Update UCI_Elo parameterization

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index d27b21d2cb8b53e3e77a84e4d147bc1415c2cea8..346fd6c3a7ab322c0cdc4eb4f29397cd3b799a28 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -96,7 +96,10 @@ namespace {
   struct Skill {
     Skill(int skill_level, int uci_elo) {
         if (uci_elo)
-            level = std::clamp(std::pow((uci_elo - 1346.6) / 143.4, 1 / 0.806), 0.0, 20.0);
+        {
+            double e = double(uci_elo - 1320) / (3190 - 1320);
+            level = std::clamp((((37.2473 * e - 40.8525) * e + 22.2943) * e - 0.311438), 0.0, 19.0);
+        }
         else
             level = double(skill_level);
     }
@@ -1215,6 +1218,10 @@ moves_loop: // When in check, search starts here
       // Step 18. Full depth search when LMR is skipped. If expected reduction is high, reduce its depth by 1.
       else if (!PvNode || moveCount > 1)
       {
+               // Increase reduction for cut nodes and not ttMove (~1 Elo)
+               if (!ttMove && cutNode)
+                         r += 2;
+
                value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth - (r > 4), !cutNode);
       }
 
@@ -1359,14 +1366,9 @@ moves_loop: // When in check, search starts here
     else if (   (depth >= 5 || PvNode || bestValue < alpha - 65 * depth)
              && !priorCapture)
     {
-        //Assign extra bonus if current node is PvNode or cutNode
-        //or fail low was really bad
-        bool extraBonus =    PvNode
-                          || cutNode;
-
-        bool doubleExtraBonus = extraBonus && bestValue < alpha - 88 * depth;
-
-        update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * (1 + extraBonus + doubleExtraBonus));
+        // Extra bonuses for PV/Cut nodes or bad fail lows
+        int bonus = 1 + (PvNode || cutNode) + (bestValue < alpha - 88 * depth);
+        update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * bonus);
     }
 
     if (PvNode)