Github user jkbradley commented on a diff in the pull request:
https://github.com/apache/spark/pull/3637#discussion_r21497595
--- Diff: mllib/src/main/scala/org/apache/spark/ml/LabeledPoint.scala ---
@@ -0,0 +1,52 @@
+/*
+ * 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
+
+import scala.beans.BeanInfo
+
+import org.apache.spark.annotation.AlphaComponent
+import org.apache.spark.mllib.linalg.Vector
+
+/**
+ * :: AlphaComponent ::
+ * Class that represents an instance (data point) for prediction tasks.
+ *
+ * @param label Label to predict
+ * @param features List of features describing this instance
+ * @param weight Instance weight
+ */
+@AlphaComponent
+@BeanInfo
+case class LabeledPoint(label: Double, features: Vector, weight: Double) {
--- End diff --
I agree with you about strong types being nice. I think optimizations with
using fewer bits should remain internal. For the user-facing API, it's really
a question about whether we want to incur some extra overhead with strong types:
* Users & developers have to write LabeledPoint[Double, Vector] or
LabeledPoint[Int, Vector] instead of LabeledPoint.
* As far as I know, we can't have default type parameters, so users could
never write LabeledPoint. (a rare time I miss C++)
* Algorithm APIs get messier to look at (passing about LabelType and
FeaturesType). This is especially annoying with meta-algorithms (boosting &
bagging).
Personally, I'd be OK with heavy typing (coming from C++ land), but it
might offend some Scala users.
CC: @mengxr since I know you have opinions about this
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