From: Marco Costalba <mcostalba@gmail.com>
Date: Sat, 3 Sep 2016 06:19:17 +0000 (+0200)
Subject: Fix syzygy with partial TB
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=c5828c4eba9e4e3f448e8370f24804da719a5120;hp=d37dfe9ae41de722eccd50aee39fb5eb59811bc2

Fix syzygy with partial TB

In case we have installed a not complete set of 6-men tables and
there is 6 piece position on board, but no corresponding
tablebase engine is not using any syzygy at all.

Reported by Jouni Uski, fix by Peter Österlund,
confirmed as a bug by Ronald de Man.

bench: 7591630
---

diff --git a/src/search.cpp b/src/search.cpp
index c12f0862..fe450a4e 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1641,7 +1641,7 @@ void Tablebases::filter_root_moves(Position& pos, Search::RootMoves& rootMoves)
         RootInTB = root_probe_wdl(pos, rootMoves, TB::Score);
 
         // Only probe during search if winning
-        if (TB::Score <= VALUE_DRAW)
+        if (RootInTB && TB::Score <= VALUE_DRAW)
             Cardinality = 0;
     }