► Keras 2 API 文档 / 损失函数 / 回归损失

回归损失

`MeanSquaredError` class

tf_keras.losses.MeanSquaredError(reduction="auto", name="mean_squared_error")

Computes the mean of squares of errors between labels and predictions.

loss = mean(square(y_true - y_pred))

Standalone usage:

>>> y_true = [[0., 1.], [0., 0.]]
>>> y_pred = [[1., 1.], [1., 0.]]
>>> # Using 'auto'/'sum_over_batch_size' reduction type.
>>> mse = tf.keras.losses.MeanSquaredError()
>>> mse(y_true, y_pred).numpy()
0.5

>>> # Calling with 'sample_weight'.
>>> mse(y_true, y_pred, sample_weight=[0.7, 0.3]).numpy()
0.25

>>> # Using 'sum' reduction type.
>>> mse = tf.keras.losses.MeanSquaredError(
...     reduction=tf.keras.losses.Reduction.SUM)
>>> mse(y_true, y_pred).numpy()
1.0

>>> # Using 'none' reduction type.
>>> mse = tf.keras.losses.MeanSquaredError(
...     reduction=tf.keras.losses.Reduction.NONE)
>>> mse(y_true, y_pred).numpy()
array([0.5, 0.5], dtype=float32)

Usage with the compile() API:

model.compile(optimizer='sgd', loss=tf.keras.losses.MeanSquaredError())

[source]

`MeanAbsoluteError` class

tf_keras.losses.MeanAbsoluteError(reduction="auto", name="mean_absolute_error")

Computes the mean of absolute difference between labels and predictions.

loss = mean(abs(y_true - y_pred))

Standalone usage:

>>> y_true = [[0., 1.], [0., 0.]]
>>> y_pred = [[1., 1.], [1., 0.]]
>>> # Using 'auto'/'sum_over_batch_size' reduction type.
>>> mae = tf.keras.losses.MeanAbsoluteError()
>>> mae(y_true, y_pred).numpy()
0.5

>>> # Calling with 'sample_weight'.
>>> mae(y_true, y_pred, sample_weight=[0.7, 0.3]).numpy()
0.25

>>> # Using 'sum' reduction type.
>>> mae = tf.keras.losses.MeanAbsoluteError(
...     reduction=tf.keras.losses.Reduction.SUM)
>>> mae(y_true, y_pred).numpy()
1.0

>>> # Using 'none' reduction type.
>>> mae = tf.keras.losses.MeanAbsoluteError(
...     reduction=tf.keras.losses.Reduction.NONE)
>>> mae(y_true, y_pred).numpy()
array([0.5, 0.5], dtype=float32)

Usage with the compile() API:

model.compile(optimizer='sgd', loss=tf.keras.losses.MeanAbsoluteError())

[source]

`MeanAbsolutePercentageError` class

tf_keras.losses.MeanAbsolutePercentageError(
    reduction="auto", name="mean_absolute_percentage_error"
)

Computes the mean absolute percentage error between y_true & y_pred.

Formula:

loss = 100 * abs((y_true - y_pred) / y_true)

Note that to avoid dividing by zero, a small epsilon value is added to the denominator.

Standalone usage:

>>> y_true = [[2., 1.], [2., 3.]]
>>> y_pred = [[1., 1.], [1., 0.]]
>>> # Using 'auto'/'sum_over_batch_size' reduction type.
>>> mape = tf.keras.losses.MeanAbsolutePercentageError()
>>> mape(y_true, y_pred).numpy()
50.

>>> # Calling with 'sample_weight'.
>>> mape(y_true, y_pred, sample_weight=[0.7, 0.3]).numpy()
20.

>>> # Using 'sum' reduction type.
>>> mape = tf.keras.losses.MeanAbsolutePercentageError(
...     reduction=tf.keras.losses.Reduction.SUM)
>>> mape(y_true, y_pred).numpy()
100.

>>> # Using 'none' reduction type.
>>> mape = tf.keras.losses.MeanAbsolutePercentageError(
...     reduction=tf.keras.losses.Reduction.NONE)
>>> mape(y_true, y_pred).numpy()
array([25., 75.], dtype=float32)

Usage with the compile() API:

model.compile(optimizer='sgd',
              loss=tf.keras.losses.MeanAbsolutePercentageError())

[source]

`MeanSquaredLogarithmicError` class

tf_keras.losses.MeanSquaredLogarithmicError(
    reduction="auto", name="mean_squared_logarithmic_error"
)

Computes the mean squared logarithmic error between y_true & y_pred.

loss = square(log(y_true + 1.) - log(y_pred + 1.))

Standalone usage:

>>> y_true = [[0., 1.], [0., 0.]]
>>> y_pred = [[1., 1.], [1., 0.]]
>>> # Using 'auto'/'sum_over_batch_size' reduction type.
>>> msle = tf.keras.losses.MeanSquaredLogarithmicError()
>>> msle(y_true, y_pred).numpy()
0.240

>>> # Calling with 'sample_weight'.
>>> msle(y_true, y_pred, sample_weight=[0.7, 0.3]).numpy()
0.120

>>> # Using 'sum' reduction type.
>>> msle = tf.keras.losses.MeanSquaredLogarithmicError(
...     reduction=tf.keras.losses.Reduction.SUM)
>>> msle(y_true, y_pred).numpy()
0.480

>>> # Using 'none' reduction type.
>>> msle = tf.keras.losses.MeanSquaredLogarithmicError(
...     reduction=tf.keras.losses.Reduction.NONE)
>>> msle(y_true, y_pred).numpy()
array([0.240, 0.240], dtype=float32)

Usage with the compile() API:

model.compile(optimizer='sgd',
              loss=tf.keras.losses.MeanSquaredLogarithmicError())

[source]

`CosineSimilarity` class

tf_keras.losses.CosineSimilarity(axis=-1, reduction="auto", name="cosine_similarity")

Computes the cosine similarity between labels and predictions.

Note that it is a number between -1 and 1. When it is a negative number between -1 and 0, 0 indicates orthogonality and values closer to -1 indicate greater similarity. The values closer to 1 indicate greater dissimilarity. This makes it usable as a loss function in a setting where you try to maximize the proximity between predictions and targets. If either y_true or y_pred is a zero vector, cosine similarity will be 0 regardless of the proximity between predictions and targets.

loss = -sum(l2_norm(y_true) * l2_norm(y_pred))

Standalone usage:

>>> y_true = [[0., 1.], [1., 1.]]
>>> y_pred = [[1., 0.], [1., 1.]]
>>> # Using 'auto'/'sum_over_batch_size' reduction type.
>>> cosine_loss = tf.keras.losses.CosineSimilarity(axis=1)
>>> # l2_norm(y_true) = [[0., 1.], [1./1.414, 1./1.414]]
>>> # l2_norm(y_pred) = [[1., 0.], [1./1.414, 1./1.414]]
>>> # l2_norm(y_true) . l2_norm(y_pred) = [[0., 0.], [0.5, 0.5]]
>>> # loss = mean(sum(l2_norm(y_true) . l2_norm(y_pred), axis=1))
>>> #       = -((0. + 0.) +  (0.5 + 0.5)) / 2
>>> cosine_loss(y_true, y_pred).numpy()
-0.5

>>> # Calling with 'sample_weight'.
>>> cosine_loss(y_true, y_pred, sample_weight=[0.8, 0.2]).numpy()
-0.0999

>>> # Using 'sum' reduction type.
>>> cosine_loss = tf.keras.losses.CosineSimilarity(axis=1,
...     reduction=tf.keras.losses.Reduction.SUM)
>>> cosine_loss(y_true, y_pred).numpy()
-0.999

>>> # Using 'none' reduction type.
>>> cosine_loss = tf.keras.losses.CosineSimilarity(axis=1,
...     reduction=tf.keras.losses.Reduction.NONE)
>>> cosine_loss(y_true, y_pred).numpy()
array([-0., -0.999], dtype=float32)

Usage with the compile() API:

model.compile(optimizer='sgd',
              loss=tf.keras.losses.CosineSimilarity(axis=1))

Arguments

axis: The axis along which the cosine similarity is computed (the features axis). Defaults to -1.
reduction: Type of tf.keras.losses.Reduction to apply to loss. Default value is AUTO. AUTO indicates that the reduction option will be determined by the usage context. For almost all cases this defaults to SUM_OVER_BATCH_SIZE. When used under a tf.distribute.Strategy, except via Model.compile() and Model.fit(), using AUTO or SUM_OVER_BATCH_SIZE will raise an error. Please see this custom training tutorial for more details.
name: Optional name for the instance. Defaults to 'cosine_similarity'.

[source]

`mean_squared_error` function

tf_keras.losses.mean_squared_error(y_true, y_pred)

Computes the mean squared error between labels and predictions.

After computing the squared distance between the inputs, the mean value over the last dimension is returned.

loss = mean(square(y_true - y_pred), axis=-1)

Standalone usage:

>>> y_true = np.random.randint(0, 2, size=(2, 3))
>>> y_pred = np.random.random(size=(2, 3))
>>> loss = tf.keras.losses.mean_squared_error(y_true, y_pred)
>>> assert loss.shape == (2,)
>>> assert np.array_equal(
...     loss.numpy(), np.mean(np.square(y_true - y_pred), axis=-1))

Arguments

y_true: Ground truth values. shape = [batch_size, d0, .. dN].
y_pred: The predicted values. shape = [batch_size, d0, .. dN].

Returns

Mean squared error values. shape = [batch_size, d0, .. dN-1].

[source]

`mean_absolute_error` function

tf_keras.losses.mean_absolute_error(y_true, y_pred)

Computes the mean absolute error between labels and predictions.

loss = mean(abs(y_true - y_pred), axis=-1)

Standalone usage:

>>> y_true = np.random.randint(0, 2, size=(2, 3))
>>> y_pred = np.random.random(size=(2, 3))
>>> loss = tf.keras.losses.mean_absolute_error(y_true, y_pred)
>>> assert loss.shape == (2,)
>>> assert np.array_equal(
...     loss.numpy(), np.mean(np.abs(y_true - y_pred), axis=-1))

Arguments

y_true: Ground truth values. shape = [batch_size, d0, .. dN].
y_pred: The predicted values. shape = [batch_size, d0, .. dN].

Returns

Mean absolute error values. shape = [batch_size, d0, .. dN-1].

[source]

`mean_absolute_percentage_error` function

tf_keras.losses.mean_absolute_percentage_error(y_true, y_pred)

Computes the mean absolute percentage error between y_true & y_pred.

loss = 100 * mean(abs((y_true - y_pred) / y_true), axis=-1)

Standalone usage:

>>> y_true = np.random.random(size=(2, 3))
>>> y_true = np.maximum(y_true, 1e-7)  # Prevent division by zero
>>> y_pred = np.random.random(size=(2, 3))
>>> loss = tf.keras.losses.mean_absolute_percentage_error(y_true, y_pred)
>>> assert loss.shape == (2,)
>>> assert np.array_equal(
...     loss.numpy(),
...     100. * np.mean(np.abs((y_true - y_pred) / y_true), axis=-1))

Arguments

y_true: Ground truth values. shape = [batch_size, d0, .. dN].
y_pred: The predicted values. shape = [batch_size, d0, .. dN].

Returns

Mean absolute percentage error values. shape = [batch_size, d0, .. dN-1].

[source]

`mean_squared_logarithmic_error` function

tf_keras.losses.mean_squared_logarithmic_error(y_true, y_pred)

Computes the mean squared logarithmic error between y_true & y_pred.

loss = mean(square(log(y_true + 1) - log(y_pred + 1)), axis=-1)

Standalone usage:

>>> y_true = np.random.randint(0, 2, size=(2, 3))
>>> y_pred = np.random.random(size=(2, 3))
>>> loss = tf.keras.losses.mean_squared_logarithmic_error(y_true, y_pred)
>>> assert loss.shape == (2,)
>>> y_true = np.maximum(y_true, 1e-7)
>>> y_pred = np.maximum(y_pred, 1e-7)
>>> assert np.allclose(
...     loss.numpy(),
...     np.mean(
...         np.square(np.log(y_true + 1.) - np.log(y_pred + 1.)), axis=-1))

Arguments

y_true: Ground truth values. shape = [batch_size, d0, .. dN].
y_pred: The predicted values. shape = [batch_size, d0, .. dN].

Returns

Mean squared logarithmic error values. shape = [batch_size, d0, .. dN-1].

[source]

`cosine_similarity` function

tf_keras.losses.cosine_similarity(y_true, y_pred, axis=-1)

Computes the cosine similarity between labels and predictions.

loss = -sum(l2_norm(y_true) * l2_norm(y_pred))

Standalone usage:

>>> y_true = [[0., 1.], [1., 1.], [1., 1.]]
>>> y_pred = [[1., 0.], [1., 1.], [-1., -1.]]
>>> loss = tf.keras.losses.cosine_similarity(y_true, y_pred, axis=1)
>>> loss.numpy()
array([-0., -0.999, 0.999], dtype=float32)

Arguments

y_true: Tensor of true targets.
y_pred: Tensor of predicted targets.
axis: Axis along which to determine similarity.

Returns

Cosine similarity tensor.

[source]

`Huber` class

tf_keras.losses.Huber(delta=1.0, reduction="auto", name="huber_loss")

Computes the Huber loss between y_true & y_pred.

For each value x in error = y_true - y_pred:

loss = 0.5 * x^2                  if |x| <= d
loss = 0.5 * d^2 + d * (|x| - d)  if |x| > d

where d is delta. See: https://en.wikipedia.org/wiki/Huber_loss

Standalone usage:

>>> y_true = [[0, 1], [0, 0]]
>>> y_pred = [[0.6, 0.4], [0.4, 0.6]]
>>> # Using 'auto'/'sum_over_batch_size' reduction type.
>>> h = tf.keras.losses.Huber()
>>> h(y_true, y_pred).numpy()
0.155

>>> # Calling with 'sample_weight'.
>>> h(y_true, y_pred, sample_weight=[1, 0]).numpy()
0.09

>>> # Using 'sum' reduction type.
>>> h = tf.keras.losses.Huber(
...     reduction=tf.keras.losses.Reduction.SUM)
>>> h(y_true, y_pred).numpy()
0.31

>>> # Using 'none' reduction type.
>>> h = tf.keras.losses.Huber(
...     reduction=tf.keras.losses.Reduction.NONE)
>>> h(y_true, y_pred).numpy()
array([0.18, 0.13], dtype=float32)

Usage with the compile() API:

model.compile(optimizer='sgd', loss=tf.keras.losses.Huber())

[source]

`huber` function

tf_keras.losses.huber(y_true, y_pred, delta=1.0)

Computes Huber loss value.

For each value x in error = y_true - y_pred:

loss = 0.5 * x^2                  if |x| <= d
loss = d * |x| - 0.5 * d^2        if |x| > d

where d is delta. See: https://en.wikipedia.org/wiki/Huber_loss

Arguments

y_true: tensor of true targets.
y_pred: tensor of predicted targets.
delta: A float, the point where the Huber loss function changes from a quadratic to linear.

Returns

Tensor with one scalar loss entry per sample.

[source]

`LogCosh` class

tf_keras.losses.LogCosh(reduction="auto", name="log_cosh")

Computes the logarithm of the hyperbolic cosine of the prediction error.

logcosh = log((exp(x) + exp(-x))/2), where x is the error y_pred - y_true.

Standalone usage:

>>> y_true = [[0., 1.], [0., 0.]]
>>> y_pred = [[1., 1.], [0., 0.]]
>>> # Using 'auto'/'sum_over_batch_size' reduction type.
>>> l = tf.keras.losses.LogCosh()
>>> l(y_true, y_pred).numpy()
0.108

>>> # Calling with 'sample_weight'.
>>> l(y_true, y_pred, sample_weight=[0.8, 0.2]).numpy()
0.087

>>> # Using 'sum' reduction type.
>>> l = tf.keras.losses.LogCosh(
...     reduction=tf.keras.losses.Reduction.SUM)
>>> l(y_true, y_pred).numpy()
0.217

>>> # Using 'none' reduction type.
>>> l = tf.keras.losses.LogCosh(
...     reduction=tf.keras.losses.Reduction.NONE)
>>> l(y_true, y_pred).numpy()
array([0.217, 0.], dtype=float32)

Usage with the compile() API:

model.compile(optimizer='sgd', loss=tf.keras.losses.LogCosh())

[source]

`log_cosh` function

tf_keras.losses.log_cosh(y_true, y_pred)

Logarithm of the hyperbolic cosine of the prediction error.

log(cosh(x)) is approximately equal to (x ** 2) / 2 for small x and to abs(x) - log(2) for large x. This means that 'logcosh' works mostly like the mean squared error, but will not be so strongly affected by the occasional wildly incorrect prediction.

Standalone usage:

>>> y_true = np.random.random(size=(2, 3))
>>> y_pred = np.random.random(size=(2, 3))
>>> loss = tf.keras.losses.logcosh(y_true, y_pred)
>>> assert loss.shape == (2,)
>>> x = y_pred - y_true
>>> assert np.allclose(
...     loss.numpy(),
...     np.mean(x + np.log(np.exp(-2. * x) + 1.) - tf.math.log(2.),
...             axis=-1),
...     atol=1e-5)

Arguments

y_true: Ground truth values. shape = [batch_size, d0, .. dN].
y_pred: The predicted values. shape = [batch_size, d0, .. dN].

Returns

Logcosh error values. shape = [batch_size, d0, .. dN-1].

回归损失

MeanSquaredError class

MeanAbsoluteError class

MeanAbsolutePercentageError class

MeanSquaredLogarithmicError class

CosineSimilarity class

mean_squared_error function

mean_absolute_error function

mean_absolute_percentage_error function

mean_squared_logarithmic_error function

cosine_similarity function

Huber class

huber function

LogCosh class

log_cosh function

回归损失

MeanSquaredError class

MeanAbsoluteError class

MeanAbsolutePercentageError class

MeanSquaredLogarithmicError class

CosineSimilarity class

mean_squared_error function

mean_absolute_error function

mean_absolute_percentage_error function

mean_squared_logarithmic_error function

cosine_similarity function

Huber class

huber function

LogCosh class

log_cosh function

`MeanSquaredError` class

`MeanAbsoluteError` class

`MeanAbsolutePercentageError` class

`MeanSquaredLogarithmicError` class

`CosineSimilarity` class

`mean_squared_error` function

`mean_absolute_error` function

`mean_absolute_percentage_error` function

`mean_squared_logarithmic_error` function

`cosine_similarity` function

`Huber` class

`huber` function

`LogCosh` class

`log_cosh` function