From: Marco Costalba <mcostalba@gmail.com>
Date: Sat, 9 Mar 2019 12:24:26 +0000 (+0100)
Subject: Revert "Allowing singular extension in mate positions"
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=4d0981fef37c85edfd7a0e713d68a4542d7a6784

Revert "Allowing singular extension in mate positions"

It was causing an assert: value > -VALUE_INFINITE
under some conditions.

See https://github.com/official-stockfish/Stockfish/issues/2036

Bench: 3318033
---

diff --git a/src/search.cpp b/src/search.cpp
index 31ae5377..9165468a 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -914,12 +914,13 @@ moves_loop: // When in check, search starts from here
           &&  move == ttMove
           && !rootNode
           && !excludedMove // Avoid recursive singular search
-          &&  ttValue != VALUE_NONE
+      /*  &&  ttValue != VALUE_NONE Already implicit in the next condition */
+          &&  abs(ttValue) < VALUE_KNOWN_WIN
           && (tte->bound() & BOUND_LOWER)
           &&  tte->depth() >= depth - 3 * ONE_PLY
           &&  pos.legal(move))
       {
-          Value singularBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE);
+          Value singularBeta = ttValue - 2 * depth / ONE_PLY;
           ss->excludedMove = move;
           value = search<NonPV>(pos, ss, singularBeta - 1, singularBeta, depth / 2, cutNode);
           ss->excludedMove = MOVE_NONE;