Razor again at depth one

Some time ago it was found by Marco Costalba that it's better
to disable razoring at depth one, because given the very low
evaluation of the node, futility pruning would already do
the job at very low cost and avoiding missing important moves.

Now enable razoring there again, but only when our quickly evaluated
material advantage is more than a rook. The idea is to try razoring
only when it's extremely likely that it will succeed.

Extreme lightning speed test show promising result:
Orig - Mod: +1285 =1495 -1348

This needs to be tested with longer time controls though.

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

diff --git a/src/search.cpp b/src/search.cpp
index a3912603b5af90ea0e60d69293f6d884b0946fc1..5ccc72c890cb263dd40dadd102bf0f8e248493ae 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -193,8 +193,8 @@ namespace {
               //remaining depth:  1 ply         1.5 ply       2 ply         2.5 ply       3 ply         3.5 ply
   const Value RazorMargins[6] = { Value(0x180), Value(0x300), Value(0x300), Value(0x3C0), Value(0x3C0), Value(0x3C0) };
 
-               //remaining depth:     1 ply            1.5 ply       2 ply         2.5 ply       3 ply         3.5 ply
-  const Value RazorApprMargins[6] = { Value(0x100000), Value(0x300), Value(0x300), Value(0x300), Value(0x300), Value(0x300) };
+               //remaining depth:     1 ply         1.5 ply       2 ply         2.5 ply       3 ply         3.5 ply
+  const Value RazorApprMargins[6] = { Value(0x520), Value(0x300), Value(0x300), Value(0x300), Value(0x300), Value(0x300) };
 
   // Last seconds noise filtering (LSN)
   bool UseLSNFiltering;