Github user tillrohrmann commented on a diff in the pull request:
https://github.com/apache/flink/pull/1220#discussion_r63698942
--- Diff:
flink-libraries/flink-ml/src/main/scala/org/apache/flink/ml/nn/KNN.scala ---
@@ -0,0 +1,354 @@
+/*
+ * 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.flink.ml.nn
+
+import org.apache.flink.api.common.operators.Order
+import org.apache.flink.api.common.typeinfo.TypeInformation
+import org.apache.flink.api.scala.utils._
+import org.apache.flink.api.scala._
+import org.apache.flink.ml.common._
+import org.apache.flink.ml.math.{Vector => FlinkVector, DenseVector}
+import
org.apache.flink.ml.metrics.distances.{SquaredEuclideanDistanceMetric,
DistanceMetric,
+EuclideanDistanceMetric}
+import org.apache.flink.ml.pipeline.{FitOperation,
PredictDataSetOperation, Predictor}
+import org.apache.flink.util.Collector
+import
org.apache.flink.api.common.operators.base.CrossOperatorBase.CrossHint
+
+import scala.collection.immutable.Vector
+import scala.collection.mutable
+import scala.collection.mutable.ArrayBuffer
+import scala.reflect.ClassTag
+
+/** Implements a k-nearest neighbor join.
+ *
+ * Calculates the `k`-nearest neighbor points in the training set for
each point in the test set.
+ *
+ * @example
+ * {{{
+ * val trainingDS: DataSet[Vector] = ...
+ * val testingDS: DataSet[Vector] = ...
+ *
+ * val knn = KNN()
+ * .setK(10)
+ * .setBlocks(5)
+ * .setDistanceMetric(EuclideanDistanceMetric())
+ *
+ * knn.fit(trainingDS)
+ *
+ * val predictionDS: DataSet[(Vector, Array[Vector])] =
knn.predict(testingDS)
+ * }}}
+ *
+ * =Parameters=
+ *
+ * - [[org.apache.flink.ml.nn.KNN.K]]
+ * Sets the K which is the number of selected points as neighbors.
(Default value: '''5''')
+ *
+ * - [[org.apache.flink.ml.nn.KNN.DistanceMetric]]
+ * Sets the distance metric we use to calculate the distance between two
points. If no metric is
+ * specified, then
[[org.apache.flink.ml.metrics.distances.EuclideanDistanceMetric]] is used.
+ * (Default value: '''EuclideanDistanceMetric()''')
+ *
+ * - [[org.apache.flink.ml.nn.KNN.Blocks]]
+ * Sets the number of blocks into which the input data will be split.
This number should be set
+ * at least to the degree of parallelism. If no value is specified, then
the parallelism of the
+ * input [[DataSet]] is used as the number of blocks. (Default value:
'''None''')
+ *
+ * - [[org.apache.flink.ml.nn.KNN.UseQuadTreeParam]]
+ * A boolean variable that whether or not to use a Quadtree to partition
the training set
+ * to potentially simplify the KNN search. If no value is specified, the
code will
+ * automatically decide whether or not to use a Quadtree. Use of a
Quadtree scales well
+ * with the number of training and testing points, though poorly with the
dimension.
+ * (Default value: ```None```)
+ *
+ * - [[org.apache.flink.ml.nn.KNN.SizeHint]]
+ * Specifies whether the training set or test set is small to optimize
the cross
+ * product operation needed for the KNN search. If the training set is
small
+ * this should be `CrossHint.FIRST_IS_SMALL` and set to
`CrossHint.SECOND_IS_SMALL`
+ * if the test set is small.
+ * (Default value: ```None```)
+ *
+ */
+
+class KNN extends Predictor[KNN] {
+
+ import KNN._
+
+ var trainingSet: Option[DataSet[Block[FlinkVector]]] = None
+
+ /** Sets K
+ * @param k the number of selected points as neighbors
+ */
+ def setK(k: Int): KNN = {
+ require(k > 0, "K must be positive.")
+ parameters.add(K, k)
+ this
+ }
+
+ /** Sets the distance metric
+ * @param metric the distance metric to calculate distance between two
points
+ */
+ def setDistanceMetric(metric: DistanceMetric): KNN = {
+ parameters.add(DistanceMetric, metric)
+ this
+ }
+
+ /** Sets the number of data blocks/partitions
+ * @param n the number of data blocks
+ */
+ def setBlocks(n: Int): KNN = {
+ require(n > 0, "Number of blocks must be positive.")
+ parameters.add(Blocks, n)
+ this
+ }
+
+ /**
+ * Sets the Boolean variable that decides whether to use the QuadTree or
not
+ */
+ def setUseQuadTree(useQuadTree: Boolean): KNN = {
+ if (useQuadTree){
+
require(parameters(DistanceMetric).isInstanceOf[SquaredEuclideanDistanceMetric]
||
+ parameters(DistanceMetric).isInstanceOf[EuclideanDistanceMetric])
--- End diff --
What happens if we change the distance metric after we've activated the
quad tree usage? Is this condition checked later on again?
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