From: ianfab <ianfab@users.noreply.github.com>
Date: Sat, 28 Jul 2018 15:22:39 +0000 (+0200)
Subject: Tweak SEE for nCheck and extinction variants
X-Git-Url: http://winboard.nl/cgi-bin?a=commitdiff_plain;h=612334747632a3ff404cb66e8a7bb7d6159577cf;p=fairystockfish.git

Tweak SEE for nCheck and extinction variants

3check STC
LLR: 2.96 (-2.94,2.94) [0.00,10.00]
Total: 131 W: 115 L: 14 D: 2

extinction STC
LLR: 2.97 (-2.94,2.94) [0.00,10.00]
Total: 92 W: 90 L: 1 D: 1
---

diff --git a/src/position.cpp b/src/position.cpp
index 098a681..e4044d6 100644
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -1306,6 +1306,20 @@ bool Position::see_ge(Move m, Value threshold) const {
   Color stm = ~us; // First consider opponent's move
   Value balance;   // Values of the pieces taken by us minus opponent's ones
 
+
+  // nCheck
+  if (max_check_count() && color_of(moved_piece(m)) == sideToMove && gives_check(m))
+      return true;
+
+  // Extinction
+  if (   extinction_value() != VALUE_NONE
+      && piece_on(to)
+      && (   (   extinction_piece_types().find(type_of(piece_on(to))) != extinction_piece_types().end()
+              && pieceCount[piece_on(to)] == 1)
+          || (   extinction_piece_types().find(ALL_PIECES) != extinction_piece_types().end()
+              && count<ALL_PIECES>(~sideToMove) == 1)))
+      return extinction_value() < VALUE_ZERO;
+
   // The opponent may be able to recapture so this is the best result
   // we can hope for.
   balance = PieceValue[MG][piece_on(to)] - threshold;