From a47a7dadeb505bbd8336effe573a0ea18816021e Mon Sep 17 00:00:00 2001 From: Marco Costalba Date: Sun, 11 Jul 2010 07:52:05 +0100 Subject: [PATCH] Fix (zugzwang) verification to be shallower then null search Currently starting from depth 12*OnePly on we have a verification search deeper then the null search. Note that, although reduction is R we start from one ply less then null search, so actually we reach a depth that is OnePly shallower then null search. After 1130 games at 1'+0 on QUAD Mod vs Orig +202 =756 -172 +9 ELO Signed-off-by: Marco Costalba --- src/search.cpp | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/src/search.cpp b/src/search.cpp index e38f4021..0ef2f600 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -1203,12 +1203,12 @@ namespace { if (nullValue >= value_mate_in(PLY_MAX)) nullValue = beta; - // Do zugzwang verification search at high depths if (depth < 6 * OnePly) return nullValue; + // Do verification search at high depths ss->skipNullMove = true; - Value v = search(pos, ss, alpha, beta, depth-5*OnePly, ply); + Value v = search(pos, ss, alpha, beta, depth-R*OnePly, ply); ss->skipNullMove = false; if (v >= beta) -- 2.39.2