[SPARK-9715] [ML] Store numFeatures in all ML PredictionModel types

All prediction models should store `numFeatures` indicating the number of features the model was trained on. Default value of -1 added for backwards compatibility.

Author: sethah <seth.hendrickson16@gmail.com>

Closes #8675 from sethah/SPARK-9715.

1 files changed, 8 insertions, 5 deletions

diff --git a/mllib/src/main/scala/org/apache/spark/ml/classification/DecisionTreeClassifier.scala b/mllib/src/main/scala/org/apache/spark/ml/classification/DecisionTreeClassifier.scala
index b8eb49f9bd..a6f6d463bf 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/classification/DecisionTreeClassifier.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/classification/DecisionTreeClassifier.scala
@@ -107,6 +107,7 @@ object DecisionTreeClassifier {
 final class DecisionTreeClassificationModel private[ml] (
     override val uid: String,
     override val rootNode: Node,
+    override val numFeatures: Int,
     override val numClasses: Int)
   extends ProbabilisticClassificationModel[Vector, DecisionTreeClassificationModel]
   with DecisionTreeModel with Serializable {
@@ -118,8 +119,8 @@ final class DecisionTreeClassificationModel private[ml] (
    * Construct a decision tree classification model.
    * @param rootNode  Root node of tree, with other nodes attached.
    */
-  private[ml] def this(rootNode: Node, numClasses: Int) =
-    this(Identifiable.randomUID("dtc"), rootNode, numClasses)
+  private[ml] def this(rootNode: Node, numFeatures: Int, numClasses: Int) =
+    this(Identifiable.randomUID("dtc"), rootNode, numFeatures, numClasses)
 
   override protected def predict(features: Vector): Double = {
     rootNode.predictImpl(features).prediction
@@ -141,7 +142,7 @@ final class DecisionTreeClassificationModel private[ml] (
   }
 
   override def copy(extra: ParamMap): DecisionTreeClassificationModel = {
-    copyValues(new DecisionTreeClassificationModel(uid, rootNode, numClasses), extra)
+    copyValues(new DecisionTreeClassificationModel(uid, rootNode, numFeatures, numClasses), extra)
       .setParent(parent)
   }
 
@@ -161,12 +162,14 @@ private[ml] object DecisionTreeClassificationModel {
   def fromOld(
       oldModel: OldDecisionTreeModel,
       parent: DecisionTreeClassifier,
-      categoricalFeatures: Map[Int, Int]): DecisionTreeClassificationModel = {
+      categoricalFeatures: Map[Int, Int],
+      numFeatures: Int = -1): DecisionTreeClassificationModel = {
     require(oldModel.algo == OldAlgo.Classification,
       s"Cannot convert non-classification DecisionTreeModel (old API) to" +
         s" DecisionTreeClassificationModel (new API).  Algo is: ${oldModel.algo}")
     val rootNode = Node.fromOld(oldModel.topNode, categoricalFeatures)
     val uid = if (parent != null) parent.uid else Identifiable.randomUID("dtc")
-    new DecisionTreeClassificationModel(uid, rootNode, -1)
+    // Can't infer number of features from old model, so default to -1
+    new DecisionTreeClassificationModel(uid, rootNode, numFeatures, -1)
   }
 }