adjust TT score for mates & collect PV

znxftw · Dec 22, 2024 · 447c5f2 · 447c5f2
1 parent bce723e
commit 447c5f2
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Showing 4 changed files with 64 additions and 10 deletions.
diff --git a/Rudim.Test/UnitTest/Board/TraversalTest.cs b/Rudim.Test/UnitTest/Board/TraversalTest.cs
@@ -13,10 +13,10 @@ public class TraversalTest
         // This helps keep track if certain optimizations are good enough to make up for the extra time spent
         // Compare time spent with and without the change before updating the keys
         [Theory]
-        [InlineData(Helpers.StartingFEN, 2170912, 7, 8)]
-        [InlineData(Helpers.EndgameFEN, 450006, 36, 9)]
-        [InlineData(Helpers.AdvancedMoveFEN, 4800762, 1750, 8)]
-        [InlineData(Helpers.KiwiPeteFEN, 11787207, -42, 8)]
+        [InlineData(Helpers.StartingFEN, 3513132, 7, 8)]
+        [InlineData(Helpers.EndgameFEN, 782171, 36, 9)]
+        [InlineData(Helpers.AdvancedMoveFEN, 6979392, 1750, 8)]
+        [InlineData(Helpers.KiwiPeteFEN, 15534609, -42, 8)]
         public void ShouldTraverseDeterministically(string position, int expectedNodes, int expectedScore, int depth)
         {
             Global.Reset();

diff --git a/Rudim/Common/TranspositionTable.cs b/Rudim/Common/TranspositionTable.cs
@@ -1,4 +1,6 @@
+using Rudim.Board;
 using System;
+using System.Collections.Generic;
 
 namespace Rudim.Common
 {
@@ -51,6 +53,52 @@ public static void SubmitEntry(ulong hash, int score, int depth, Move bestMove,
                 return;
             Entries[index] = new TranspositionTableEntry { Hash = hash, Score = score, Depth = depth, BestMove = bestMove, Type = entryType };
         }
+
+        public static List<Move> CollectPrincipalVariation(BoardState boardState)
+        {
+            List<Move> pv = new();
+            while (true)
+            {
+                TranspositionTableEntry entry = Entries[boardState.BoardHash & (Capacity - 1)];
+                if (entry == null || entry.Hash != boardState.BoardHash || entry.Type != TranspositionEntryType.Exact)
+                {
+                    break;
+                }
+                pv.Add(entry.BestMove);
+                boardState.MakeMove(entry.BestMove);
+            }
+
+            for (int i = pv.Count - 1; i >= 0; i--)
+            {
+                boardState.UnmakeMove(pv[i]);
+            }
+            return pv;
+        }
+
+        public static int AdjustScore(int score, int ply)
+        {
+            if (!IsCloseToCheckmate(score))
+            {
+                return score;
+            }
+
+            return score + (score > 0 ? +ply :  -ply);
+        }
+
+        public static int RetrieveScore(int score, int ply)
+        {
+            if (!IsCloseToCheckmate(score))
+            {
+                return score;
+            }
+
+            return score + (score > 0 ? -ply : +ply);
+        }
+
+        private static bool IsCloseToCheckmate(int score)
+        {
+            return Constants.MaxCentipawnEval - Math.Abs(score) <= Constants.MaxPly;
+        }
     }
 
     public class TranspositionTableEntry

diff --git a/Rudim/Search/IterativeDeepening.cs b/Rudim/Search/IterativeDeepening.cs
@@ -2,7 +2,9 @@
 using Rudim.CLI;
 using Rudim.Common;
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
+using System.Linq;
 using System.Threading;
 
 namespace Rudim.Search
@@ -37,7 +39,10 @@ public static void Search(BoardState boardState, int depth, CancellationToken ca
 
                 if (debugMode)
                 {
-                    CliClient.WriteLine($"info depth {i} score cp {Score} nodes {nodesTraversed} time {time} nps {nps}");
+                    List<Move> pv = TranspositionTable.CollectPrincipalVariation(boardState);
+                    string pvString = string.Join(' ', pv.Select(move =>
+                        move.Source.ToString() + move.Target.ToString() + move.GetPromotionChar()));
+                    CliClient.WriteLine($"info depth {i} score cp {Score} nodes {nodesTraversed} time {time} nps {nps} pv {pvString}");
                 }
             }
         }

diff --git a/Rudim/Search/Negamax.cs b/Rudim/Search/Negamax.cs
@@ -28,11 +28,14 @@ public static int Search(BoardState boardState, int depth, CancellationToken can
 
         private static int Search(BoardState boardState, int depth, int alpha, int beta, CancellationToken cancellationToken)
         {
+            int ply = _searchDepth - depth;
+            Nodes++;
+
             (bool hasValue, int ttScore, Move bestEvaluation) = TranspositionTable.GetEntry(boardState.BoardHash, alpha, beta, depth);
             if (hasValue)
             {
                 BestMove = bestEvaluation;
-                return ttScore;
+                return TranspositionTable.RetrieveScore(ttScore, ply);
             }
 
             if (boardState.IsDraw())
@@ -42,10 +45,8 @@ private static int Search(BoardState boardState, int depth, int alpha, int beta,
                 return Quiescence.Search(boardState, alpha, beta, cancellationToken);
 
             int originalAlpha = alpha;
-            int ply = _searchDepth - depth;
             bool foundPv = false;
             TranspositionEntryType entryType = TranspositionEntryType.Alpha;
-            Nodes++;
 
             boardState.GenerateMoves();
             PopulateMoveScores(boardState, ply);
@@ -70,7 +71,7 @@ private static int Search(BoardState boardState, int depth, int alpha, int beta,
                 boardState.UnmakeMove(move);
                 if (score >= beta)
                 {
-                    TranspositionTable.SubmitEntry(boardState.BoardHash, beta, depth, move, TranspositionEntryType.Beta);
+                    TranspositionTable.SubmitEntry(boardState.BoardHash, TranspositionTable.AdjustScore(beta, ply), depth, move, TranspositionEntryType.Beta);
                     return BetaCutoff(beta, move, ply);
                 }
                 if (score > alpha)
@@ -90,7 +91,7 @@ private static int Search(BoardState boardState, int depth, int alpha, int beta,
             if (alpha != originalAlpha)
                 BestMove = bestEvaluation;
 
-            TranspositionTable.SubmitEntry(boardState.BoardHash, alpha, depth, bestEvaluation, entryType);
+            TranspositionTable.SubmitEntry(boardState.BoardHash, TranspositionTable.AdjustScore(alpha, ply), depth, bestEvaluation, entryType);
 
             return alpha;
         }