50-moves rule improvement for transposition table

[stockfish] / src / tt.cpp

diff --git a/src/tt.cpp b/src/tt.cpp
index 6121b3ad771b24bd40410e8e5f6bff6004fdccc7..0b4a59de55915962e7ed9409ae462be2556366f3 100644 (file)
--- a/src/tt.cpp
+++ b/src/tt.cpp
@@ -2,7 +2,7 @@
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
   Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
-  Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+  Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
 
   Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -35,24 +35,22 @@ TranspositionTable TT; // Our global transposition table
 
 void TTEntry::save(Key k, Value v, bool pv, Bound b, Depth d, Move m, Value ev) {
 
-  assert(d / ONE_PLY * ONE_PLY == d);
-
   // Preserve any existing move for the same position
   if (m || (k >> 48) != key16)
       move16 = (uint16_t)m;
 
   // Overwrite less valuable entries
   if (  (k >> 48) != key16
-      ||(d - DEPTH_OFFSET) / ONE_PLY > depth8 - 4
+      || d - DEPTH_OFFSET > depth8 - 4
       || b == BOUND_EXACT)
   {
-      assert((d - DEPTH_OFFSET) / ONE_PLY >= 0);
+      assert(d >= DEPTH_OFFSET);
 
       key16     = (uint16_t)(k >> 48);
       value16   = (int16_t)v;
       eval16    = (int16_t)ev;
       genBound8 = (uint8_t)(TT.generation8 | uint8_t(pv) << 2 | b);
-      depth8    = (uint8_t)((d - DEPTH_OFFSET) / ONE_PLY);
+      depth8    = (uint8_t)(d - DEPTH_OFFSET);
   }
 }