Use quiet ttMove in qsearch() (7962287)

Daniel Jose reported that it was an elo gain in his engine:
http://www.talkchess.com/forum/viewtopic.php?t=54290

STC: Hash=16
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 33067 W: 6670 L: 6571 D: 19826

LTC: Hash=64
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 41181 W: 7008 L: 6920 D: 27253

And another one to verify no regression with hash pressure:

STC: Hash=4
LLR: 2.96 (-2.94,2.94) [-4.00,0.00]
Total: 25085 W: 5059 L: 4991 D: 15035

Verified that qsearch does not explode after this patch (recapture threshold).

Bench 7962287

Resolves #112

diff --git a/src/movepick.cpp b/src/movepick.cpp
index 84f26dbf7835c08a2794313aad91560d4e6f3991..b5727f109fbcfd8aec263245a9cf944e3f9310a9 100644 (file)
--- a/src/movepick.cpp
+++ b/src/movepick.cpp
@@ -103,15 +103,8 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const HistoryStats&
       stage = QSEARCH_0;
 
   else if (d > DEPTH_QS_RECAPTURES)
       stage = QSEARCH_0;
 
   else if (d > DEPTH_QS_RECAPTURES)

-  {

       stage = QSEARCH_1;
 
       stage = QSEARCH_1;
 

-      // Skip TT move if is not a capture or a promotion. This avoids qsearch
-      // tree explosion due to a possible perpetual check or similar rare cases
-      // when TT table is full.
-      if (ttm && !pos.capture_or_promotion(ttm))
-          ttm = MOVE_NONE;
-  }

   else
   {
       stage = RECAPTURE;
   else
   {
       stage = RECAPTURE;