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From jkbradley <...@git.apache.org>
Subject [GitHub] spark pull request: [SPARK-3530][MLLIB] pipeline and parameters wi...
Date Mon, 10 Nov 2014 20:43:15 GMT
Github user jkbradley commented on a diff in the pull request:

    https://github.com/apache/spark/pull/3099#discussion_r20111093
  
    --- Diff: mllib/src/main/scala/org/apache/spark/ml/Pipeline.scala ---
    @@ -0,0 +1,136 @@
    +/*
    + * 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.collection.mutable.ListBuffer
    +
    +import org.apache.spark.Logging
    +import org.apache.spark.ml.param.{Param, ParamMap}
    +import org.apache.spark.sql.{SchemaRDD, StructType}
    +
    +/**
    + * A stage in a pipeline, either an Estimator or an Transformer.
    + */
    +abstract class PipelineStage extends Serializable with Logging {
    +
    +  /**
    +   * Derives the output schema from the input schema and parameters.
    +   */
    +  def transform(schema: StructType, paramMap: ParamMap): StructType
    +
    +  /**
    +   * Drives the output schema from the input schema and parameters, optionally with logging.
    +   */
    +  protected def transform(schema: StructType, paramMap: ParamMap, logging: Boolean):
StructType = {
    +    if (logging) {
    +      logDebug(s"Input schema: ${schema.json}")
    +    }
    +    val outputSchema = transform(schema, paramMap)
    +    if (logging) {
    +      logDebug(s"Expected output schema: ${outputSchema.json}")
    +    }
    +    outputSchema
    +  }
    +}
    +
    +/**
    + * A simple pipeline, which acts as an estimator.
    + */
    +class Pipeline extends Estimator[PipelineModel] {
    +
    +  val stages: Param[Array[PipelineStage]] = new Param(this, "stages", "stages of the
pipeline")
    +  def setStages(value: Array[PipelineStage]): this.type = { set(stages, value); this
}
    +  def getStages: Array[PipelineStage] = get(stages)
    +
    +  override def fit(dataset: SchemaRDD, paramMap: ParamMap): PipelineModel = {
    +    transform(dataset.schema, paramMap, logging = true)
    +    val map = this.paramMap ++ paramMap
    +    val theStages = map(stages)
    +    // Search for the last estimator.
    +    var lastIndexOfEstimator = -1
    +    theStages.view.zipWithIndex.foreach { case (stage, index) =>
    +      stage match {
    +        case _: Estimator[_] =>
    +          lastIndexOfEstimator = index
    +        case _ =>
    +      }
    +    }
    +    var curDataset = dataset
    +    val transformers = ListBuffer.empty[Transformer]
    +    theStages.view.zipWithIndex.foreach { case (stage, index) =>
    +      stage match {
    +        case estimator: Estimator[_] =>
    +          val transformer = estimator.fit(curDataset, paramMap)
    +          if (index < lastIndexOfEstimator) {
    +            curDataset = transformer.transform(curDataset, paramMap)
    +          }
    +          transformers += transformer
    +        case transformer: Transformer =>
    +          if (index < lastIndexOfEstimator) {
    +            curDataset = transformer.transform(curDataset, paramMap)
    +          }
    +          transformers += transformer
    +        case _ =>
    +          throw new IllegalArgumentException
    +      }
    +    }
    +
    +    new PipelineModel(this, map, transformers.toArray)
    +  }
    +
    +  override def transform(schema: StructType, paramMap: ParamMap): StructType = {
    --- End diff --
    
    Should this be a required method in all Estimators and Transformers since Pipeline seems
to expect it?
    
    Also, doc needed.
    
    Also, maybe rename to checkTransform?


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