htable: tools/density

[ccan] / ccan / htable / tools / density.c

diff --git a/ccan/htable/tools/density.c b/ccan/htable/tools/density.c
new file mode 100644 (file)
index 0000000..5f7400b
--- /dev/null
+++ b/ccan/htable/tools/density.c
@@ -0,0 +1,107 @@
+/* Density measurements for hashtables. */
+#include <ccan/err/err.h>
+#include <ccan/htable/htable_type.h>
+#include <ccan/htable/htable.c>
+#include <ccan/hash/hash.h>
+#include <ccan/ptrint/ptrint.h>
+#include <ccan/time/time.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+/* We don't actually hash objects: we put values in as if they were ptrs */
+static uintptr_t key(const ptrint_t *obj)
+{
+       return ptr2int(obj);
+}
+
+static size_t hash_uintptr(uintptr_t key)
+{
+       return hashl(&key, 1, 0);
+}
+
+static bool cmp(const ptrint_t *p, uintptr_t k)
+{
+       return key(p) == k;
+}
+
+HTABLE_DEFINE_TYPE(ptrint_t, key, hash_uintptr, cmp, htable_ptrint);
+
+/* Nanoseconds per operation */
+static size_t normalize(const struct timeabs *start,
+                       const struct timeabs *stop,
+                       unsigned int num)
+{
+       return time_to_nsec(time_divide(time_between(*stop, *start), num));
+}
+
+static size_t average_run(const struct htable_ptrint *ht, size_t count, size_t *longest)
+{
+       size_t i, total = 0;
+
+       *longest = 0;
+       for (i = 0; i < count; i++) {
+               size_t h = hash_uintptr(i + 2);
+               size_t run = 1;
+
+               while (get_raw_ptr(&ht->raw, ht->raw.table[h % ((size_t)1 << ht->raw.bits)]) != int2ptr(i + 2)) {
+                       h++;
+                       run++;
+               }
+               total += run;
+               if (run > *longest)
+                       *longest = run;
+       }
+       return total / count;
+}
+
+int main(int argc, char *argv[])
+{
+       unsigned int i;
+       size_t num;
+       struct timeabs start, stop;
+       struct htable_ptrint ht;
+
+       if (argc != 2)
+               errx(1, "Usage: density <power-of-2-tablesize>");
+
+       num = atoi(argv[1]);
+
+       printf("Total buckets, buckets used, nanoseconds search time per element, avg run, longest run\n");
+       for (i = 1; i <= 99; i++) {
+               uintptr_t j;
+               struct htable_ptrint_iter it;
+               size_t count, avg_run, longest_run;
+               ptrint_t *p;
+
+               htable_ptrint_init_sized(&ht, num * 3 / 4);
+               assert((1 << ht.raw.bits) == num);
+
+               /* Can't put 0 or 1 in the hash table: multiply by a prime. */
+               for (j = 0; j < num * i / 100; j++) {
+                       htable_ptrint_add(&ht, int2ptr(j + 2));
+                       /* stop it from doubling! */
+                       ht.raw.elems = num / 2;
+               }
+               /* Must not have changed! */
+               assert((1 << ht.raw.bits) == num);
+
+               /* Clean cache */
+               count = 0;
+               for (p = htable_ptrint_first(&ht, &it); p; p = htable_ptrint_next(&ht, &it))
+                       count++;
+               assert(count == num * i / 100);
+               start = time_now();
+               for (j = 0; j < count; j++)
+                       assert(htable_ptrint_get(&ht, j + 2));
+               stop = time_now();
+               avg_run = average_run(&ht, count, &longest_run);
+               printf("%zu,%zu,%zu,%zu,%zu\n",
+                      num, count, normalize(&start, &stop, count), avg_run, longest_run);
+               fflush(stdout);
+               htable_ptrint_clear(&ht);
+       }
+
+       return 0;
+}