Further push singular extension

Extend for an extra half-ply in case the node is (probably)
going to fail high. In this case the added overhead is limited.

A novelity is the way this patch has been tested: Always in
self-play but with a much longer TC to allow the singular
extension to fully kick in and also (my impression) to have
less noisy results.

Ater 1015 games on my QUAD at 60"+0.05
Mod vs Orig 173 - 150 - 692 ELO +8

diff --git a/src/search.cpp b/src/search.cpp
index abb5116d2cfe3114bfdd74f7c7c48c3161033c5d..163df7b4ec4b6f4f017fbe13318a0320a820c15e 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -863,7 +863,7 @@ split_point_start: // At split points actual search starts from here
           ss->excludedMove = MOVE_NONE;
 
           if (value < rBeta)
-              ext = ONE_PLY;
+              ext = rBeta >= beta ? ONE_PLY + ONE_PLY / 2 : ONE_PLY;
       }
 
       // Update current move (this must be done after singular extension search)