Github user mengxr commented on a diff in the pull request:
https://github.com/apache/spark/pull/2435#discussion_r17943442
--- Diff:
mllib/src/main/scala/org/apache/spark/mllib/tree/impl/BaggedPoint.scala ---
@@ -0,0 +1,80 @@
+/*
+ * 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.mllib.tree.impl
+
+import cern.jet.random.Poisson
+import cern.jet.random.engine.DRand
+import org.apache.spark.rdd.RDD
+import org.apache.spark.util.Utils
+
+/**
+ * Internal representation of a datapoint which belongs to several
subsamples of the same dataset,
+ * particularly for bagging (e.g., for random forests).
+ *
+ * This holds one instance, as well as an array of weights which represent
the (weighted)
+ * number of times which this instance appears in each subsample.
+ * E.g., (datum, [1, 0, 4]) indicates that there are 3 subsamples of the
dataset and that
+ * this datum has 1 copy, 0 copies, and 4 copies in the 3 subsamples,
respectively.
+ *
+ * @param datum Data instance
+ * @param subsampleWeights Weight of this instance in each subsampled
dataset.
+ *
+ * TODO: This does not currently support (Double) weighted instances.
Once MLlib has weighted
+ * dataset support, update. (We store subsampleWeights as Double
for this future extension.)
+ */
+private[tree] class BaggedPoint[Datum](val datum: Datum, val
subsampleWeights: Array[Double])
+ extends Serializable {
+}
+
+private[tree] object BaggedPoint {
+
+ /**
+ * Convert an input dataset into its BaggedPoint representation,
+ * choosing subsample counts for each instance.
+ * Each subsample has the same number of instances as the original
dataset,
+ * and is created by subsampling with replacement.
+ * @param input Input dataset.
+ * @param numSubsamples Number of subsamples of this RDD to take.
+ * @param seed Random seed.
+ * @return BaggedPoint dataset representation
+ */
+ def convertToBaggedRDD[Datum](
+ input: RDD[Datum],
+ numSubsamples: Int,
+ seed: Int = Utils.random.nextInt()): RDD[BaggedPoint[Datum]] = {
--- End diff --
use `Long` for random seed
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