From: Rusty Russell <rusty@rustcorp.com.au>
Date: Sun, 15 Mar 2015 05:37:26 +0000 (+1030)
Subject: invbloom: reduce hash count to 3.
X-Git-Url: https://git.ozlabs.org/?a=commitdiff_plain;h=eaab3d3e5cef9a612e688cf2b0d099277ade145a;p=ccan

invbloom: reduce hash count to 3.

Kalle shows the superiority of 3 (as does the paper for > 50 buckets).

https://github.com/kallerosenbaum/bitcoin-iblt/wiki/Diff-count-VS-failure-probability

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

diff --git a/ccan/invbloom/invbloom.c b/ccan/invbloom/invbloom.c
index 08d83c88..bda23462 100644
--- a/ccan/invbloom/invbloom.c
+++ b/ccan/invbloom/invbloom.c
@@ -10,7 +10,7 @@
 
 	Eppstein, David, et al. "What's the difference?: efficient set reconciliation without prior context." ACM SIGCOMM Computer Communication Review. Vol. 41. No. 4. ACM, 2011. http://conferences.sigcomm.org/sigcomm/2011/papers/sigcomm/p218.pdf
 */
-#define NUM_HASHES 4
+#define NUM_HASHES 3
 
 struct invbloom *invbloom_new_(const tal_t *ctx,
 			       size_t id_size,