From b8a422f6cef0e15026745b44a0906e586aaa11b6 Mon Sep 17 00:00:00 2001
From: Rafal Piotrowski <rpiotrowski@citrine.io>
Date: Mon, 19 Apr 2021 16:33:32 +0200
Subject: [PATCH 1/2] Make thread local field transient in
 `ThreadLocalRandomGenerator`

Make it also lazy to not create ThreadLocal until it is used.

Fixes #806
---
 .../ThreadLocalRandomGenerator.scala          |  2 +-
 .../ThreadLocalRandomGeneratorTest.scala      | 54 +++++++++++++++++++
 2 files changed, 55 insertions(+), 1 deletion(-)
 create mode 100644 math/src/test/scala/breeze/stats/distributions/ThreadLocalRandomGeneratorTest.scala

diff --git a/math/src/main/scala/breeze/stats/distributions/ThreadLocalRandomGenerator.scala b/math/src/main/scala/breeze/stats/distributions/ThreadLocalRandomGenerator.scala
index bc76fa344..fc293e7c7 100644
--- a/math/src/main/scala/breeze/stats/distributions/ThreadLocalRandomGenerator.scala
+++ b/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)
diff --git a/math/src/test/scala/breeze/stats/distributions/ThreadLocalRandomGeneratorTest.scala b/math/src/test/scala/breeze/stats/distributions/ThreadLocalRandomGeneratorTest.scala
new file mode 100644
index 000000000..0a18623e2
--- /dev/null
+++ b/math/src/test/scala/breeze/stats/distributions/ThreadLocalRandomGeneratorTest.scala
@@ -0,0 +1,54 @@
+package breeze.stats.distributions
+
+import com.sun.xml.internal.ws.encoding.soap.SerializationException
+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 ex: IOException => throw new SerializationException(ex)
+    } 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 ex: IOException => throw new SerializationException(ex)
+    } finally {
+      if (in != null) in.close()
+    }
+  }
+}

From bf0ef50ab9566817b539c32ee2b03e65ccbebdd9 Mon Sep 17 00:00:00 2001
From: Rafal Piotrowski <rpiotrowski@iteratorshq.com>
Date: Mon, 19 Apr 2021 21:05:33 +0200
Subject: [PATCH 2/2] Fix imports

---
 .../stats/distributions/ThreadLocalRandomGeneratorTest.scala | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/math/src/test/scala/breeze/stats/distributions/ThreadLocalRandomGeneratorTest.scala b/math/src/test/scala/breeze/stats/distributions/ThreadLocalRandomGeneratorTest.scala
index 0a18623e2..f8595e4c3 100644
--- a/math/src/test/scala/breeze/stats/distributions/ThreadLocalRandomGeneratorTest.scala
+++ b/math/src/test/scala/breeze/stats/distributions/ThreadLocalRandomGeneratorTest.scala
@@ -1,6 +1,5 @@
 package breeze.stats.distributions
 
-import com.sun.xml.internal.ws.encoding.soap.SerializationException
 import org.apache.commons.math3.random.MersenneTwister
 import org.scalatest.{FunSuite, Matchers}
 
@@ -35,7 +34,7 @@ class ThreadLocalRandomGeneratorTest extends FunSuite with Matchers {
       out.writeObject(generator)
       outputStream.toByteArray
     } catch {
-      case ex: IOException => throw new SerializationException(ex)
+      case _: IOException => fail("cannot serialize")
     } finally {
       if (out != null) out.close()
     }
@@ -46,7 +45,7 @@ class ThreadLocalRandomGeneratorTest extends FunSuite with Matchers {
     try {
       in.readObject().asInstanceOf[ThreadLocalRandomGenerator]
     } catch {
-      case ex: IOException => throw new SerializationException(ex)
+      case _: IOException => fail("cannot deserialize")
     } finally {
       if (in != null) in.close()
     }