From 06e0d48794d9872ef627e15d5edf3bbcb7ad1752 Mon Sep 17 00:00:00 2001
From: Marco Costalba <mcostalba@gmail.com>
Date: Sun, 7 Aug 2011 10:29:47 +0100
Subject: [PATCH 1/1] 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>
---
 src/search.cpp | 38 ++++++++++++++++++++++----------------
 1 file changed, 22 insertions(+), 16 deletions(-)

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);
 
-- 
2.39.2