From a408dc2356fa5efdaa00f59457dac46f8296bf4c Mon Sep 17 00:00:00 2001
From: Daniel Dugovic <dandydand@gmail.com>
Date: Sat, 31 Dec 2016 15:24:44 -0600
Subject: [PATCH] Avoid expensive crazyhouse null-move searches (resolves #148)

---
 src/position.h | 6 ++++--
 src/search.cpp | 7 +++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/position.h b/src/position.h
index 02dfef18ea3..0c355026bea 100644
--- a/src/position.h
+++ b/src/position.h
@@ -634,10 +634,12 @@ inline int Position::count_in_hand(Color c, PieceType pt) const {
 
 inline void Position::add_to_hand(Color c, PieceType pt) {
   pieceCountInHand[c][pt]++;
+  pieceCountInHand[c][ALL_PIECES]++;
 }
 
 inline void Position::remove_from_hand(Color c, PieceType pt) {
   pieceCountInHand[c][pt]--;
+  pieceCountInHand[c][ALL_PIECES]--;
 }
 
 inline bool Position::is_promoted(Square s) const {
@@ -807,13 +809,13 @@ inline void Position::move_piece(Piece pc, Square from, Square to) {
 inline void Position::drop_piece(Piece pc, Square s) {
   assert(pieceCountInHand[color_of(pc)][type_of(pc)]);
   put_piece(pc, s);
-  pieceCountInHand[color_of(pc)][type_of(pc)]--;
+  remove_from_hand(color_of(pc), type_of(pc));
 }
 
 inline void Position::undrop_piece(Piece pc, Square s) {
   remove_piece(pc, s);
   board[s] = NO_PIECE;
-  pieceCountInHand[color_of(pc)][type_of(pc)]++;
+  add_to_hand(color_of(pc), type_of(pc));
   assert(pieceCountInHand[color_of(pc)][type_of(pc)]);
 }
 #endif
diff --git a/src/search.cpp b/src/search.cpp
index 7665bf68159..1789322711e 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -975,7 +975,14 @@ namespace {
     if (   !PvNode
         &&  eval >= beta
         && (ss->staticEval >= beta - 35 * (depth / ONE_PLY - 6) || depth >= 13 * ONE_PLY)
+#ifdef CRAZYHOUSE
+        // Do not bother with null-move search if opponent can drop pieces
+        && (pos.is_house() ? (eval < 2 * VALUE_KNOWN_WIN
+            && !(depth > 4 * ONE_PLY && pos.count_in_hand(~pos.side_to_move(), ALL_PIECES))) :
+            pos.non_pawn_material(pos.side_to_move())))
+#else
         &&  pos.non_pawn_material(pos.side_to_move()))
+#endif
     {
         ss->currentMove = MOVE_NULL;
         ss->counterMoves = nullptr;