From: Marco Costalba <mcostalba@gmail.com>
Date: Tue, 28 Jul 2015 10:53:13 +0000 (+0200)
Subject: Simplify IID depth formula
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=68d61b80c60a81055a2ffb2e251a237b979e9b31

Simplify IID depth formula

Restore original formula messed up during
half-ply removal.

STC
LLR: 4.11 (-2.94,2.94) [-3.00,1.00]
Total: 21349 W: 4091 L: 3909 D: 13349

LTC
LLR: 5.42 (-2.94,2.94) [-3.00,1.00]
Total: 52819 W: 8321 L: 8122 D: 36376

bench: 8040572
---

diff --git a/src/search.cpp b/src/search.cpp
index 3ac52f8c..57a55176 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -769,9 +769,9 @@ namespace {
         && !ttMove
         && (PvNode || ss->staticEval + 256 >= beta))
     {
-        Depth d = 2 * (depth - 2 * ONE_PLY) - (PvNode ? DEPTH_ZERO : depth / 2);
+        Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4);
         ss->skipEarlyPruning = true;
-        search<PvNode ? PV : NonPV, false>(pos, ss, alpha, beta, d / 2, true);
+        search<PvNode ? PV : NonPV, false>(pos, ss, alpha, beta, d, true);
         ss->skipEarlyPruning = false;
 
         tte = TT.probe(posKey, ttHit);
@@ -821,13 +821,11 @@ moves_loop: // When in check and at SpNode search starts from here
           if (!pos.legal(move, ci.pinned))
               continue;
 
-          moveCount = ++splitPoint->moveCount;
+          ss->moveCount = moveCount = ++splitPoint->moveCount;
           splitPoint->spinlock.release();
       }
       else
-          ++moveCount;
-      
-      ss->moveCount = moveCount;
+          ss->moveCount = ++moveCount;
 
       if (RootNode)
       {
@@ -935,8 +933,7 @@ moves_loop: // When in check and at SpNode search starts from here
       // Check for legality just before making the move
       if (!RootNode && !SpNode && !pos.legal(move, ci.pinned))
       {
-          moveCount--;
-          ss->moveCount = moveCount;
+          ss->moveCount = --moveCount;
           continue;
       }
 
@@ -1429,7 +1426,7 @@ moves_loop: // When in check and at SpNode search starts from here
     }
 
     // Extra penalty for PV move in previous ply when it gets refuted
-    if (is_ok((ss-2)->currentMove) && (ss-1)->moveCount==1 && !pos.captured_piece_type())
+    if (is_ok((ss-2)->currentMove) && (ss-1)->moveCount == 1 && !pos.captured_piece_type())
     {
         Square prevPrevSq = to_sq((ss-2)->currentMove);
         HistoryStats& ttMoveCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq];