From: Fabian Fichter <ianfab@users.noreply.github.com>
Date: Sat, 27 Feb 2021 23:20:07 +0000 (+0100)
Subject: Tweak singular extension for horde
X-Git-Url: http://winboard.nl/cgi-bin?a=commitdiff_plain;h=49759288ba831c8716ce771f56a72b5a72eecf84;p=fairystockfish.git

Tweak singular extension for horde

horde STC
LLR: -2.95 (-2.94,2.94) [0.00,10.00]
Total: 4108 W: 2008 L: 2050 D: 50
http://www.variantfishtest.org:6543/tests/view/60291c396e23db669974e90c

horde LTC
LLR: 2.95 (-2.94,2.94) [0.00,10.00]
Total: 9687 W: 4917 L: 4676 D: 94
http://www.variantfishtest.org:6543/tests/view/6029a4e46e23db669974e910

horde VLTC
LLR: 2.97 (-2.94,2.94) [0.00,10.00]
Total: 11750 W: 5938 L: 5667 D: 145
http://www.variantfishtest.org:6543/tests/view/602e57606e23db669974e923
---

diff --git a/src/search.cpp b/src/search.cpp
index 0333a67..abaed2d 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1168,7 +1168,7 @@ moves_loop: // When in check, search starts from here
       // then that move is singular and should be extended. To verify this we do
       // a reduced search on all the other moves but the ttMove and if the
       // result is lower than ttValue minus a margin, then we will extend the ttMove.
-      if (    depth >= 7
+      if (    depth >= 7 - 2 * (pos.count<KING>() == 1)
           &&  move == ttMove
           && !rootNode
           && !excludedMove // Avoid recursive singular search