Merge pull request #53 from isaacl/fixThreadLocalRandom

Fix ThreadLocalRandom
lichess-org · Sep 13, 2024 · aa2235c · aa2235c
2 parents a104e9b + b95b9eb
commit aa2235c
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diff --git a/lila/src/main/scala/Random.scala b/lila/src/main/scala/Random.scala
@@ -2,7 +2,10 @@ package scalalib
 
 import scala.collection.mutable.StringBuilder
 
-val ThreadLocalRandom = RandomApi(java.util.concurrent.ThreadLocalRandom.current)
+private final val store =
+  java.lang.ThreadLocal.withInitial(() => RandomApi(java.util.concurrent.ThreadLocalRandom.current))
+
+def ThreadLocalRandom = store.get
 
 val SecureRandom = RandomApi(java.security.SecureRandom())
 

diff --git a/lila/src/test/scala/RandomTest.scala b/lila/src/test/scala/RandomTest.scala
@@ -0,0 +1,12 @@
+package scalalib
+
+class RandomTest extends munit.FunSuite:
+
+  test("different threads get different randoms"):
+    val r1 = ThreadLocalRandom
+
+    @volatile var r2: RandomApi = null
+    val thread2                 = new Thread(() => r2 = ThreadLocalRandom)
+    thread2.start()
+    thread2.join()
+    assertNotEquals(r1, r2)