} else kh_val(h2, k2) += kh_val(h, k);
+			}
+		}
+	}
+	k = kh_get(str, h, "foo_1"); printf("%d", kh_val(h, k));
+	k = kh_get(str, h, "foo_9999"); printf(" %d", kh_val(h, k));
+	k = kh_get(str, h2, "foo_1"); printf(" %d", kh_val(h2, k));
+	k = kh_get(str, h2, "foo_9999"); printf(" %d\n", kh_val(h2, k));
+	for (k = kh_begin(h); k != kh_end(h); ++k)
+		if (kh_exist(h, k)) free((char*)kh_key(h, k));
+	for (k = kh_begin(h2); k != kh_end(h2); ++k)
+		if (kh_exist(h2, k)) free((char*)kh_key(h2, k));
+	kh_destroy(str, h);
+	kh_destroy(str, h2);
+	return 0;
+}