[SPARK-15364][ML][PYSPARK] Implement PySpark picklers for ml.Vector and ml.Matrix under spark.ml.python

## What changes were proposed in this pull request?

Now we have PySpark picklers for new and old vector/matrix, individually. However, they are all implemented under `PythonMLlibAPI`. To separate spark.mllib from spark.ml, we should implement the picklers of new vector/matrix under `spark.ml.python` instead.

## How was this patch tested?
Existing tests.

Author: Liang-Chi Hsieh <simonh@tw.ibm.com>

Closes #13219 from viirya/pyspark-pickler-ml.

1 files changed, 72 insertions, 0 deletions

diff --git a/mllib/src/test/scala/org/apache/spark/ml/python/MLSerDeSuite.scala b/mllib/src/test/scala/org/apache/spark/ml/python/MLSerDeSuite.scala
new file mode 100644
index 0000000000..5eaef9aabd
--- /dev/null
+++ b/mllib/src/test/scala/org/apache/spark/ml/python/MLSerDeSuite.scala
@@ -0,0 +1,72 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.ml.python
+
+import org.apache.spark.SparkFunSuite
+import org.apache.spark.ml.linalg.{DenseMatrix, Matrices, SparseMatrix, Vectors}
+
+class MLSerDeSuite extends SparkFunSuite {
+
+  MLSerDe.initialize()
+
+  test("pickle vector") {
+    val vectors = Seq(
+      Vectors.dense(Array.empty[Double]),
+      Vectors.dense(0.0),
+      Vectors.dense(0.0, -2.0),
+      Vectors.sparse(0, Array.empty[Int], Array.empty[Double]),
+      Vectors.sparse(1, Array.empty[Int], Array.empty[Double]),
+      Vectors.sparse(2, Array(1), Array(-2.0)))
+    vectors.foreach { v =>
+      val u = MLSerDe.loads(MLSerDe.dumps(v))
+      assert(u.getClass === v.getClass)
+      assert(u === v)
+    }
+  }
+
+  test("pickle double") {
+    for (x <- List(123.0, -10.0, 0.0, Double.MaxValue, Double.MinValue, Double.NaN)) {
+      val deser = MLSerDe.loads(MLSerDe.dumps(x.asInstanceOf[AnyRef])).asInstanceOf[Double]
+      // We use `equals` here for comparison because we cannot use `==` for NaN
+      assert(x.equals(deser))
+    }
+  }
+
+  test("pickle matrix") {
+    val values = Array[Double](0, 1.2, 3, 4.56, 7, 8)
+    val matrix = Matrices.dense(2, 3, values)
+    val nm = MLSerDe.loads(MLSerDe.dumps(matrix)).asInstanceOf[DenseMatrix]
+    assert(matrix === nm)
+
+    // Test conversion for empty matrix
+    val empty = Array[Double]()
+    val emptyMatrix = Matrices.dense(0, 0, empty)
+    val ne = MLSerDe.loads(MLSerDe.dumps(emptyMatrix)).asInstanceOf[DenseMatrix]
+    assert(emptyMatrix == ne)
+
+    val sm = new SparseMatrix(3, 2, Array(0, 1, 3), Array(1, 0, 2), Array(0.9, 1.2, 3.4))
+    val nsm = MLSerDe.loads(MLSerDe.dumps(sm)).asInstanceOf[SparseMatrix]
+    assert(sm.toArray === nsm.toArray)
+
+    val smt = new SparseMatrix(
+      3, 3, Array(0, 2, 3, 5), Array(0, 2, 1, 0, 2), Array(0.9, 1.2, 3.4, 5.7, 8.9),
+      isTransposed = true)
+    val nsmt = MLSerDe.loads(MLSerDe.dumps(smt)).asInstanceOf[SparseMatrix]
+    assert(smt.toArray === nsmt.toArray)
+  }
+}