Less aggressive null move dynamic reduction

In null move search do not jump directly in
qsearch() from depth(4*OnePly), but only
from depth(3*OnePly).

After 999 games at 1+0: +248 -224 =527 +8ELO

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

diff --git a/src/search.cpp b/src/search.cpp
index f18f2f2f65035a9c3740d92b551707e4030e8bfd..e7c4e6ca2c04d4d1b9008125dfacc68633b1e103 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1199,7 +1199,7 @@ namespace {
 
         StateInfo st;
         pos.do_null_move(st);
 
         StateInfo st;
         pos.do_null_move(st);

-        int R = (depth >= 4 * OnePly ? 4 : 3); // Null move dynamic reduction
+        int R = (depth >= 5 * OnePly ? 4 : 3); // Null move dynamic reduction

 
         Value nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);
 
 
         Value nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);