exp.py

# Copyright [2024] Expedia, Inc.
#
# Licensed 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.

# pylint: disable=unused-argument
# pylint: disable=invalid-name
# pylint: disable=too-many-ancestors
# pylint: disable=no-member
from typing import List, Optional

import keras
import pyspark.sql.functions as F
from pyspark import keyword_only
from pyspark.sql import DataFrame
from pyspark.sql.types import DataType, DoubleType, FloatType

from kamae.keras.core.backend import ALL_BACKENDS
from kamae.keras.core.layers import ExpLayer
from kamae.spark.params import SingleInputSingleOutputParams
from kamae.spark.utils import single_input_single_output_scalar_transform

from .base import BaseTransformer


class ExpTransformer(
    BaseTransformer,
    SingleInputSingleOutputParams,
):
    """
    exp value Spark Transformer for use in Spark pipelines.
    This transformer applies exp(x) operation to the input.
    """

    supported_backends = ALL_BACKENDS
    jit_compatible = True

    @keyword_only
    def __init__(
        self,
        inputCol: Optional[str] = None,
        outputCol: Optional[str] = None,
        inputDtype: Optional[str] = None,
        outputDtype: Optional[str] = None,
        layerName: Optional[str] = None,
    ) -> None:
        """
        Initializes an ExpTransformer transformer.

        :param inputCol: Input column name.
        :param outputCol: Output column name.
        :param inputDtype: Input data type to cast input column to before
        transforming.
        :param outputDtype: Output data type to cast the output column to after
        transforming.
        :param layerName: Name of the layer. Used as the name of the Keras layer
        in the keras model. If not set, we use the uid of the Spark transformer.
        :returns: None - class instantiated.
        """
        super().__init__()
        kwargs = self._input_kwargs
        self.setParams(**kwargs)

    @property
    def compatible_dtypes(self) -> Optional[List[DataType]]:
        """
        List of compatible data types for the layer.
        If the computation can be performed on any data type, return None.

        :returns: List of compatible data types for the layer.
        """
        return [FloatType(), DoubleType()]

    def _transform(self, dataset: DataFrame) -> DataFrame:
        """
        Transforms the input dataset. Creates a new column with name `outputCol`,
        which applies exp(`inputCol`).

        :param dataset: Pyspark dataframe to transform.
        :returns: Transformed pyspark dataframe.
        """
        input_datatype = self.get_column_datatype(
            dataset=dataset, column_name=self.getInputCol()
        )
        output_col = single_input_single_output_scalar_transform(
            input_col=F.col(self.getInputCol()),
            input_col_datatype=input_datatype,
            func=lambda x: F.exp(x),
        )
        return dataset.withColumn(self.getOutputCol(), output_col)

    def get_keras_layer(self) -> keras.layers.Layer:
        """
        Gets the Keras layer for the exp value transformer.

        :returns: Keras layer with name equal to the layerName parameter that
         performs an exp value operation.
        """
        return ExpLayer(
            name=self.getLayerName(),
            input_dtype=self.getInputKerasDtype(),
            output_dtype=self.getOutputKerasDtype(),
        )