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/*
 * 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.feature

import org.apache.spark.SparkFunSuite
import org.apache.spark.ml.util.DefaultReadWriteTest
import org.apache.spark.mllib.util.MLlibTestSparkContext
import org.apache.spark.sql.SparkSession
import org.apache.spark.sql.functions.udf

class QuantileDiscretizerSuite
  extends SparkFunSuite with MLlibTestSparkContext with DefaultReadWriteTest {

  test("Test observed number of buckets and their sizes match expected values") {
    val spark = this.spark
    import spark.implicits._

    val datasetSize = 100000
    val numBuckets = 5
    val df = sc.parallelize(1.0 to datasetSize by 1.0).map(Tuple1.apply).toDF("input")
    val discretizer = new QuantileDiscretizer()
      .setInputCol("input")
      .setOutputCol("result")
      .setNumBuckets(numBuckets)
    val result = discretizer.fit(df).transform(df)

    val observedNumBuckets = result.select("result").distinct.count
    assert(observedNumBuckets === numBuckets,
      "Observed number of buckets does not equal expected number of buckets.")

    val relativeError = discretizer.getRelativeError
    val isGoodBucket = udf {
      (size: Int) => math.abs( size - (datasetSize / numBuckets)) <= (relativeError * datasetSize)
    }
    val numGoodBuckets = result.groupBy("result").count.filter(isGoodBucket($"count")).count
    assert(numGoodBuckets === numBuckets,
      "Bucket sizes are not within expected relative error tolerance.")
  }

  test("Test Bucketizer on duplicated splits") {
    val spark = this.spark
    import spark.implicits._

    val datasetSize = 12
    val numBuckets = 5
    val df = sc.parallelize(Array(1.0, 3.0, 2.0, 1.0, 1.0, 2.0, 3.0, 2.0, 2.0, 2.0, 1.0, 3.0))
      .map(Tuple1.apply).toDF("input")
    val discretizer = new QuantileDiscretizer()
      .setInputCol("input")
      .setOutputCol("result")
      .setNumBuckets(numBuckets)
    val result = discretizer.fit(df).transform(df)

    val observedNumBuckets = result.select("result").distinct.count
    assert(2 <= observedNumBuckets && observedNumBuckets <= numBuckets,
      "Observed number of buckets are not within expected range.")
  }

  test("Test transform method on unseen data") {
    val spark = this.spark
    import spark.implicits._

    val trainDF = sc.parallelize(1.0 to 100.0 by 1.0).map(Tuple1.apply).toDF("input")
    val testDF = sc.parallelize(-10.0 to 110.0 by 1.0).map(Tuple1.apply).toDF("input")
    val discretizer = new QuantileDiscretizer()
      .setInputCol("input")
      .setOutputCol("result")
      .setNumBuckets(5)

    val result = discretizer.fit(trainDF).transform(testDF)
    val firstBucketSize = result.filter(result("result") === 0.0).count
    val lastBucketSize = result.filter(result("result") === 4.0).count

    assert(firstBucketSize === 30L,
      s"Size of first bucket ${firstBucketSize} did not equal expected value of 30.")
    assert(lastBucketSize === 31L,
      s"Size of last bucket ${lastBucketSize} did not equal expected value of 31.")
  }

  test("read/write") {
    val t = new QuantileDiscretizer()
      .setInputCol("myInputCol")
      .setOutputCol("myOutputCol")
      .setNumBuckets(6)
    testDefaultReadWrite(t)
  }

  test("Verify resulting model has parent") {
    val spark = this.spark
    import spark.implicits._

    val df = sc.parallelize(1 to 100).map(Tuple1.apply).toDF("input")
    val discretizer = new QuantileDiscretizer()
      .setInputCol("input")
      .setOutputCol("result")
      .setNumBuckets(5)
    val model = discretizer.fit(df)
    assert(model.hasParent)
  }
}