Increase risk of blunders at low skill levels

According to Heinz's tests current setup is in fact too
strong for weak players. This seems the best according
to his tests.

No functional change.

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

diff --git a/src/search.cpp b/src/search.cpp
index 516f2d051cc503f058d2f541a7d46ef9fcb8800e..20dbd23f796763c199f4e6d0fb027dd03254f00d 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -596,7 +596,7 @@ namespace {
     SearchStack ss[PLY_MAX_PLUS_2];
     Value bestValues[PLY_MAX_PLUS_2];
     int bestMoveChanges[PLY_MAX_PLUS_2];
     SearchStack ss[PLY_MAX_PLUS_2];
     Value bestValues[PLY_MAX_PLUS_2];
     int bestMoveChanges[PLY_MAX_PLUS_2];

-    int depth, aspirationDelta, skillSamplingDepth;
+    int depth, aspirationDelta;

     Value value, alpha, beta;
     Move bestMove, easyMove, skillBest, skillPonder;
 
     Value value, alpha, beta;
     Move bestMove, easyMove, skillBest, skillPonder;
 


@@ -605,7 +605,7 @@ namespace {
     TT.new_search();
     H.clear();
     *ponderMove = bestMove = easyMove = skillBest = skillPonder = MOVE_NONE;
     TT.new_search();
     H.clear();
     *ponderMove = bestMove = easyMove = skillBest = skillPonder = MOVE_NONE;

-    depth = aspirationDelta = skillSamplingDepth = 0;
+    depth = aspirationDelta = 0;

     alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
     ss->currentMove = MOVE_NULL; // Hack to skip update_gains()
 
     alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
     ss->currentMove = MOVE_NULL; // Hack to skip update_gains()
 


@@ -622,11 +622,6 @@ namespace {
         return MOVE_NONE;
     }
 
         return MOVE_NONE;
     }
 

-    // Choose a random sampling depth according to SkillLevel so that at low
-    // skills there is an higher risk to pick up a blunder.
-    if (SkillLevelEnabled)
-        skillSamplingDepth = 4 + SkillLevel + (RK.rand<unsigned>() % 4);
-

     // Iterative deepening loop
     while (++depth <= PLY_MAX && (!MaxDepth || depth <= MaxDepth) && !StopRequest)
     {
     // Iterative deepening loop
     while (++depth <= PLY_MAX && (!MaxDepth || depth <= MaxDepth) && !StopRequest)
     {


@@ -690,7 +685,7 @@ namespace {
         bestMoveChanges[depth] = Rml.bestMoveChanges;
 
         // Do we need to pick now the best and the ponder moves ?
         bestMoveChanges[depth] = Rml.bestMoveChanges;
 
         // Do we need to pick now the best and the ponder moves ?

-        if (SkillLevelEnabled && depth == skillSamplingDepth)
+        if (SkillLevelEnabled && depth == 1 + SkillLevel)

             do_skill_level(&skillBest, &skillPonder);
 
         // Send PV line to GUI and to log file
             do_skill_level(&skillBest, &skillPonder);
 
         // Send PV line to GUI and to log file