From: Marco Costalba <mcostalba@gmail.com>
Date: Wed, 25 Nov 2009 16:16:51 +0000 (+0100)
Subject: Document why we don't use TT to prune in search_pv()
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=6ae30e7cb10cf5b673aa6998d495b1527a43478d;hp=5ea816792175ec53523035673dad703e7be1f662

Document why we don't use TT to prune in search_pv()

From a Joona' s post on talkchess.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
---

diff --git a/src/search.cpp b/src/search.cpp
index 5d803949..0a53225a 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1121,7 +1121,14 @@ namespace {
         return alpha;
 
     // Transposition table lookup. At PV nodes, we don't use the TT for
-    // pruning, but only for move ordering.
+    // pruning, but only for move ordering. This is to avoid problems in
+    // the following areas:
+    //
+    // * Repetition draw detection
+    // * Fifty move rule detection
+    // * Searching for a mate
+    // * Printing of full PV line
+    //
     tte = TT.retrieve(pos.get_key());
     ttMove = (tte ? tte->move() : MOVE_NONE);