From: Fabian Fichter <ianfab@users.noreply.github.com>
Date: Mon, 22 Jun 2020 16:05:38 +0000 (+0200)
Subject: Increase futility margin for losing chess
X-Git-Url: http://winboard.nl/cgi-bin?a=commitdiff_plain;h=f712f6f2d455ebe570e406edc369d332d5d655ab;p=fairystockfish.git

Increase futility margin for losing chess

giveaway STC
LLR: 2.96 (-2.94,2.94) [0.00,10.00]
Total: 3110 W: 1188 L: 1066 D: 856
http://www.variantfishtest.org:6543/tests/view/5eed135b6e23db104fb88be8

giveaway LTC
LLR: 2.97 (-2.94,2.94) [0.00,10.00]
Total: 2975 W: 1096 L: 978 D: 901
http://www.variantfishtest.org:6543/tests/view/5eee59f46e23db104fb88c32

losers STC
LLR: 2.96 (-2.94,2.94) [0.00,10.00]
Total: 1118 W: 548 L: 440 D: 130
http://www.variantfishtest.org:6543/tests/view/5eee1cb16e23db104fb88c28

losers LTC
LLR: 2.95 (-2.94,2.94) [0.00,10.00]
Total: 2471 W: 1145 L: 1019 D: 307
http://www.variantfishtest.org:6543/tests/view/5eee2b5c6e23db104fb88c2c
---

diff --git a/src/search.cpp b/src/search.cpp
index 93ff0a1..274c385 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -908,7 +908,7 @@ namespace {
         && !(   pos.extinction_value() == -VALUE_MATE
              && pos.extinction_piece_types().find(ALL_PIECES) == pos.extinction_piece_types().end())
         && !(pos.capture_the_flag_piece() && !pos.checking_permitted())
-        &&  eval - futility_margin(depth, improving) * (1 + pos.check_counting()) >= beta
+        &&  eval - futility_margin(depth, improving) * (1 + pos.check_counting() + 2 * pos.must_capture()) >= beta
         &&  eval < VALUE_KNOWN_WIN) // Do not return unproven wins
         return eval;