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refactor(official-bots): use java.util.Random in PolyglotBook
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scala.util.Random delegates to a shared global java.util.Random, a
contention point across concurrent bot games. Use a per-book
java.util.Random instance instead.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Janis Eccarius
2026-06-23 23:34:38 +02:00
parent 4a50db0721
commit f8ca95af3c
1 changed files with 4 additions and 2 deletions
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modules/official-bots/src/main/scala/de/nowchess/bot/util/PolyglotBook.scala
+4 -2
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@@ -5,8 +5,8 @@ import de.nowchess.api.game.GameContext
import de.nowchess.api.move.{Move, MoveType, PromotionPiece} import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
import java.io.{DataInputStream, FileInputStream, InputStream} import java.io.{DataInputStream, FileInputStream, InputStream}
import java.util.Random
import scala.collection.mutable import scala.collection.mutable
import scala.util.Random
/** Reads a Polyglot opening book (.bin file) and probes it for moves. /** Reads a Polyglot opening book (.bin file) and probes it for moves.
* *
@@ -18,6 +18,8 @@ import scala.util.Random
*/ */
final class PolyglotBook private (entries: Map[Long, Vector[BookEntry]]): final class PolyglotBook private (entries: Map[Long, Vector[BookEntry]]):
private val rng = Random()
/** Probe the book for a move in the given position. Returns a weighted random move, or None if not in book. */ /** Probe the book for a move in the given position. Returns a weighted random move, or None if not in book. */
def probe(context: GameContext): Option[Move] = def probe(context: GameContext): Option[Move] =
val hash = PolyglotHash.hash(context) val hash = PolyglotHash.hash(context)
@@ -93,7 +95,7 @@ final class PolyglotBook private (entries: Map[Long, Vector[BookEntry]]):
if entries.length == 1 then entries.head if entries.length == 1 then entries.head
else else
val totalWeight = entries.map(_.weight).sum val totalWeight = entries.map(_.weight).sum
val pick = Random.nextInt(totalWeight.max(1)) // NOSONAR val pick = rng.nextInt(totalWeight.max(1)) // NOSONAR
@scala.annotation.tailrec @scala.annotation.tailrec
def select(remaining: Int, idx: Int): BookEntry = def select(remaining: Int, idx: Int): BookEntry =