Prune bad captures in QSearch

src/Lynx/EvaluationConstants.cs

@@ -336,6 +336,7 @@ static EvaluationConstants()
 
     public const int ThirdKillerMoveValue = 131_072;
 
+    // Revisit bad capture pruning in NegaMax.cs if order changes and promos aren't the lowest before bad captures
     public const int PromotionMoveScoreValue = 65_536;
 
     public const int BadCaptureMoveBaseScoreValue = 32_768;

src/Lynx/Search/NegaMax.cs

@@ -1,4 +1,5 @@
 using Lynx.Model;
+using System.Transactions;
 
 namespace Lynx;
 
@@ -452,6 +453,12 @@ public int QuiescenceSearch(int ply, int alpha, int beta)
 
             var move = pseudoLegalMoves[i];
 
+            // Prune bad captures
+            if (scores[i] < EvaluationConstants.PromotionMoveScoreValue && scores[i] >= EvaluationConstants.BadCaptureMoveBaseScoreValue)
+            {
+                continue;
+            }
+
             var gameState = position.MakeMove(move);
             if (!position.WasProduceByAValidMove())
             {

tests/Lynx.Test/EvaluationConstantsTest.cs

@@ -172,6 +172,25 @@ public void ThirdKillerMoveValueConstant()
         Assert.Greater(ThirdKillerMoveValue, default);
     }
 
+    [Test]
+    public void PromotionMoveValueConstant()
+    {
+        var maxMVVLVAMoveValue = int.MinValue;
+
+        for (int s = (int)Piece.P; s <= (int)Piece.r; ++s)
+        {
+            for (int t = (int)Piece.P; t <= (int)Piece.r; ++t)
+            {
+                if (MostValueableVictimLeastValuableAttacker[s, t] > maxMVVLVAMoveValue)
+                {
+                    maxMVVLVAMoveValue = MostValueableVictimLeastValuableAttacker[s, t];
+                }
+            }
+        }
+
+        Assert.Less(BadCaptureMoveBaseScoreValue + maxMVVLVAMoveValue, PromotionMoveScoreValue);
+    }
+
     /// <summary>
     /// Avoids drawish evals that can lead the GUI to declare a draw
     /// or negative ones that can lead it to resign