htable: tools/density

Everyone loves stats: this looks at different levels of table density
and lookup speed.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/ccan/htable/tools/Makefile b/ccan/htable/tools/Makefile
index a2cad59f0c2dd7e2edf17fd290d89c7a0112e522..c8a428a7567ca08458bfe5be6f749ea281c563b6 100644 (file)
--- a/ccan/htable/tools/Makefile
+++ b/ccan/htable/tools/Makefile
@@ -4,9 +4,10 @@ CFLAGS=-Wall -Werror -O3 -I$(CCANDIR)
 
 CCAN_OBJS:=ccan-tal.o ccan-tal-str.o ccan-tal-grab_file.o ccan-take.o ccan-time.o ccan-str.o ccan-noerr.o ccan-list.o
 
-all: speed stringspeed hsearchspeed
+all: speed stringspeed hsearchspeed density
 
 speed: speed.o hash.o $(CCAN_OBJS)
+density: density.o hash.o $(CCAN_OBJS)
 
 speed.o: speed.c ../htable.h ../htable.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;
+}