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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
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 #
 import itertools
 import sys
 from multiprocessing.pool import ThreadPool
 
 import numpy as np
 
 from pyspark import since, keyword_only
 from pyspark.ml import Estimator, Model
 from pyspark.ml.common import _py2java, _java2py
 from pyspark.ml.param import Params, Param, TypeConverters
 from pyspark.ml.param.shared import HasCollectSubModels, HasParallelism, HasSeed
 from pyspark.ml.util import *
 from pyspark.ml.wrapper import JavaParams
 from pyspark.sql.functions import rand
 
 __all__ = ['ParamGridBuilder', 'CrossValidator', 'CrossValidatorModel', 'TrainValidationSplit',
            'TrainValidationSplitModel']
 
 
 def _parallelFitTasks(est, train, eva, validation, epm, collectSubModel):
     """
     Creates a list of callables which can be called from different threads to fit and evaluate
     an estimator in parallel. Each callable returns an `(index, metric)` pair.
 
     :param est: Estimator, the estimator to be fit.
     :param train: DataFrame, training data set, used for fitting.
     :param eva: Evaluator, used to compute `metric`
     :param validation: DataFrame, validation data set, used for evaluation.
     :param epm: Sequence of ParamMap, params maps to be used during fitting & evaluation.
     :param collectSubModel: Whether to collect sub model.
     :return: (int, float, subModel), an index into `epm` and the associated metric value.
     """
     modelIter = est.fitMultiple(train, epm)
 
     def singleTask():
         index, model = next(modelIter)
         metric = eva.evaluate(model.transform(validation, epm[index]))
         return index, metric, model if collectSubModel else None
 
     return [singleTask] * len(epm)
 
 
 class ParamGridBuilder(object):
     r"""
     Builder for a param grid used in grid search-based model selection.
 
     >>> from pyspark.ml.classification import LogisticRegression
     >>> lr = LogisticRegression()
     >>> output = ParamGridBuilder() \
     ...     .baseOn({lr.labelCol: 'l'}) \
     ...     .baseOn([lr.predictionCol, 'p']) \
     ...     .addGrid(lr.regParam, [1.0, 2.0]) \
     ...     .addGrid(lr.maxIter, [1, 5]) \
     ...     .build()
     >>> expected = [
     ...     {lr.regParam: 1.0, lr.maxIter: 1, lr.labelCol: 'l', lr.predictionCol: 'p'},
     ...     {lr.regParam: 2.0, lr.maxIter: 1, lr.labelCol: 'l', lr.predictionCol: 'p'},
     ...     {lr.regParam: 1.0, lr.maxIter: 5, lr.labelCol: 'l', lr.predictionCol: 'p'},
     ...     {lr.regParam: 2.0, lr.maxIter: 5, lr.labelCol: 'l', lr.predictionCol: 'p'}]
     >>> len(output) == len(expected)
     True
     >>> all([m in expected for m in output])
     True
 
     .. versionadded:: 1.4.0
     """
 
     def __init__(self):
         self._param_grid = {}
 
     @since("1.4.0")
     def addGrid(self, param, values):
         """
         Sets the given parameters in this grid to fixed values.
 
         param must be an instance of Param associated with an instance of Params
         (such as Estimator or Transformer).
         """
         if isinstance(param, Param):
             self._param_grid[param] = values
         else:
             raise TypeError("param must be an instance of Param")
 
         return self
 
     @since("1.4.0")
     def baseOn(self, *args):
         """
         Sets the given parameters in this grid to fixed values.
         Accepts either a parameter dictionary or a list of (parameter, value) pairs.
         """
         if isinstance(args[0], dict):
             self.baseOn(*args[0].items())
         else:
             for (param, value) in args:
                 self.addGrid(param, [value])
 
         return self
 
     @since("1.4.0")
     def build(self):
         """
         Builds and returns all combinations of parameters specified
         by the param grid.
         """
         keys = self._param_grid.keys()
         grid_values = self._param_grid.values()
 
         def to_key_value_pairs(keys, values):
             return [(key, key.typeConverter(value)) for key, value in zip(keys, values)]
 
         return [dict(to_key_value_pairs(keys, prod)) for prod in itertools.product(*grid_values)]
 
 
 class _ValidatorParams(HasSeed):
     """
     Common params for TrainValidationSplit and CrossValidator.
     """
 
     estimator = Param(Params._dummy(), "estimator", "estimator to be cross-validated")
     estimatorParamMaps = Param(Params._dummy(), "estimatorParamMaps", "estimator param maps")
     evaluator = Param(
         Params._dummy(), "evaluator",
         "evaluator used to select hyper-parameters that maximize the validator metric")
 
     @since("2.0.0")
     def getEstimator(self):
         """
         Gets the value of estimator or its default value.
         """
         return self.getOrDefault(self.estimator)
 
     @since("2.0.0")
     def getEstimatorParamMaps(self):
         """
         Gets the value of estimatorParamMaps or its default value.
         """
         return self.getOrDefault(self.estimatorParamMaps)
 
     @since("2.0.0")
     def getEvaluator(self):
         """
         Gets the value of evaluator or its default value.
         """
         return self.getOrDefault(self.evaluator)
 
     @classmethod
     def _from_java_impl(cls, java_stage):
         """
         Return Python estimator, estimatorParamMaps, and evaluator from a Java ValidatorParams.
         """
 
         # Load information from java_stage to the instance.
         estimator = JavaParams._from_java(java_stage.getEstimator())
         evaluator = JavaParams._from_java(java_stage.getEvaluator())
         epms = [estimator._transfer_param_map_from_java(epm)
                 for epm in java_stage.getEstimatorParamMaps()]
         return estimator, epms, evaluator
 
     def _to_java_impl(self):
         """
         Return Java estimator, estimatorParamMaps, and evaluator from this Python instance.
         """
 
         gateway = SparkContext._gateway
         cls = SparkContext._jvm.org.apache.spark.ml.param.ParamMap
 
         java_epms = gateway.new_array(cls, len(self.getEstimatorParamMaps()))
         for idx, epm in enumerate(self.getEstimatorParamMaps()):
             java_epms[idx] = self.getEstimator()._transfer_param_map_to_java(epm)
 
         java_estimator = self.getEstimator()._to_java()
         java_evaluator = self.getEvaluator()._to_java()
         return java_estimator, java_epms, java_evaluator
 
 
 class _CrossValidatorParams(_ValidatorParams):
     """
     Params for :py:class:`CrossValidator` and :py:class:`CrossValidatorModel`.
 
     .. versionadded:: 3.0.0
     """
 
     numFolds = Param(Params._dummy(), "numFolds", "number of folds for cross validation",
                      typeConverter=TypeConverters.toInt)
 
     @since("1.4.0")
     def getNumFolds(self):
         """
         Gets the value of numFolds or its default value.
         """
         return self.getOrDefault(self.numFolds)
 
 
 class CrossValidator(Estimator, _CrossValidatorParams, HasParallelism, HasCollectSubModels,
                      MLReadable, MLWritable):
     """
 
     K-fold cross validation performs model selection by splitting the dataset into a set of
     non-overlapping randomly partitioned folds which are used as separate training and test datasets
     e.g., with k=3 folds, K-fold cross validation will generate 3 (training, test) dataset pairs,
     each of which uses 2/3 of the data for training and 1/3 for testing. Each fold is used as the
     test set exactly once.
 
 
     >>> from pyspark.ml.classification import LogisticRegression
     >>> from pyspark.ml.evaluation import BinaryClassificationEvaluator
     >>> from pyspark.ml.linalg import Vectors
     >>> from pyspark.ml.tuning import CrossValidatorModel
     >>> import tempfile
     >>> dataset = spark.createDataFrame(
     ...     [(Vectors.dense([0.0]), 0.0),
     ...      (Vectors.dense([0.4]), 1.0),
     ...      (Vectors.dense([0.5]), 0.0),
     ...      (Vectors.dense([0.6]), 1.0),
     ...      (Vectors.dense([1.0]), 1.0)] * 10,
     ...     ["features", "label"])
     >>> lr = LogisticRegression()
     >>> grid = ParamGridBuilder().addGrid(lr.maxIter, [0, 1]).build()
     >>> evaluator = BinaryClassificationEvaluator()
     >>> cv = CrossValidator(estimator=lr, estimatorParamMaps=grid, evaluator=evaluator,
     ...     parallelism=2)
     >>> cvModel = cv.fit(dataset)
     >>> cvModel.getNumFolds()
     3
     >>> cvModel.avgMetrics[0]
     0.5
     >>> path = tempfile.mkdtemp()
     >>> model_path = path + "/model"
     >>> cvModel.write().save(model_path)
     >>> cvModelRead = CrossValidatorModel.read().load(model_path)
     >>> cvModelRead.avgMetrics
     [0.5, ...
     >>> evaluator.evaluate(cvModel.transform(dataset))
     0.8333...
 
     .. versionadded:: 1.4.0
     """
 
     @keyword_only
     def __init__(self, estimator=None, estimatorParamMaps=None, evaluator=None, numFolds=3,
                  seed=None, parallelism=1, collectSubModels=False):
         """
         __init__(self, estimator=None, estimatorParamMaps=None, evaluator=None, numFolds=3,\
                  seed=None, parallelism=1, collectSubModels=False)
         """
         super(CrossValidator, self).__init__()
         self._setDefault(numFolds=3, parallelism=1)
         kwargs = self._input_kwargs
         self._set(**kwargs)
 
     @keyword_only
     @since("1.4.0")
     def setParams(self, estimator=None, estimatorParamMaps=None, evaluator=None, numFolds=3,
                   seed=None, parallelism=1, collectSubModels=False):
         """
         setParams(self, estimator=None, estimatorParamMaps=None, evaluator=None, numFolds=3,\
                   seed=None, parallelism=1, collectSubModels=False):
         Sets params for cross validator.
         """
         kwargs = self._input_kwargs
         return self._set(**kwargs)
 
     @since("2.0.0")
     def setEstimator(self, value):
         """
         Sets the value of :py:attr:`estimator`.
         """
         return self._set(estimator=value)
 
     @since("2.0.0")
     def setEstimatorParamMaps(self, value):
         """
         Sets the value of :py:attr:`estimatorParamMaps`.
         """
         return self._set(estimatorParamMaps=value)
 
     @since("2.0.0")
     def setEvaluator(self, value):
         """
         Sets the value of :py:attr:`evaluator`.
         """
         return self._set(evaluator=value)
 
     @since("1.4.0")
     def setNumFolds(self, value):
         """
         Sets the value of :py:attr:`numFolds`.
         """
         return self._set(numFolds=value)
 
     def setSeed(self, value):
         """
         Sets the value of :py:attr:`seed`.
         """
         return self._set(seed=value)
 
     def setParallelism(self, value):
         """
         Sets the value of :py:attr:`parallelism`.
         """
         return self._set(parallelism=value)
 
     def setCollectSubModels(self, value):
         """
         Sets the value of :py:attr:`collectSubModels`.
         """
         return self._set(collectSubModels=value)
 
     def _fit(self, dataset):
         est = self.getOrDefault(self.estimator)
         epm = self.getOrDefault(self.estimatorParamMaps)
         numModels = len(epm)
         eva = self.getOrDefault(self.evaluator)
         nFolds = self.getOrDefault(self.numFolds)
         seed = self.getOrDefault(self.seed)
         h = 1.0 / nFolds
         randCol = self.uid + "_rand"
         df = dataset.select("*", rand(seed).alias(randCol))
         metrics = [0.0] * numModels
 
         pool = ThreadPool(processes=min(self.getParallelism(), numModels))
         subModels = None
         collectSubModelsParam = self.getCollectSubModels()
         if collectSubModelsParam:
             subModels = [[None for j in range(numModels)] for i in range(nFolds)]
 
         for i in range(nFolds):
             validateLB = i * h
             validateUB = (i + 1) * h
             condition = (df[randCol] >= validateLB) & (df[randCol] < validateUB)
             validation = df.filter(condition).cache()
             train = df.filter(~condition).cache()
 
             tasks = _parallelFitTasks(est, train, eva, validation, epm, collectSubModelsParam)
             for j, metric, subModel in pool.imap_unordered(lambda f: f(), tasks):
                 metrics[j] += (metric / nFolds)
                 if collectSubModelsParam:
                     subModels[i][j] = subModel
 
             validation.unpersist()
             train.unpersist()
 
         if eva.isLargerBetter():
             bestIndex = np.argmax(metrics)
         else:
             bestIndex = np.argmin(metrics)
         bestModel = est.fit(dataset, epm[bestIndex])
         return self._copyValues(CrossValidatorModel(bestModel, metrics, subModels))
 
     @since("1.4.0")
     def copy(self, extra=None):
         """
         Creates a copy of this instance with a randomly generated uid
         and some extra params. This copies creates a deep copy of
         the embedded paramMap, and copies the embedded and extra parameters over.
 
         :param extra: Extra parameters to copy to the new instance
         :return: Copy of this instance
         """
         if extra is None:
             extra = dict()
         newCV = Params.copy(self, extra)
         if self.isSet(self.estimator):
             newCV.setEstimator(self.getEstimator().copy(extra))
         # estimatorParamMaps remain the same
         if self.isSet(self.evaluator):
             newCV.setEvaluator(self.getEvaluator().copy(extra))
         return newCV
 
     @since("2.3.0")
     def write(self):
         """Returns an MLWriter instance for this ML instance."""
         return JavaMLWriter(self)
 
     @classmethod
     @since("2.3.0")
     def read(cls):
         """Returns an MLReader instance for this class."""
         return JavaMLReader(cls)
 
     @classmethod
     def _from_java(cls, java_stage):
         """
         Given a Java CrossValidator, create and return a Python wrapper of it.
         Used for ML persistence.
         """
 
         estimator, epms, evaluator = super(CrossValidator, cls)._from_java_impl(java_stage)
         numFolds = java_stage.getNumFolds()
         seed = java_stage.getSeed()
         parallelism = java_stage.getParallelism()
         collectSubModels = java_stage.getCollectSubModels()
         # Create a new instance of this stage.
         py_stage = cls(estimator=estimator, estimatorParamMaps=epms, evaluator=evaluator,
                        numFolds=numFolds, seed=seed, parallelism=parallelism,
                        collectSubModels=collectSubModels)
         py_stage._resetUid(java_stage.uid())
         return py_stage
 
     def _to_java(self):
         """
         Transfer this instance to a Java CrossValidator. Used for ML persistence.
 
         :return: Java object equivalent to this instance.
         """
 
         estimator, epms, evaluator = super(CrossValidator, self)._to_java_impl()
 
         _java_obj = JavaParams._new_java_obj("org.apache.spark.ml.tuning.CrossValidator", self.uid)
         _java_obj.setEstimatorParamMaps(epms)
         _java_obj.setEvaluator(evaluator)
         _java_obj.setEstimator(estimator)
         _java_obj.setSeed(self.getSeed())
         _java_obj.setNumFolds(self.getNumFolds())
         _java_obj.setParallelism(self.getParallelism())
         _java_obj.setCollectSubModels(self.getCollectSubModels())
 
         return _java_obj
 
 
 class CrossValidatorModel(Model, _CrossValidatorParams, MLReadable, MLWritable):
     """
 
     CrossValidatorModel contains the model with the highest average cross-validation
     metric across folds and uses this model to transform input data. CrossValidatorModel
     also tracks the metrics for each param map evaluated.
 
     .. versionadded:: 1.4.0
     """
 
     def __init__(self, bestModel, avgMetrics=[], subModels=None):
         super(CrossValidatorModel, self).__init__()
         #: best model from cross validation
         self.bestModel = bestModel
         #: Average cross-validation metrics for each paramMap in
         #: CrossValidator.estimatorParamMaps, in the corresponding order.
         self.avgMetrics = avgMetrics
         #: sub model list from cross validation
         self.subModels = subModels
 
     def _transform(self, dataset):
         return self.bestModel.transform(dataset)
 
     @since("1.4.0")
     def copy(self, extra=None):
         """
         Creates a copy of this instance with a randomly generated uid
         and some extra params. This copies the underlying bestModel,
         creates a deep copy of the embedded paramMap, and
         copies the embedded and extra parameters over.
         It does not copy the extra Params into the subModels.
 
         :param extra: Extra parameters to copy to the new instance
         :return: Copy of this instance
         """
         if extra is None:
             extra = dict()
         bestModel = self.bestModel.copy(extra)
         avgMetrics = self.avgMetrics
         subModels = self.subModels
         return CrossValidatorModel(bestModel, avgMetrics, subModels)
 
     @since("2.3.0")
     def write(self):
         """Returns an MLWriter instance for this ML instance."""
         return JavaMLWriter(self)
 
     @classmethod
     @since("2.3.0")
     def read(cls):
         """Returns an MLReader instance for this class."""
         return JavaMLReader(cls)
 
     @classmethod
     def _from_java(cls, java_stage):
         """
         Given a Java CrossValidatorModel, create and return a Python wrapper of it.
         Used for ML persistence.
         """
         sc = SparkContext._active_spark_context
         bestModel = JavaParams._from_java(java_stage.bestModel())
         avgMetrics = _java2py(sc, java_stage.avgMetrics())
         estimator, epms, evaluator = super(CrossValidatorModel, cls)._from_java_impl(java_stage)
 
         py_stage = cls(bestModel=bestModel, avgMetrics=avgMetrics)._set(estimator=estimator)
         py_stage = py_stage._set(estimatorParamMaps=epms)._set(evaluator=evaluator)
 
         if java_stage.hasSubModels():
             py_stage.subModels = [[JavaParams._from_java(sub_model)
                                    for sub_model in fold_sub_models]
                                   for fold_sub_models in java_stage.subModels()]
 
         py_stage._resetUid(java_stage.uid())
         return py_stage
 
     def _to_java(self):
         """
         Transfer this instance to a Java CrossValidatorModel. Used for ML persistence.
 
         :return: Java object equivalent to this instance.
         """
 
         sc = SparkContext._active_spark_context
         _java_obj = JavaParams._new_java_obj("org.apache.spark.ml.tuning.CrossValidatorModel",
                                              self.uid,
                                              self.bestModel._to_java(),
                                              _py2java(sc, self.avgMetrics))
         estimator, epms, evaluator = super(CrossValidatorModel, self)._to_java_impl()
 
         _java_obj.set("evaluator", evaluator)
         _java_obj.set("estimator", estimator)
         _java_obj.set("estimatorParamMaps", epms)
 
         if self.subModels is not None:
             java_sub_models = [[sub_model._to_java() for sub_model in fold_sub_models]
                                for fold_sub_models in self.subModels]
             _java_obj.setSubModels(java_sub_models)
         return _java_obj
 
 
 class _TrainValidationSplitParams(_ValidatorParams):
     """
     Params for :py:class:`TrainValidationSplit` and :py:class:`TrainValidationSplitModel`.
 
     .. versionadded:: 3.0.0
     """
 
     trainRatio = Param(Params._dummy(), "trainRatio", "Param for ratio between train and\
      validation data. Must be between 0 and 1.", typeConverter=TypeConverters.toFloat)
 
     @since("2.0.0")
     def getTrainRatio(self):
         """
         Gets the value of trainRatio or its default value.
         """
         return self.getOrDefault(self.trainRatio)
 
 
 class TrainValidationSplit(Estimator, _TrainValidationSplitParams, HasParallelism,
                            HasCollectSubModels, MLReadable, MLWritable):
     """
     Validation for hyper-parameter tuning. Randomly splits the input dataset into train and
     validation sets, and uses evaluation metric on the validation set to select the best model.
     Similar to :class:`CrossValidator`, but only splits the set once.
 
     >>> from pyspark.ml.classification import LogisticRegression
     >>> from pyspark.ml.evaluation import BinaryClassificationEvaluator
     >>> from pyspark.ml.linalg import Vectors
     >>> from pyspark.ml.tuning import TrainValidationSplitModel
     >>> import tempfile
     >>> dataset = spark.createDataFrame(
     ...     [(Vectors.dense([0.0]), 0.0),
     ...      (Vectors.dense([0.4]), 1.0),
     ...      (Vectors.dense([0.5]), 0.0),
     ...      (Vectors.dense([0.6]), 1.0),
     ...      (Vectors.dense([1.0]), 1.0)] * 10,
     ...     ["features", "label"]).repartition(1)
     >>> lr = LogisticRegression()
     >>> grid = ParamGridBuilder().addGrid(lr.maxIter, [0, 1]).build()
     >>> evaluator = BinaryClassificationEvaluator()
     >>> tvs = TrainValidationSplit(estimator=lr, estimatorParamMaps=grid, evaluator=evaluator,
     ...     parallelism=1, seed=42)
     >>> tvsModel = tvs.fit(dataset)
     >>> tvsModel.getTrainRatio()
     0.75
     >>> tvsModel.validationMetrics
     [0.5, ...
     >>> path = tempfile.mkdtemp()
     >>> model_path = path + "/model"
     >>> tvsModel.write().save(model_path)
     >>> tvsModelRead = TrainValidationSplitModel.read().load(model_path)
     >>> tvsModelRead.validationMetrics
     [0.5, ...
     >>> evaluator.evaluate(tvsModel.transform(dataset))
     0.833...
 
     .. versionadded:: 2.0.0
     """
 
     @keyword_only
     def __init__(self, estimator=None, estimatorParamMaps=None, evaluator=None, trainRatio=0.75,
                  parallelism=1, collectSubModels=False, seed=None):
         """
         __init__(self, estimator=None, estimatorParamMaps=None, evaluator=None, trainRatio=0.75,\
                  parallelism=1, collectSubModels=False, seed=None)
         """
         super(TrainValidationSplit, self).__init__()
         self._setDefault(trainRatio=0.75, parallelism=1)
         kwargs = self._input_kwargs
         self._set(**kwargs)
 
     @since("2.0.0")
     @keyword_only
     def setParams(self, estimator=None, estimatorParamMaps=None, evaluator=None, trainRatio=0.75,
                   parallelism=1, collectSubModels=False, seed=None):
         """
         setParams(self, estimator=None, estimatorParamMaps=None, evaluator=None, trainRatio=0.75,\
                   parallelism=1, collectSubModels=False, seed=None):
         Sets params for the train validation split.
         """
         kwargs = self._input_kwargs
         return self._set(**kwargs)
 
     @since("2.0.0")
     def setEstimator(self, value):
         """
         Sets the value of :py:attr:`estimator`.
         """
         return self._set(estimator=value)
 
     @since("2.0.0")
     def setEstimatorParamMaps(self, value):
         """
         Sets the value of :py:attr:`estimatorParamMaps`.
         """
         return self._set(estimatorParamMaps=value)
 
     @since("2.0.0")
     def setEvaluator(self, value):
         """
         Sets the value of :py:attr:`evaluator`.
         """
         return self._set(evaluator=value)
 
     @since("2.0.0")
     def setTrainRatio(self, value):
         """
         Sets the value of :py:attr:`trainRatio`.
         """
         return self._set(trainRatio=value)
 
     def setSeed(self, value):
         """
         Sets the value of :py:attr:`seed`.
         """
         return self._set(seed=value)
 
     def setParallelism(self, value):
         """
         Sets the value of :py:attr:`parallelism`.
         """
         return self._set(parallelism=value)
 
     def setCollectSubModels(self, value):
         """
         Sets the value of :py:attr:`collectSubModels`.
         """
         return self._set(collectSubModels=value)
 
     def _fit(self, dataset):
         est = self.getOrDefault(self.estimator)
         epm = self.getOrDefault(self.estimatorParamMaps)
         numModels = len(epm)
         eva = self.getOrDefault(self.evaluator)
         tRatio = self.getOrDefault(self.trainRatio)
         seed = self.getOrDefault(self.seed)
         randCol = self.uid + "_rand"
         df = dataset.select("*", rand(seed).alias(randCol))
         condition = (df[randCol] >= tRatio)
         validation = df.filter(condition).cache()
         train = df.filter(~condition).cache()
 
         subModels = None
         collectSubModelsParam = self.getCollectSubModels()
         if collectSubModelsParam:
             subModels = [None for i in range(numModels)]
 
         tasks = _parallelFitTasks(est, train, eva, validation, epm, collectSubModelsParam)
         pool = ThreadPool(processes=min(self.getParallelism(), numModels))
         metrics = [None] * numModels
         for j, metric, subModel in pool.imap_unordered(lambda f: f(), tasks):
             metrics[j] = metric
             if collectSubModelsParam:
                 subModels[j] = subModel
 
         train.unpersist()
         validation.unpersist()
 
         if eva.isLargerBetter():
             bestIndex = np.argmax(metrics)
         else:
             bestIndex = np.argmin(metrics)
         bestModel = est.fit(dataset, epm[bestIndex])
         return self._copyValues(TrainValidationSplitModel(bestModel, metrics, subModels))
 
     @since("2.0.0")
     def copy(self, extra=None):
         """
         Creates a copy of this instance with a randomly generated uid
         and some extra params. This copies creates a deep copy of
         the embedded paramMap, and copies the embedded and extra parameters over.
 
         :param extra: Extra parameters to copy to the new instance
         :return: Copy of this instance
         """
         if extra is None:
             extra = dict()
         newTVS = Params.copy(self, extra)
         if self.isSet(self.estimator):
             newTVS.setEstimator(self.getEstimator().copy(extra))
         # estimatorParamMaps remain the same
         if self.isSet(self.evaluator):
             newTVS.setEvaluator(self.getEvaluator().copy(extra))
         return newTVS
 
     @since("2.3.0")
     def write(self):
         """Returns an MLWriter instance for this ML instance."""
         return JavaMLWriter(self)
 
     @classmethod
     @since("2.3.0")
     def read(cls):
         """Returns an MLReader instance for this class."""
         return JavaMLReader(cls)
 
     @classmethod
     def _from_java(cls, java_stage):
         """
         Given a Java TrainValidationSplit, create and return a Python wrapper of it.
         Used for ML persistence.
         """
 
         estimator, epms, evaluator = super(TrainValidationSplit, cls)._from_java_impl(java_stage)
         trainRatio = java_stage.getTrainRatio()
         seed = java_stage.getSeed()
         parallelism = java_stage.getParallelism()
         collectSubModels = java_stage.getCollectSubModels()
         # Create a new instance of this stage.
         py_stage = cls(estimator=estimator, estimatorParamMaps=epms, evaluator=evaluator,
                        trainRatio=trainRatio, seed=seed, parallelism=parallelism,
                        collectSubModels=collectSubModels)
         py_stage._resetUid(java_stage.uid())
         return py_stage
 
     def _to_java(self):
         """
         Transfer this instance to a Java TrainValidationSplit. Used for ML persistence.
         :return: Java object equivalent to this instance.
         """
 
         estimator, epms, evaluator = super(TrainValidationSplit, self)._to_java_impl()
 
         _java_obj = JavaParams._new_java_obj("org.apache.spark.ml.tuning.TrainValidationSplit",
                                              self.uid)
         _java_obj.setEstimatorParamMaps(epms)
         _java_obj.setEvaluator(evaluator)
         _java_obj.setEstimator(estimator)
         _java_obj.setTrainRatio(self.getTrainRatio())
         _java_obj.setSeed(self.getSeed())
         _java_obj.setParallelism(self.getParallelism())
         _java_obj.setCollectSubModels(self.getCollectSubModels())
         return _java_obj
 
 
 class TrainValidationSplitModel(Model, _TrainValidationSplitParams, MLReadable, MLWritable):
     """
     Model from train validation split.
 
     .. versionadded:: 2.0.0
     """
 
     def __init__(self, bestModel, validationMetrics=[], subModels=None):
         super(TrainValidationSplitModel, self).__init__()
         #: best model from train validation split
         self.bestModel = bestModel
         #: evaluated validation metrics
         self.validationMetrics = validationMetrics
         #: sub models from train validation split
         self.subModels = subModels
 
     def _transform(self, dataset):
         return self.bestModel.transform(dataset)
 
     @since("2.0.0")
     def copy(self, extra=None):
         """
         Creates a copy of this instance with a randomly generated uid
         and some extra params. This copies the underlying bestModel,
         creates a deep copy of the embedded paramMap, and
         copies the embedded and extra parameters over.
         And, this creates a shallow copy of the validationMetrics.
         It does not copy the extra Params into the subModels.
 
         :param extra: Extra parameters to copy to the new instance
         :return: Copy of this instance
         """
         if extra is None:
             extra = dict()
         bestModel = self.bestModel.copy(extra)
         validationMetrics = list(self.validationMetrics)
         subModels = self.subModels
         return TrainValidationSplitModel(bestModel, validationMetrics, subModels)
 
     @since("2.3.0")
     def write(self):
         """Returns an MLWriter instance for this ML instance."""
         return JavaMLWriter(self)
 
     @classmethod
     @since("2.3.0")
     def read(cls):
         """Returns an MLReader instance for this class."""
         return JavaMLReader(cls)
 
     @classmethod
     def _from_java(cls, java_stage):
         """
         Given a Java TrainValidationSplitModel, create and return a Python wrapper of it.
         Used for ML persistence.
         """
 
         # Load information from java_stage to the instance.
         sc = SparkContext._active_spark_context
         bestModel = JavaParams._from_java(java_stage.bestModel())
         validationMetrics = _java2py(sc, java_stage.validationMetrics())
         estimator, epms, evaluator = super(TrainValidationSplitModel,
                                            cls)._from_java_impl(java_stage)
         # Create a new instance of this stage.
         py_stage = cls(bestModel=bestModel,
                        validationMetrics=validationMetrics)._set(estimator=estimator)
         py_stage = py_stage._set(estimatorParamMaps=epms)._set(evaluator=evaluator)
 
         if java_stage.hasSubModels():
             py_stage.subModels = [JavaParams._from_java(sub_model)
                                   for sub_model in java_stage.subModels()]
 
         py_stage._resetUid(java_stage.uid())
         return py_stage
 
     def _to_java(self):
         """
         Transfer this instance to a Java TrainValidationSplitModel. Used for ML persistence.
         :return: Java object equivalent to this instance.
         """
 
         sc = SparkContext._active_spark_context
         _java_obj = JavaParams._new_java_obj(
             "org.apache.spark.ml.tuning.TrainValidationSplitModel",
             self.uid,
             self.bestModel._to_java(),
             _py2java(sc, self.validationMetrics))
         estimator, epms, evaluator = super(TrainValidationSplitModel, self)._to_java_impl()
 
         _java_obj.set("evaluator", evaluator)
         _java_obj.set("estimator", estimator)
         _java_obj.set("estimatorParamMaps", epms)
 
         if self.subModels is not None:
             java_sub_models = [sub_model._to_java() for sub_model in self.subModels]
             _java_obj.setSubModels(java_sub_models)
 
         return _java_obj
 
 
 if __name__ == "__main__":
     import doctest
 
     from pyspark.sql import SparkSession
     globs = globals().copy()
 
     # The small batch size here ensures that we see multiple batches,
     # even in these small test examples:
     spark = SparkSession.builder\
         .master("local[2]")\
         .appName("ml.tuning tests")\
         .getOrCreate()
     sc = spark.sparkContext
     globs['sc'] = sc
     globs['spark'] = spark
     (failure_count, test_count) = doctest.testmod(globs=globs, optionflags=doctest.ELLIPSIS)
     spark.stop()
     if failure_count:
         sys.exit(-1)

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