[DOC] Adds documentation to the abstract evaluator (#160)

* DOC_153

* Changes from Ravin

* [FIX] improve clarity of msg in commit

autoPyTorch/evaluation/abstract_evaluator.py

@@ -262,13 +262,81 @@ def send_warnings_to_log(message, category, filename, lineno,
 
 
 class AbstractEvaluator(object):
+    """
+    This method defines the interface that pipeline evaluators should follow, when
+    interacting with SMAC through ExecuteTaFuncWithQueue.
+
+    An evaluator is an object that:
+        + constructs a pipeline (i.e. a classification or regression estimator) for a given
+          pipeline_config and run settings (budget, seed)
+        + Fits and trains this pipeline (TrainEvaluator) or tests a given
+          configuration (TestEvaluator)
+
+    The provided configuration determines the type of pipeline created. For more
+    details, please read the get_pipeline() method.
+
+    Attributes:
+        backend (Backend):
+            An object that allows interaction with the disk storage. In particular, allows to
+            access the train and test datasets
+        queue (Queue):
+            Each worker available will instantiate an evaluator, and after completion,
+            it will append the result to a multiprocessing queue
+        metric (autoPyTorchMetric):
+            A scorer object that is able to evaluate how good a pipeline was fit. It
+            is a wrapper on top of the actual score method (a wrapper on top of
+            scikit-learn accuracy for example) that formats the predictions accordingly.
+        budget: (float):
+            The amount of epochs/time a configuration is allowed to run.
+        budget_type  (str):
+            The budget type. Currently, only epoch and time are allowed.
+        pipeline_config (Optional[Dict[str, Any]]):
+            Defines the content of the pipeline being evaluated. For example, it
+            contains pipeline specific settings like logging name, or whether or not
+            to use tensorboard.
+        configuration (Union[int, str, Configuration]):
+            Determines the pipeline to be constructed. A dummy estimator is created for
+            integer configurations, a traditional machine learning pipeline is created
+            for string based configuration, and NAS is performed when a configuration
+            object is passed.
+        seed (int):
+            A integer that allows for reproducibility of results
+        output_y_hat_optimization (bool):
+            Whether this worker should output the target predictions, so that they are
+            stored on disk. Fundamentally, the resampling strategy might shuffle the
+            Y_train targets, so we store the split in order to re-use them for ensemble
+            selection.
+        num_run (Optional[int]):
+            An identifier of the current configuration being fit. This number is unique per
+            configuration.
+        include (Optional[Dict[str, Any]]):
+            An optional dictionary to include components of the pipeline steps.
+        exclude (Optional[Dict[str, Any]]):
+            An optional dictionary to exclude components of the pipeline steps.
+        disable_file_output (Union[bool, List[str]]):
+            By default, the model, it's predictions and other metadata is stored on disk
+            for each finished configuration. This argument allows the user to skip
+            saving certain file type, for example the model, from being written to disk.
+        init_params (Optional[Dict[str, Any]]):
+            Optional argument that is passed to each pipeline step. It is the equivalent of
+            kwargs for the pipeline steps.
+        logger_port (Optional[int]):
+            Logging is performed using a socket-server scheme to be robust against many
+            parallel entities that want to write to the same file. This integer states the
+            socket port for the communication channel.
+            If None is provided, the logging.handlers.DEFAULT_TCP_LOGGING_PORT is used.
+        all_supported_metrics  (bool):
+            Whether all supported metrics should be calculated for every configuration.
+        search_space_updates (Optional[HyperparameterSearchSpaceUpdates]):
+            An object used to fine tune the hyperparameter search space of the pipeline
+    """
     def __init__(self, backend: Backend,
                  queue: Queue,
                  metric: autoPyTorchMetric,
                  budget: float,
+                 configuration: Union[int, str, Configuration],
                  budget_type: str = None,
                  pipeline_config: Optional[Dict[str, Any]] = None,
-                 configuration: Optional[Configuration] = None,
                  seed: int = 1,
                  output_y_hat_optimization: bool = True,
                  num_run: Optional[int] = None,
@@ -408,6 +476,23 @@ def __init__(self, backend: Backend,
         self.logger.debug("Search space updates :{}".format(self.search_space_updates))
 
     def _get_pipeline(self) -> BaseEstimator:
+        """
+        Implements a pipeline object based on the self.configuration attribute.
+        int: A dummy classifier/dummy regressor is created. This estimator serves
+             as a baseline model to ignore all models that perform worst than this
+             fixed estimator. Also, in the worst case scenario, this is the final
+             estimator created (for instance, in case not enough memory was allocated).
+        str: A pipeline with traditional classifiers like random forest, SVM, etc is created,
+             as the configuration will contain an estimator name defining the configuration
+             to use, for example 'RandomForest'
+        Configuration: A pipeline object matching this configuration is created. This
+             is the case of neural architecture search, where different backbones
+             and head can be passed in the form of a configuration object.
+
+        Returns
+            pipeline (BaseEstimator):
+                A scikit-learn compliant pipeline which is not yet fit to the data.
+        """
         assert self.pipeline_class is not None, "Can't return pipeline, pipeline_class not initialised"
         if isinstance(self.configuration, int):
             pipeline = self.pipeline_class(config=self.configuration,
@@ -436,6 +521,15 @@ def _loss(self, y_true: np.ndarray, y_hat: np.ndarray) -> Dict[str, float]:
         The calculate_loss internally translate a score function to
         a minimization problem
 
+        Args:
+            y_true (np.ndarray):
+                The expect labels given by the original dataset
+            y_hat (np.ndarray):
+                The prediction of the current pipeline being fit
+        Returns:
+            (Dict[str, float]):
+                A dictionary with metric_name -> metric_loss, for every
+                supported metric
         """
 
         if isinstance(self.configuration, int):
@@ -461,7 +555,39 @@ def finish_up(self, loss: Dict[str, float], train_loss: Dict[str, float],
         * saving the files for the ensembles_statistics
         * generate output for SMAC
         We use it as the signal handler so we can recycle the code for the
-        normal usecase and when the runsolver kills us here :)"""
+        normal usecase and when the runsolver kills us here :)
+
+        Args:
+            loss (Dict[str, float]):
+                The optimization loss, calculated on the validation set. This will
+                be the cost used in SMAC
+            train_loss (Dict[str, float]):
+                The train loss, calculated on the train set
+            opt_pred (np.ndarray):
+                The predictions on the validation set. This validation set is created
+                from the resampling strategy
+            valid_pred (Optional[np.ndarray]):
+                Predictions on a user provided validation set
+            test_pred (Optional[np.ndarray]):
+                Predictions on a user provided test set
+            additional_run_info (Optional[Dict]):
+                A dictionary with additional run information, like duration or
+                the crash error msg, if any.
+            file_output (bool):
+                Whether or not this pipeline should output information to disk
+            status (StatusType)
+                The status of the run, following SMAC StatusType syntax.
+
+        Returns:
+            duration (float):
+                The elapsed time of the training of this evaluator
+            loss (float):
+                The optimization loss of this run
+            seed (int):
+                The seed used while fitting the pipeline
+            additional_info (Dict):
+                Additional run information, like train/test loss
+        """
 
         self.duration = time.time() - self.starttime
 
@@ -508,6 +634,25 @@ def calculate_auxiliary_losses(
             Y_valid_pred: np.ndarray,
             Y_test_pred: np.ndarray,
     ) -> Tuple[Optional[float], Optional[float]]:
+        """
+        A helper function to calculate the performance estimate of the
+        current pipeline in the user provided validation/test set.
+
+        Args:
+            Y_valid_pred (np.ndarray):
+                predictions on a validation set provided by the user,
+                matching self.y_valid
+            Y_test_pred (np.ndarray):
+                predictions on a test set provided by the user,
+                matching self.y_test
+        Returns:
+            validation_loss (Optional[float]):
+                The validation loss under the optimization metric
+                stored in self.metric
+            test_loss (Optional[float]]):
+                The test loss under the optimization metric
+                stored in self.metric
+        """
 
         validation_loss: Optional[float] = None
 
@@ -530,6 +675,31 @@ def file_output(
             Y_valid_pred: np.ndarray,
             Y_test_pred: np.ndarray
     ) -> Tuple[Optional[float], Dict]:
+        """
+        This method decides what file outputs are written to disk.
+
+        It is also the interface to the backed save_numrun_to_dir
+        which stores all the pipeline related information to a single
+        directory for easy identification of the current run.
+
+        Args:
+            Y_optimization_pred (np.ndarray):
+                The pipeline predictions on the validation set internally created
+                from self.y_train
+            Y_valid_pred (np.ndarray):
+                The pipeline predictions on the user provided validation set,
+                which should match self.y_valid
+            Y_test_pred (np.ndarray):
+                The pipeline predictions on the user provided test set,
+                which should match self.y_test
+        Returns:
+            loss (Optional[float]):
+                A loss in case the run failed to store files to
+                disk
+            error_dict (Dict):
+                A dictionary with an error that explains why a run
+                was not successfully stored to disk.
+        """
         # Abort if self.Y_optimization is None
         # self.Y_optimization can be None if we use partial-cv, then,
         # obviously no output should be saved.
@@ -624,6 +794,23 @@ def file_output(
 
     def _predict_proba(self, X: np.ndarray, pipeline: BaseEstimator,
                        Y_train: Optional[np.ndarray] = None) -> np.ndarray:
+        """
+        A wrapper function to handle the prediction of classification tasks.
+        It also makes sure that the predictions has the same dimensionality
+        as the expected labels
+
+        Args:
+            X (np.ndarray):
+                A set of features to feed to the pipeline
+            pipeline (BaseEstimator):
+                A model that will take the features X return a prediction y
+                This pipeline must be a classification estimator that supports
+                the predict_proba method.
+            Y_train (Optional[np.ndarray]):
+        Returns:
+            (np.ndarray):
+                The predictions of pipeline for the given features X
+        """
         @no_type_check
         def send_warnings_to_log(message, category, filename, lineno,
                                  file=None, line=None):
@@ -640,6 +827,24 @@ def send_warnings_to_log(message, category, filename, lineno,
 
     def _predict_regression(self, X: np.ndarray, pipeline: BaseEstimator,
                             Y_train: Optional[np.ndarray] = None) -> np.ndarray:
+        """
+        A wrapper function to handle the prediction of regression tasks.
+        It is a wrapper to provide the same interface to _predict_proba
+
+        Regression predictions expects an unraveled dimensionality.
+        To comply with scikit-learn VotingRegressor requirement, if the estimator
+        predicts a (N,) shaped array, it is converted to (N, 1)
+
+        Args:
+            X (np.ndarray):
+                A set of features to feed to the pipeline
+            pipeline (BaseEstimator):
+                A model that will take the features X return a prediction y
+            Y_train (Optional[np.ndarray]):
+        Returns:
+            (np.ndarray):
+                The predictions of pipeline for the given features X
+        """
         @no_type_check
         def send_warnings_to_log(message, category, filename, lineno,
                                  file=None, line=None):
@@ -658,6 +863,20 @@ def send_warnings_to_log(message, category, filename, lineno,
 
     def _ensure_prediction_array_sizes(self, prediction: np.ndarray,
                                        Y_train: np.ndarray) -> np.ndarray:
+        """
+        This method formats a prediction to match the dimensionality of the provided
+        labels (Y_train). This should be used exclusively for classification tasks
+
+        Args:
+            prediction (np.ndarray):
+                The un-formatted predictions of a pipeline
+            Y_train (np.ndarray):
+                The labels from the dataset to give an intuition of the expected
+                predictions dimensionality
+        Returns:
+            (np.ndarray):
+                The formatted prediction
+        """
         assert self.datamanager.num_classes is not None, "Called function on wrong task"
         num_classes: int = self.datamanager.num_classes