# Copyright 2016 The TensorFlow Authors. All Rights Reserved.
#
# 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,
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# ==============================================================================

"""`Evaluable` interface."""

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import abc


class Evaluable(object):
  """Interface for objects that are evaluatable by, e.g., `Experiment`.
  """
  __metaclass__ = abc.ABCMeta

  @abc.abstractproperty
  def model_dir(self):
    """Returns a path in which the eval process will look for checkpoints."""
    raise NotImplementedError

  @abc.abstractmethod
  def evaluate(self,
               x=None,
               y=None,
               input_fn=None,
               feed_fn=None,
               batch_size=None,
               steps=None,
               metrics=None,
               name=None,
               checkpoint_path=None,
               hooks=None):
    """Evaluates given model with provided evaluation data.

    Stop conditions - we evaluate on the given input data until one of the
    following:
    - If `steps` is provided, and `steps` batches of size `batch_size` are
    processed.
    - If `input_fn` is provided, and it raises an end-of-input
    exception (`OutOfRangeError` or `StopIteration`).
    - If `x` is provided, and all items in `x` have been processed.

    The return value is a dict containing the metrics specified in `metrics`, as
    well as an entry `global_step` which contains the value of the global step
    for which this evaluation was performed.

    Args:
      x: Matrix of shape [n_samples, n_features...] or dictionary of many matrices
         containing the input samples for fitting the model. Can be iterator that returns
         arrays of features or dictionary of array of features. If set, `input_fn` must
         be `None`.
      y: Vector or matrix [n_samples] or [n_samples, n_outputs] containing the
         label values (class labels in classification, real numbers in
         regression) or dictionary of multiple vectors/matrices. Can be iterator
         that returns array of targets or dictionary of array of targets. If set,
         `input_fn` must be `None`. Note: For classification, label values must
         be integers representing the class index (i.e. values from 0 to
         n_classes-1).
      input_fn: Input function returning a tuple of:
          features - Dictionary of string feature name to `Tensor` or `Tensor`.
          labels - `Tensor` or dictionary of `Tensor` with labels.
        If input_fn is set, `x`, `y`, and `batch_size` must be `None`. If
        `steps` is not provided, this should raise `OutOfRangeError` or
        `StopIteration` after the desired amount of data (e.g., one epoch) has
        been provided. See "Stop conditions" above for specifics.
      feed_fn: Function creating a feed dict every time it is called. Called
        once per iteration. Must be `None` if `input_fn` is provided.
      batch_size: minibatch size to use on the input, defaults to first
        dimension of `x`, if specified. Must be `None` if `input_fn` is
        provided.
      steps: Number of steps for which to evaluate model. If `None`, evaluate
        until `x` is consumed or `input_fn` raises an end-of-input exception.
        See "Stop conditions" above for specifics.
      metrics: Dict of metrics to run. If None, the default metric functions
        are used; if {}, no metrics are used. Otherwise, `metrics` should map
        friendly names for the metric to a `MetricSpec` object defining which
        model outputs to evaluate against which labels with which metric
        function.

        Metric ops should support streaming, e.g., returning `update_op` and
        `value` tensors. For example, see the options defined in
        `../../../metrics/python/ops/metrics_ops.py`.
      name: Name of the evaluation if user needs to run multiple evaluations on
        different data sets, such as on training data vs test data.
      checkpoint_path: Path of a specific checkpoint to evaluate. If `None`, the
        latest checkpoint in `model_dir` is used.
      hooks: List of `SessionRunHook` subclass instances. Used for callbacks
        inside the evaluation call.

    Returns:
      Returns `dict` with evaluation results.
    """
    raise NotImplementedError
