tf.compat.v1.estimator.tpu.TPUEstimator

View source on GitHub

Estimator with TPU support.

Inherits From: Estimator

tf.compat.v1.estimator.tpu.TPUEstimator(
    model_fn=None, model_dir=None, config=None, params=None, use_tpu=True,
    train_batch_size=None, eval_batch_size=None, predict_batch_size=None,
    batch_axis=None, eval_on_tpu=True, export_to_tpu=True, export_to_cpu=True,
    warm_start_from=None, embedding_config_spec=None,
    export_saved_model_api_version=ExportSavedModelApiVersion.V1
)

TPUEstimator also supports training on CPU and GPU. You don't need to define a separate tf.estimator.Estimator.

TPUEstimator handles many of the details of running on TPU devices, such as replicating inputs and models for each core, and returning to host periodically to run hooks.

TPUEstimator transforms a global batch size in params to a per-shard batch size when calling the input_fn and model_fn. Users should specify global batch size in constructor, and then get the batch size for each shard in input_fn and model_fn by params['batch_size'].

Evaluation

model_fn should return TPUEstimatorSpec, which expects the eval_metrics for TPU evaluation. If eval_on_tpu is False, the evaluation will execute on CPU or GPU; in this case the following discussion on TPU evaluation does not apply.

TPUEstimatorSpec.eval_metrics is a tuple of metric_fn and tensors, where tensors could be a list of any nested structure of Tensors (See TPUEstimatorSpec for details). metric_fn takes the tensors and returns a dict from metric string name to the result of calling a metric function, namely a (metric_tensor, update_op) tuple.

One can set use_tpu to False for testing. All training, evaluation, and predict will be executed on CPU. input_fn and model_fn will receive train_batch_size or eval_batch_size unmodified as params['batch_size'].

Current limitations:

  1. TPU evaluation only works on a single host (one TPU worker) except BROADCAST mode.

  2. input_fn for evaluation should NOT raise an end-of-input exception (OutOfRangeError or StopIteration). And all evaluation steps and all batches should have the same size.

Example (MNIST):

# The metric Fn which runs on CPU.
def metric_fn(labels, logits):
  predictions = tf.argmax(logits, 1)
  return {
    'accuracy': tf.compat.v1.metrics.precision(
        labels=labels, predictions=predictions),
  }

# Your model Fn which runs on TPU (eval_metrics is list in this example)
def model_fn(features, labels, mode, config, params):
  ...
  logits = ...

  if mode = tf.estimator.ModeKeys.EVAL:
    return tpu_estimator.TPUEstimatorSpec(
        mode=mode,
        loss=loss,
        eval_metrics=(metric_fn, [labels, logits]))

# or specify the eval_metrics tensors as dict.
def model_fn(features, labels, mode, config, params):
  ...
  final_layer_output = ...

  if mode = tf.estimator.ModeKeys.EVAL:
    return tpu_estimator.TPUEstimatorSpec(
        mode=mode,
        loss=loss,
        eval_metrics=(metric_fn, {
            'labels': labels,
            'logits': final_layer_output,
        }))

Prediction

Prediction on TPU is an experimental feature to support large batch inference. It is not designed for latency-critical system. In addition, due to some usability issues, for prediction with small dataset, CPU .predict, i.e., creating a new TPUEstimator instance with use_tpu=False, might be more convenient.

Note: In contrast to TPU training/evaluation, the input_fn for prediction should raise an end-of-input exception (OutOfRangeError or StopIteration), which serves as the stopping signal to TPUEstimator. To be precise, the ops created by input_fn produce one batch of the data. The predict() API processes one batch at a time. When reaching the end of the data source, an end-of-input exception should be raised by one of these operations. The user usually does not need to do this manually. As long as the dataset is not repeated forever, the tf.data API will raise an end-of-input exception automatically after the last batch has been produced.

Note: Estimator.predict returns a Python generator. Please consume all the data from the generator so that TPUEstimator can shutdown the TPU system properly for user.

Current limitations:

  1. TPU prediction only works on a single host (one TPU worker).

  2. input_fn must return a Dataset instance rather than features. In fact, .train() and .evaluate() also support Dataset as return value.

Example (MNIST):

height = 32
width = 32
total_examples = 100

def predict_input_fn(params):
  batch_size = params['batch_size']

  images = tf.random.uniform(
      [total_examples, height, width, 3], minval=-1, maxval=1)

  dataset = tf.data.Dataset.from_tensor_slices(images)
  dataset = dataset.map(lambda images: {'image': images})

  dataset = dataset.batch(batch_size)
  return dataset

def model_fn(features, labels, params, mode):
   # Generate predictions, called 'output', from features['image']

  if mode == tf.estimator.ModeKeys.PREDICT:
    return tf.contrib.tpu.TPUEstimatorSpec(
        mode=mode,
        predictions={
            'predictions': output,
            'is_padding': features['is_padding']
        })

tpu_est = TPUEstimator(
    model_fn=model_fn,
    ...,
    predict_batch_size=16)

# Fully consume the generator so that TPUEstimator can shutdown the TPU
# system.
for item in tpu_est.predict(input_fn=input_fn):
  # Filter out item if the `is_padding` is 1.
  # Process the 'predictions'

Exporting

export_saved_model exports 2 metagraphs, one with saved_model.SERVING, and another with saved_model.SERVING and saved_model.TPU tags. At serving time, these tags are used to select the appropriate metagraph to load.

Before running the graph on TPU, the TPU system needs to be initialized. If TensorFlow Serving model-server is used, this is done automatically. If not, please use session.run(tpu.initialize_system()).

There are two versions of the API: ExportSavedModelApiVersion.V1 and V2.

In V1, the exported CPU graph is model_fn as it is. The exported TPU graph wraps tpu.rewrite() and TPUPartitionedCallOp around model_fn so model_fn is on TPU by default. To place ops on CPU, tpu.outside_compilation(host_call, logits) can be used.

Example:

def model_fn(features, labels, mode, config, params):
  ...
  logits = ...
  export_outputs = {
    'logits': export_output_lib.PredictOutput(
      {'logits': logits})
  }

  def host_call(logits):
    class_ids = math_ops.argmax(logits)
    classes = string_ops.as_string(class_ids)
    export_outputs['classes'] =
      export_output_lib.ClassificationOutput(classes=classes)

  tpu.outside_compilation(host_call, logits)

  ...

In V2, export_saved_model() sets up params['use_tpu'] flag to let the user know if the code is exporting to TPU (or not). When params['use_tpu'] is True, users need to call tpu.rewrite(), TPUPartitionedCallOp and/or batch_function(). Alternatively use inference_on_tpu() which is a convenience wrapper of the three.

def model_fn(features, labels, mode, config, params):
    ...
    # This could be some pre-processing on CPU like calls to input layer with
    # embedding columns.
    x2 = features['x'] * 2

    def computation(input_tensor):
      return layers.dense(
          input_tensor, 1, kernel_initializer=init_ops.zeros_initializer())

    inputs = [x2]
    if params['use_tpu']:
      predictions = array_ops.identity(
          tpu_estimator.inference_on_tpu(computation, inputs,
          num_batch_threads=1, max_batch_size=2, batch_timeout_micros=100),
          name='predictions')
    else:
      predictions = array_ops.identity(
          computation(*inputs), name='predictions')
    key = signature_constants.DEFAULT_SERVING_SIGNATURE_DEF_KEY
    export_outputs = {
        key: export_lib.PredictOutput({'prediction': predictions})
    }
    ...

TIP: V2 is recommended as it is more flexible (eg: batching, etc).

Args:

Attributes:

Raises:

Methods

eval_dir

View source

eval_dir(
    name=None
)

Shows the directory name where evaluation metrics are dumped.

Args:

Returns:

A string which is the path of directory contains evaluation metrics.

evaluate

View source

evaluate(
    input_fn, steps=None, hooks=None, checkpoint_path=None, name=None
)

Evaluates the model given evaluation data input_fn.

For each step, calls input_fn, which returns one batch of data. Evaluates until: - steps batches are processed, or - input_fn raises an end-of-input exception (tf.errors.OutOfRangeError or StopIteration).

Args:

Returns:

A dict containing the evaluation metrics specified in model_fn keyed by name, as well as an entry global_step which contains the value of the global step for which this evaluation was performed. For canned estimators, the dict contains the loss (mean loss per mini-batch) and the average_loss (mean loss per sample). Canned classifiers also return the accuracy. Canned regressors also return the label/mean and the prediction/mean.

Raises:

experimental_export_all_saved_models

View source

experimental_export_all_saved_models(
    export_dir_base, input_receiver_fn_map, assets_extra=None, as_text=False,
    checkpoint_path=None
)

Exports a SavedModel with tf.MetaGraphDefs for each requested mode.

For each mode passed in via the input_receiver_fn_map, this method builds a new graph by calling the input_receiver_fn to obtain feature and label Tensors. Next, this method calls the Estimator's model_fn in the passed mode to generate the model graph based on those features and labels, and restores the given checkpoint (or, lacking that, the most recent checkpoint) into the graph. Only one of the modes is used for saving variables to the SavedModel (order of preference: tf.estimator.ModeKeys.TRAIN, tf.estimator.ModeKeys.EVAL, then tf.estimator.ModeKeys.PREDICT), such that up to three tf.MetaGraphDefs are saved with a single set of variables in a single SavedModel directory.

For the variables and tf.MetaGraphDefs, a timestamped export directory below export_dir_base, and writes a SavedModel into it containing the tf.MetaGraphDef for the given mode and its associated signatures.

For prediction, the exported MetaGraphDef will provide one SignatureDef for each element of the export_outputs dict returned from the model_fn, named using the same keys. One of these keys is always tf.saved_model.signature_constants.DEFAULT_SERVING_SIGNATURE_DEF_KEY, indicating which signature will be served when a serving request does not specify one. For each signature, the outputs are provided by the corresponding tf.estimator.export.ExportOutputs, and the inputs are always the input receivers provided by the serving_input_receiver_fn.

For training and evaluation, the train_op is stored in an extra collection, and loss, metrics, and predictions are included in a SignatureDef for the mode in question.

Extra assets may be written into the SavedModel via the assets_extra argument. This should be a dict, where each key gives a destination path (including the filename) relative to the assets.extra directory. The corresponding value gives the full path of the source file to be copied. For example, the simple case of copying a single file without renaming it is specified as {'my_asset_file.txt': '/path/to/my_asset_file.txt'}.

Args:

Returns:

The string path to the exported directory.

Raises:

export_saved_model

View source

export_saved_model(
    export_dir_base, serving_input_receiver_fn, assets_extra=None, as_text=False,
    checkpoint_path=None, experimental_mode=ModeKeys.PREDICT
)

Exports inference graph as a SavedModel into the given dir.

For a detailed guide, see Using SavedModel with Estimators.

This method builds a new graph by first calling the serving_input_receiver_fn to obtain feature Tensors, and then calling this Estimator's model_fn to generate the model graph based on those features. It restores the given checkpoint (or, lacking that, the most recent checkpoint) into this graph in a fresh session. Finally it creates a timestamped export directory below the given export_dir_base, and writes a SavedModel into it containing a single tf.MetaGraphDef saved from this session.

The exported MetaGraphDef will provide one SignatureDef for each element of the export_outputs dict returned from the model_fn, named using the same keys. One of these keys is always tf.saved_model.signature_constants.DEFAULT_SERVING_SIGNATURE_DEF_KEY, indicating which signature will be served when a serving request does not specify one. For each signature, the outputs are provided by the corresponding tf.estimator.export.ExportOutputs, and the inputs are always the input receivers provided by the serving_input_receiver_fn.

Extra assets may be written into the SavedModel via the assets_extra argument. This should be a dict, where each key gives a destination path (including the filename) relative to the assets.extra directory. The corresponding value gives the full path of the source file to be copied. For example, the simple case of copying a single file without renaming it is specified as {'my_asset_file.txt': '/path/to/my_asset_file.txt'}.

The experimental_mode parameter can be used to export a single train/eval/predict graph as a SavedModel. See experimental_export_all_saved_models for full docs.

Args:

Returns:

The string path to the exported directory.

Raises:

export_savedmodel

View source

export_savedmodel(
    export_dir_base, serving_input_receiver_fn, assets_extra=None, as_text=False,
    checkpoint_path=None, strip_default_attrs=False
)

Exports inference graph as a SavedModel into the given dir. (deprecated)

Warning: THIS FUNCTION IS DEPRECATED. It will be removed in a future version. Instructions for updating: This function has been renamed, use export_saved_model instead.

For a detailed guide, see Using SavedModel with Estimators.

This method builds a new graph by first calling the serving_input_receiver_fn to obtain feature Tensors, and then calling this Estimator's model_fn to generate the model graph based on those features. It restores the given checkpoint (or, lacking that, the most recent checkpoint) into this graph in a fresh session. Finally it creates a timestamped export directory below the given export_dir_base, and writes a SavedModel into it containing a single tf.MetaGraphDef saved from this session.

The exported MetaGraphDef will provide one SignatureDef for each element of the export_outputs dict returned from the model_fn, named using the same keys. One of these keys is always tf.saved_model.signature_constants.DEFAULT_SERVING_SIGNATURE_DEF_KEY, indicating which signature will be served when a serving request does not specify one. For each signature, the outputs are provided by the corresponding tf.estimator.export.ExportOutputs, and the inputs are always the input receivers provided by the serving_input_receiver_fn.

Extra assets may be written into the SavedModel via the assets_extra argument. This should be a dict, where each key gives a destination path (including the filename) relative to the assets.extra directory. The corresponding value gives the full path of the source file to be copied. For example, the simple case of copying a single file without renaming it is specified as {'my_asset_file.txt': '/path/to/my_asset_file.txt'}.

Args:

Returns:

The string path to the exported directory.

Raises:

get_variable_names

View source

get_variable_names()

Returns list of all variable names in this model.

Returns:

List of names.

Raises:

get_variable_value

View source

get_variable_value(
    name
)

Returns value of the variable given by name.

Args:

Returns:

Numpy array - value of the tensor.

Raises:

latest_checkpoint

View source

latest_checkpoint()

Finds the filename of the latest saved checkpoint file in model_dir.

Returns:

The full path to the latest checkpoint or None if no checkpoint was found.

predict

View source

predict(
    input_fn, predict_keys=None, hooks=None, checkpoint_path=None,
    yield_single_examples=True
)

Yields predictions for given features.

Please note that interleaving two predict outputs does not work. See: issue/20506

Args:

Yields:

Evaluated values of predictions tensors.

Raises:

train

View source

train(
    input_fn, hooks=None, steps=None, max_steps=None, saving_listeners=None
)

Trains a model given training data input_fn.

Args:

Returns:

self, for chaining.

Raises: