The benchmark for PH prints expected collisions and collision rate.

src/tests/bench/bench_ph.c

@@ -322,6 +322,10 @@ main(int argc, char *argv[])
 	printf("Stats computed in %lu ns\n", tdiff(&before, &after));
 	printf("%lu buckets\n", stats.buckets);
 	printf("%lu collisions\n", stats.collisions);
+	printf("%lu expected collisions\n",
+	       ((uint64_t)n * (uint64_t)(n - 1)) / (stats.buckets * 2));
+	printf("%.3f collision rate\n",
+	       (double)stats.collisions / (double)stats.buckets);
 	printf("%lu key vector length\n", stats.klen);
 	printf("%lu min string length\n", stats.minlen);
 	printf("%lu max string length\n", stats.maxlen);