Retire EasyMoveMargin

Use a value related to PawnValue instead.

This is a different patch from previous one because
could affect game play and skill levels, although
in a mostly unmeasurable way. Indeed thresold has
been raised so easy move is a bit harder to trigger
and skill level is a bit more prone to blunders.

No functional change.

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

diff --git a/src/search.cpp b/src/search.cpp
index e44324f75802677e47b9a55164f00bcf82f30fb3..31edcc2f8845e37774cfb915163bccdcd2cc3577 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -88,10 +88,6 @@ namespace {
     return (Depth) Reductions[PvNode][std::min(int(d) / ONE_PLY, 63)][std::min(mn, 63)];
   }
 
     return (Depth) Reductions[PvNode][std::min(int(d) / ONE_PLY, 63)][std::min(mn, 63)];
   }
 

-  // Easy move margin. An easy move candidate must be at least this much better
-  // than the second best move.
-  const Value EasyMoveMargin = Value(0x150);
-

   // This is the minimum interval in msec between two check_time() calls
   const int TimerResolution = 5;
 
   // This is the minimum interval in msec between two check_time() calls
   const int TimerResolution = 5;
 


@@ -450,7 +446,7 @@ namespace {
                 && (   (bestMoveNeverChanged &&  pos.captured_piece_type())
                     || Time::now() - SearchTime > (TimeMgr.available_time() * 40) / 100))
             {
                 && (   (bestMoveNeverChanged &&  pos.captured_piece_type())
                     || Time::now() - SearchTime > (TimeMgr.available_time() * 40) / 100))
             {

-                Value rBeta = bestValue - EasyMoveMargin;
+                Value rBeta = bestValue - 2 * PawnValueMg;

                 (ss+1)->excludedMove = RootMoves[0].pv[0];
                 (ss+1)->skipNullMove = true;
                 Value v = search<NonPV>(pos, ss+1, rBeta - 1, rBeta, (depth - 3) * ONE_PLY);
                 (ss+1)->excludedMove = RootMoves[0].pv[0];
                 (ss+1)->skipNullMove = true;
                 Value v = search<NonPV>(pos, ss+1, rBeta - 1, rBeta, (depth - 3) * ONE_PLY);


@@ -1494,7 +1490,7 @@ split_point_start: // At split points actual search starts from here
         int s = RootMoves[i].score;
 
         // Don't allow crazy blunders even at very low skills
         int s = RootMoves[i].score;
 
         // Don't allow crazy blunders even at very low skills

-        if (i > 0 && RootMoves[i-1].score > s + EasyMoveMargin)
+        if (i > 0 && RootMoves[i-1].score > s + 2 * PawnValueMg)

             break;
 
         // This is our magic formula
             break;
 
         // This is our magic formula