Github user mengxr commented on a diff in the pull request:

    https://github.com/apache/spark/pull/5601#discussion_r28750129
  
    --- Diff: python/pyspark/ml/tuning.py ---
    @@ -0,0 +1,84 @@
    +#
    +# 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.
    +#
    +
    +__all__ = ['ParamGridBuilder']
    +
    +
    +class ParamGridBuilder(object):
    +    """
    +    Builder for a param grid used in grid search-based model selection.
    +    """
    +
    +    def __init__(self):
    +        self._param_grid = {}
    +
    +    def addGrid(self, param, values):
    +        """
    +        Sets the given parameters in this grid to fixed values.
    +        """
    +        self._param_grid[param] = values
    +
    +    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])
    +
    +    def build(self):
    +        """
    +        Builds and returns all combinations of parameters specified
    +        by the param grid.
    +        """
    +        param_maps = [{}]
    +        for (param, values) in self._param_grid.items():
    +            new_param_maps = []
    +            for value in values:
    +                for old_map in param_maps:
    +                    copied_map = old_map.copy()
    +                    copied_map[param] = value
    +                    new_param_maps.append(copied_map)
    +            param_maps = new_param_maps
    +
    +        return param_maps
    +
    +
    +if __name__ == "__main__":
    +    grid_test = ParamGridBuilder()
    +    from classification import LogisticRegression
    +    lr = LogisticRegression()
    +    grid_test.addGrid(lr.regParam, [1.0, 2.0, 3.0])
    +    grid_test.addGrid(lr.maxIter, [1, 5])
    --- End diff --
    
    Use builder pattern.


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