From: Fabian Fichter <ianfab@users.noreply.github.com>
Date: Mon, 1 Feb 2021 17:57:28 +0000 (+0100)
Subject: Tweak futility pruning for racing kings
X-Git-Url: http://winboard.nl/cgi-bin?a=commitdiff_plain;h=573241e9cb9e0eb309b5ee40bccf043c07c5734c;p=fairystockfish.git

Tweak futility pruning for racing kings

racingkings STC
LLR: 2.96 (-2.94,2.94) [0.00,10.00]
Total: 1610 W: 544 L: 450 D: 616
http://www.variantfishtest.org:6543/tests/view/6016cb9b6e23db669974e6ce

racingkings LTC
LLR: 2.96 (-2.94,2.94) [0.00,10.00]
Total: 3787 W: 1113 L: 998 D: 1676
http://www.variantfishtest.org:6543/tests/view/6016d1186e23db669974e6d4
---

diff --git a/src/search.cpp b/src/search.cpp
index 50c490b..8b67407 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -910,8 +910,7 @@ namespace {
     // Step 7. Futility pruning: child node (~50 Elo)
     if (   !PvNode
         &&  depth < 9
-        && !(pos.capture_the_flag_piece() && !pos.checking_permitted())
-        &&  eval - futility_margin(depth, improving) * (1 + pos.check_counting() + 2 * pos.must_capture() + pos.extinction_single_piece()) >= beta
+        &&  eval - futility_margin(depth, improving) * (1 + pos.check_counting() + 2 * pos.must_capture() + pos.extinction_single_piece() + !pos.checking_permitted()) >= beta
         &&  eval < VALUE_KNOWN_WIN) // Do not return unproven wins
         return eval;