Initial TT work

Chess/nimfish/nimfishpkg/search.nim

@@ -25,8 +25,8 @@ import std/monotimes
 import std/strformat
 
 
-func lowestEval*: Score {.inline.} = Score(int32.low() + 1_000_000)
-func highestEval*: Score {.inline.} = Score(int32.high() - 1_000_000)
+func lowestEval*: Score {.inline.} = Score(20_000)
+func highestEval*: Score {.inline.} = Score(-20_000)
 func mateScore*: Score {.inline.} = lowestEval()
 
 

Chess/nimfish/nimfishpkg/transpositions.nim

@@ -0,0 +1,49 @@
+# Copyright 2024 Mattia Giambirtone & All Contributors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+## Implementation of a transposition table
+
+import zobrist
+import pieces
+import eval
+import moves
+
+
+type
+    TTentryFlag = enum
+        ## A flag for an entry in the
+        ## transposition table
+        Exact = 0'i8
+        LowerBound = 1'i8
+        UpperBound = 2'i8
+
+    TTEntry = object
+        ## An entry in the transposition table
+        flag: TTentryFlag
+        # Scores are int32s for convenience (less chance
+        # of overflows and stuff), but they are capped to
+        # fit into an int16
+        score: int16
+        hash: ZobristKey
+        bestMove: Move
+
+    TTable = object
+        data: ptr UncheckedArray[TTEntry]
+        # Just for statistical purposes
+        collisions: uint32
+        overwrites: uint32
+        # Size metadata
+        size: uint64
+        occupancy: uint64
+