tf.keras.metrics.Metric

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Class Metric

Encapsulates metric logic and state.

Inherits From: Layer

Aliases:

Usage:

m = SomeMetric(...)
for input in ...:
  m.update_state(input)
print('Final result: ', m.result().numpy())

Usage with tf.keras API:

model = tf.keras.Sequential()
model.add(tf.keras.layers.Dense(64, activation='relu'))
model.add(tf.keras.layers.Dense(64, activation='relu'))
model.add(tf.keras.layers.Dense(10, activation='softmax'))

model.compile(optimizer=tf.compat.v1.train.RMSPropOptimizer(0.01),
              loss=tf.keras.losses.categorical_crossentropy,
              metrics=[tf.keras.metrics.CategoricalAccuracy()])

data = np.random.random((1000, 32))
labels = np.random.random((1000, 10))

dataset = tf.data.Dataset.from_tensor_slices((data, labels))
dataset = dataset.batch(32)
dataset = dataset.repeat()

model.fit(dataset, epochs=10, steps_per_epoch=30)

To be implemented by subclasses: * __init__(): All state variables should be created in this method by calling self.add_weight() like: self.var = self.add_weight(...) * update_state(): Has all updates to the state variables like: self.var.assign_add(...). * result(): Computes and returns a value for the metric from the state variables.

Example subclass implementation:

class BinaryTruePositives(tf.keras.metrics.Metric):

  def __init__(self, name='binary_true_positives', **kwargs):
    super(BinaryTruePositives, self).__init__(name=name, **kwargs)
    self.true_positives = self.add_weight(name='tp', initializer='zeros')

  def update_state(self, y_true, y_pred, sample_weight=None):
    y_true = tf.cast(y_true, tf.bool)
    y_pred = tf.cast(y_pred, tf.bool)

    values = tf.logical_and(tf.equal(y_true, True), tf.equal(y_pred, True))
    values = tf.cast(values, self.dtype)
    if sample_weight is not None:
      sample_weight = tf.cast(sample_weight, self.dtype)
      sample_weight = tf.broadcast_weights(sample_weight, values)
      values = tf.multiply(values, sample_weight)
    self.true_positives.assign_add(tf.reduce_sum(values))

  def result(self):
    return self.true_positives

__init__

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__init__(
    name=None,
    dtype=None,
    **kwargs
)

__new__

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@staticmethod
__new__(
    cls,
    *args,
    **kwargs
)

Create and return a new object. See help(type) for accurate signature.

Methods

tf.keras.metrics.Metric.add_weight

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add_weight(
    name,
    shape=(),
    aggregation=tf.VariableAggregation.SUM,
    synchronization=tf.VariableSynchronization.ON_READ,
    initializer=None,
    dtype=None
)

Adds state variable. Only for use by subclasses.

tf.keras.metrics.Metric.reset_states

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reset_states()

Resets all of the metric state variables.

This function is called between epochs/steps, when a metric is evaluated during training.

tf.keras.metrics.Metric.result

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result()

Computes and returns the metric value tensor.

Result computation is an idempotent operation that simply calculates the metric value using the state variables.

tf.keras.metrics.Metric.update_state

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update_state(
    *args,
    **kwargs
)

Accumulates statistics for the metric.

Please use tf.config.experimental_run_functions_eagerly(True) to execute this function eagerly for debugging or profiling.

Args:

  • *args: * **kwargs: A mini-batch of inputs to the Metric.