Merge pull request #807 from rpiotrow/bugfix/806-ThreadLocalRandomGen…

…erator-not-serializable

Make thread local field transient in `ThreadLocalRandomGenerator`

math/src/main/scala/breeze/stats/distributions/ThreadLocalRandomGenerator.scala

@@ -9,7 +9,7 @@ import org.apache.commons.math3.random.RandomGenerator
  **/
 @SerialVersionUID(1L)
 class ThreadLocalRandomGenerator(genThunk: => RandomGenerator) extends RandomGenerator with Serializable {
-  private val genTL = new ThreadLocal[RandomGenerator] {
+  @transient private lazy val genTL = new ThreadLocal[RandomGenerator] {
     override def initialValue(): RandomGenerator = genThunk
   }
   def nextBytes(bytes: Array[Byte]) = genTL.get().nextBytes(bytes)

math/src/test/scala/breeze/stats/distributions/ThreadLocalRandomGeneratorTest.scala

@@ -0,0 +1,53 @@
+package breeze.stats.distributions
+
+import org.apache.commons.math3.random.MersenneTwister
+import org.scalatest.{FunSuite, Matchers}
+
+import java.io._
+
+class ThreadLocalRandomGeneratorTest extends FunSuite with Matchers {
+  test("ThreadLocalRandomGeneratorTest should be serializable") {
+    val generator = new ThreadLocalRandomGenerator(new MersenneTwister())
+    serialize(generator)
+  }
+
+  test("ThreadLocalRandomGeneratorTest should be serializable after usage") {
+    val generator = new ThreadLocalRandomGenerator(new MersenneTwister())
+    generator.nextInt()
+    serialize(generator)
+  }
+
+  test("ThreadLocalRandomGeneratorTest should be deserializable") {
+    val generator = new ThreadLocalRandomGenerator(new MersenneTwister())
+    val i1 = generator.nextInt()
+    val bytes = serialize(generator)
+    val deserialized = deserialize(bytes)
+    val i2 = deserialized.nextInt()
+
+    i1 should not be i2
+  }
+
+  private def serialize(generator: ThreadLocalRandomGenerator): Array[Byte] = {
+    val outputStream = new ByteArrayOutputStream(512)
+    val out = new ObjectOutputStream(outputStream)
+    try {
+      out.writeObject(generator)
+      outputStream.toByteArray
+    } catch {
+      case _: IOException => fail("cannot serialize")
+    } finally {
+      if (out != null) out.close()
+    }
+  }
+
+  private def deserialize(bytes: Array[Byte]): ThreadLocalRandomGenerator = {
+    val in = new ObjectInputStream(new ByteArrayInputStream(bytes))
+    try {
+      in.readObject().asInstanceOf[ThreadLocalRandomGenerator]
+    } catch {
+      case _: IOException => fail("cannot deserialize")
+    } finally {
+      if (in != null) in.close()
+    }
+  }
+}