search: improve retrieving from transposition table

e0ff · Dec 4, 2023 · 92f0dd1 · 92f0dd1
1 parent fcd8c10
commit 92f0dd1
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Showing 2 changed files with 7 additions and 5 deletions.
diff --git a/internal/search/negamax.go b/internal/search/negamax.go
@@ -152,20 +152,20 @@ func (s *NegamaxSearcher) doSearch(position *chess.Position, alpha int, beta int
 
 	entry, ok := s.ttable.Get(position.Hash())
 	if ok {
-		if entry.Depth >= depth {
+		if entry.Depth >= depth && entry.Hash == position.Hash() && ply != 0 {
 			switch entry.Type {
 			case ExactNode:
 				s.pvlength[ply] = ply + 1
 				s.pvtable[ply][ply] = entry.Move
 				return entry.Score
 			case UpperNode:
-				if entry.Score < alpha {
+				if entry.Score <= alpha {
 					return alpha
 				}
 
 				break
 			case LowerNode:
-				if entry.Score > beta {
+				if entry.Score >= beta {
 					return beta
 				}
 
@@ -253,7 +253,7 @@ func (s *NegamaxSearcher) doSearch(position *chess.Position, alpha int, beta int
 	}
 
 	if !s.stop {
-		entry := NewTableEntry(nodeType, bestMove, bestScore, depth, position.Plies())
+		entry := NewTableEntry(position.Hash(), nodeType, bestMove, bestScore, depth, position.Plies())
 		s.ttable.Insert(position.Hash(), entry)
 	}
 

diff --git a/internal/search/transposition.go b/internal/search/transposition.go
@@ -28,6 +28,7 @@ func (t NodeType) String() string {
 }
 
 type TableEntry struct {
+	Hash  uint64
 	Type  NodeType
 	Move  chess.Move
 	Score int
@@ -46,8 +47,9 @@ const (
 )
 
 // NewTableEntry creates a new TableEntry.
-func NewTableEntry(nodeType NodeType, move chess.Move, score, depth int, age int) TableEntry {
+func NewTableEntry(hash uint64, nodeType NodeType, move chess.Move, score, depth int, age int) TableEntry {
 	return TableEntry{
+		Hash:  hash,
 		Type:  nodeType,
 		Move:  move,
 		Score: score,