losses

Custom Keras losses, used by the AshPy executors.

Classes

DHingeLoss	Discriminator Hinge Loss as Keras Metric.
DLeastSquare	Discriminator Least Square Loss as tf.keras.losses.Loss.
DMinMax	Implementation of MinMax Discriminator loss as tf.keras.losses.Loss.
GHingeLoss	Generator Hinge Loss as Keras Metric.
L1	L1 Loss implementation as tf.keras.losses.Loss.

class ashpy.keras.losses.DHingeLoss

Bases: tensorflow.python.keras.losses.Loss

Discriminator Hinge Loss as Keras Metric.

See Geometric GAN [1]_ for more details.

The Discriminator Hinge loss is the hinge version of the adversarial loss. The Hinge loss is defined as:

\[L_{\text{hinge}} = \max(0, 1 -t y)\]

where y is the Discriminator output and t is the target class (+1 or -1 in the case of binary classification).

For the case of GANs:

\[L_{D_{\text{hinge}}} = - \mathbb{E}_{(x,y) \sim p_data} [ \min(0, -1+D(x,y)) ] - \mathbb{E}_{x \sim p_x, y \sim p_data} [ \min(0, -1 - D(G(z),y)) ]\]

[1]	Geometric GAN https://arxiv.org/abs/1705.02894

__init__()

Initialize the Loss.

Return type:None

call(d_real, d_fake)

Compute the hinge loss.

Return type:Tensor

reduction

Return the current reduction for this type of loss.

Return type:ReductionV2

class ashpy.keras.losses.DLeastSquare

Bases: tensorflow.python.keras.losses.Loss

Discriminator Least Square Loss as tf.keras.losses.Loss.

__init__()

Least square Loss for Discriminator.

Reference: Least Squares Generative Adversarial Networks [1]_ .

Basically the Mean Squared Error between the discriminator output when evaluated in fake samples and 0 and the discriminator output when evaluated in real samples and 1: For the unconditioned case this is:

\[L_{D} = \frac{1}{2} E[(D(x) - 1)^2 + (0 - D(G(z))^2]\]

where x are real samples and z is the latent vector.

For the conditioned case this is:

\[L_{D} = \frac{1}{2} E[(D(x, c) - 1)^2 + (0 - D(G(c), c)^2]\]

where c is the condition and x are real samples.

[1]	Least Squares Generative Adversarial Networks https://arxiv.org/abs/1611.04076

Return type:None

call(d_real, d_fake)

Compute the Least Square Loss.

Parameters:

• d_real (tf.Tensor) – Discriminator evaluated in real samples.
• d_fake (tf.Tensor) – Discriminator evaluated in fake samples.

Return type:

Tensor

Returns:

tf.Tensor – Loss.

reduction

Return the reduction type for this loss.

Return type:ReductionV2 Returns:tf.keras.losses.Reduction – Reduction.

class ashpy.keras.losses.DMinMax(from_logits=True, label_smoothing=0.0)

Bases: tensorflow.python.keras.losses.Loss

Implementation of MinMax Discriminator loss as tf.keras.losses.Loss.

\[L_{D} = - \frac{1}{2} E [\log(D(x)) + \log (1 - D(G(z))]\]

__init__(from_logits=True, label_smoothing=0.0)

Initialize the loss.

Return type:None

call(d_real, d_fake)

Compute the MinMax Loss.

Play the DiscriminatorMinMax game between the discriminator computed in real and the discriminator compute with fake inputs.

Parameters:

• d_real (tf.Tensor) – Real data.
• d_fake (tf.Tensor) – Fake (generated) data.

Return type:

Tensor

Returns:

tf.Tensor – Output Tensor.

reduction

Return the reduction type of this loss.

Return type:ReductionV2 Returns::py:classes:`tf.keras.losses.Reduction` – Reduction.

class ashpy.keras.losses.GHingeLoss

Bases: tensorflow.python.keras.losses.Loss

Generator Hinge Loss as Keras Metric.

See Geometric GAN [1]_ for more details. The Generator Hinge loss is the hinge version of the adversarial loss. The Hinge loss is defined as:

\[L_{\text{hinge}} = \max(0, 1 - t y)\]

where y is the Discriminator output and t is the target class (+1 or -1 in the case of binary classification). The target class of the generated images is +1.

For the case of GANs

\[L_{G_{\text{hinge}}} = - \mathbb{E}_{(x \sim p_x, y \sim p_data} [ \min(0, -1+D(G(x),y)) ]\]

This can be simply approximated as:

\[L_{G_{\text{hinge}}} = - \mathbb{E}_{(x \sim p_x, y \sim p_data} [ D(G(x),y) ]\]

[1]	Geometric GAN https://arxiv.org/abs/1705.02894

__init__()

Initialize the Loss.

Return type:None

call(d_real, d_fake)

Compute the hinge loss.

Return type:Tensor

reduction

Return the current reduction for this type of loss.

Return type:ReductionV2

class ashpy.keras.losses.L1

Bases: tensorflow.python.keras.losses.Loss

L1 Loss implementation as tf.keras.losses.Loss.

__init__()

Initialize the Loss.

Return type:None

call(x, y)

Compute the mean of the l1 between x and y.

Return type:Tensor

reduction

Return the current reduction for this type of loss.

Return type:ReductionV2