From: Marco Costalba <mcostalba@gmail.com>
Date: Sun, 7 Aug 2011 09:29:47 +0000 (+0100)
Subject: Sync search() and qsearch() alpha update
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=06e0d48794d9872ef627e15d5edf3bbcb7ad1752;hp=4a71c862702c05b3c56e902f4675fdf68041710b

Sync search() and qsearch() alpha update

Change qsearch() to reflect alpha update logic
of search().

To be consistent changed also moves loop condition and
futility pruning condition.

No regression after 5072 games at TC 10"+0.1

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

diff --git a/src/search.cpp b/src/search.cpp
index b39bc176..933b4030 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -712,7 +712,7 @@ namespace {
     Depth ext, newDepth;
     ValueType vt;
     Value bestValue, value, oldAlpha;
-    Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
+    Value refinedValue, nullValue, futilityBase, futilityValue;
     bool isPvMove, inCheck, singularExtensionNode, givesCheck, captureOrPromotion, dangerous;
     int moveCount = 0, playedMoveCount = 0;
     Thread& thread = Threads[pos.thread()];
@@ -1070,19 +1070,19 @@ split_point_start: // At split points actual search starts from here
           // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
           // but fixing this made program slightly weaker.
           Depth predictedDepth = newDepth - reduction<PvNode>(depth, moveCount);
-          futilityValueScaled =  futilityBase + futility_margin(predictedDepth, moveCount)
-                               + H.gain(pos.piece_on(move_from(move)), move_to(move));
+          futilityValue =  futilityBase + futility_margin(predictedDepth, moveCount)
+                         + H.gain(pos.piece_on(move_from(move)), move_to(move));
 
-          if (futilityValueScaled < beta)
+          if (futilityValue < beta)
           {
               if (SpNode)
               {
                   lock_grab(&(sp->lock));
-                  if (futilityValueScaled > sp->bestValue)
-                      sp->bestValue = bestValue = futilityValueScaled;
+                  if (futilityValue > sp->bestValue)
+                      sp->bestValue = bestValue = futilityValue;
               }
-              else if (futilityValueScaled > bestValue)
-                  bestValue = futilityValueScaled;
+              else if (futilityValue > bestValue)
+                  bestValue = futilityValue;
 
               continue;
           }
@@ -1298,6 +1298,7 @@ split_point_start: // At split points actual search starts from here
     bool inCheck, enoughMaterial, givesCheck, evasionPrunable;
     const TTEntry* tte;
     Depth ttDepth;
+    ValueType vt;
     Value oldAlpha = alpha;
 
     ss->bestMove = ss->currentMove = MOVE_NONE;
@@ -1368,7 +1369,7 @@ split_point_start: // At split points actual search starts from here
     CheckInfo ci(pos);
 
     // Loop through the moves until no moves remain or a beta cutoff occurs
-    while (   alpha < beta
+    while (   bestValue < beta
            && (move = mp.get_next_move()) != MOVE_NONE)
     {
       assert(move_is_ok(move));
@@ -1388,10 +1389,11 @@ split_point_start: // At split points actual search starts from here
                          + piece_value_endgame(pos.piece_on(move_to(move)))
                          + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
 
-          if (futilityValue < alpha)
+          if (futilityValue < beta)
           {
               if (futilityValue > bestValue)
                   bestValue = futilityValue;
+
               continue;
           }
 
@@ -1450,11 +1452,12 @@ split_point_start: // At split points actual search starts from here
       if (value > bestValue)
       {
           bestValue = value;
-          if (value > alpha)
-          {
+          ss->bestMove = move;
+
+          if (   PvNode
+              && value > alpha
+              && value < beta) // We want always alpha < beta
               alpha = value;
-              ss->bestMove = move;
-          }
        }
     }
 
@@ -1464,8 +1467,11 @@ split_point_start: // At split points actual search starts from here
         return value_mated_in(ss->ply);
 
     // Update transposition table
-    ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
-    TT.store(pos.get_key(), value_to_tt(bestValue, ss->ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
+    move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
+    vt   = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
+         : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
+
+    TT.store(pos.get_key(), value_to_tt(bestValue, ss->ply), vt, ttDepth, move, ss->eval, evalMargin);
 
     assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);