From: Stefan Geschwentner <stgeschwentner@gmail.com>
Date: Sun, 28 Aug 2016 10:39:49 +0000 (+0200)
Subject: Tweak probcut threshold
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=6aa9308f08bc76b0e3615dde65de7782a6761fa3;hp=b4f6728e610848b202cee47af28fa3bb0a251e3c;ds=sidebyside

Tweak probcut threshold

Use better threshold for capture move generation.

STC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 23265 W: 4415 L: 4188 D: 14662

LTC:
LLR: 2.95 (-2.94,2.94) [0.00,4.00]
Total: 36618 W: 5083 L: 4836 D: 26699

bench: 7030088
---

diff --git a/src/search.cpp b/src/search.cpp
index ff31e036..cf7e411d 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -788,9 +788,8 @@ namespace {
     }
 
     // Step 9. ProbCut (skipped when in check)
-    // If we have a very good capture (i.e. SEE > seeValues[captured_piece_type])
-    // and a reduced search returns a value much above beta, we can (almost)
-    // safely prune the previous move.
+    // If we have a good enough capture and a reduced search returns a value
+    // much above beta, we can (almost) safely prune the previous move.
     if (   !PvNode
         &&  depth >= 5 * ONE_PLY
         &&  abs(beta) < VALUE_MATE_IN_MAX_PLY)
@@ -802,7 +801,7 @@ namespace {
         assert((ss-1)->currentMove != MOVE_NONE);
         assert((ss-1)->currentMove != MOVE_NULL);
 
-        MovePicker mp(pos, ttMove, PieceValue[MG][pos.captured_piece_type()]);
+        MovePicker mp(pos, ttMove, rbeta - ss->staticEval);
 
         while ((move = mp.next_move()) != MOVE_NONE)
             if (pos.legal(move))