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fix(official-bots): use ThreadLocalRandom in PolyglotBook for native image
Build & Test (NowChessSystems) TeamCity build finished
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A stored java.util.Random field is reachable from BotController's static
openingBook, so GraalVM baked it into the image heap and aborted the
native build (Random in image heap has a cached seed). Use
ThreadLocalRandom.current() at call time instead — no stored instance,
nothing in the image heap, still thread-safe.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Janis Eccarius
2026-06-23 23:42:15 +02:00
parent f8ca95af3c
commit 1b30c3be39
1 changed files with 2 additions and 4 deletions
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modules/official-bots/src/main/scala/de/nowchess/bot/util/PolyglotBook.scala
+2 -4
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@@ -5,7 +5,7 @@ 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 java.util.concurrent.ThreadLocalRandom
import scala.collection.mutable import scala.collection.mutable
/** Reads a Polyglot opening book (.bin file) and probes it for moves. /** Reads a Polyglot opening book (.bin file) and probes it for moves.
@@ -18,8 +18,6 @@ import scala.collection.mutable
*/ */
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)
@@ -95,7 +93,7 @@ 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 = rng.nextInt(totalWeight.max(1)) // NOSONAR val pick = ThreadLocalRandom.current().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 =