[source]

Dense

keras.layers.core.Dense(output_dim, init='glorot_uniform', activation=None, weights=None, W_regularizer=None, b_regularizer=None, activity_regularizer=None, W_constraint=None, b_constraint=None, bias=True, input_dim=None)

Just your regular densely-connected NN layer.

Example

# as first layer in a sequential model:
model = Sequential()
model.add(Dense(32, input_dim=16))
# now the model will take as input arrays of shape (*, 16)
# and output arrays of shape (*, 32)

# this is equivalent to the above:
model = Sequential()
model.add(Dense(32, input_shape=(16,)))

# after the first layer, you don't need to specify
# the size of the input anymore:
model.add(Dense(32))

Arguments

  • output_dim: int > 0.
  • init: name of initialization function for the weights of the layer (see initializations), or alternatively, Theano function to use for weights initialization. This parameter is only relevant if you don't pass a weights argument.
  • activation: name of activation function to use (see activations), or alternatively, elementwise Theano function. If you don't specify anything, no activation is applied (ie. "linear" activation: a(x) = x).
  • weights: list of Numpy arrays to set as initial weights. The list should have 2 elements, of shape (input_dim, output_dim) and (output_dim,) for weights and biases respectively.
  • W_regularizer: instance of WeightRegularizer (eg. L1 or L2 regularization), applied to the main weights matrix.
  • b_regularizer: instance of WeightRegularizer, applied to the bias.
  • activity_regularizer: instance of ActivityRegularizer, applied to the network output.
  • W_constraint: instance of the constraints module (eg. maxnorm, nonneg), applied to the main weights matrix.
  • b_constraint: instance of the constraints module, applied to the bias.
  • bias: whether to include a bias (i.e. make the layer affine rather than linear).
  • input_dim: dimensionality of the input (integer). This argument (or alternatively, the keyword argument input_shape) is required when using this layer as the first layer in a model.

Input shape

nD tensor with shape: (nb_samples, ..., input_dim). The most common situation would be a 2D input with shape (nb_samples, input_dim).

Output shape

nD tensor with shape: (nb_samples, ..., output_dim). For instance, for a 2D input with shape (nb_samples, input_dim), the output would have shape (nb_samples, output_dim).

[source]

Activation

keras.layers.core.Activation(activation)

Applies an activation function to an output.

Arguments

  • activation: name of activation function to use
    • (see: activations), or alternatively, a Theano or TensorFlow operation.

Input shape

Arbitrary. Use the keyword argument input_shape (tuple of integers, does not include the samples axis) when using this layer as the first layer in a model.

Output shape

Same shape as input.

[source]

Dropout

keras.layers.core.Dropout(p, noise_shape=None, seed=None)

Applies Dropout to the input.

Dropout consists in randomly setting a fraction p of input units to 0 at each update during training time, which helps prevent overfitting.

Arguments

  • p: float between 0 and 1. Fraction of the input units to drop.
  • noise_shape: 1D integer tensor representing the shape of the binary dropout mask that will be multiplied with the input. For instance, if your inputs ahve shape (batch_size, timesteps, features) and you want the dropout mask to be the same for all timesteps, you can use noise_shape=(batch_size, 1, features).
  • seed: A Python integer to use as random seed.

References

[source]

Flatten

keras.layers.core.Flatten()

Flattens the input. Does not affect the batch size.

Example

model = Sequential()
model.add(Convolution2D(64, 3, 3,
            border_mode='same',
            input_shape=(3, 32, 32)))
# now: model.output_shape == (None, 64, 32, 32)

model.add(Flatten())
# now: model.output_shape == (None, 65536)

[source]

Reshape

keras.layers.core.Reshape(target_shape)

Reshapes an output to a certain shape.

Arguments

  • target_shape: target shape. Tuple of integers, does not include the samples dimension (batch size).

Input shape

Arbitrary, although all dimensions in the input shaped must be fixed. Use the keyword argument input_shape (tuple of integers, does not include the samples axis) when using this layer as the first layer in a model.

Output shape

(batch_size,) + target_shape

Example

# as first layer in a Sequential model
model = Sequential()
model.add(Reshape((3, 4), input_shape=(12,)))
# now: model.output_shape == (None, 3, 4)
# note: `None` is the batch dimension

# as intermediate layer in a Sequential model
model.add(Reshape((6, 2)))
# now: model.output_shape == (None, 6, 2)

# also supports shape inference using `-1` as dimension
model.add(Reshape((-1, 2, 2)))
# now: model.output_shape == (None, 3, 2, 2)

[source]

Permute

keras.layers.core.Permute(dims)

Permutes the dimensions of the input according to a given pattern.

Useful for e.g. connecting RNNs and convnets together.

Example

model = Sequential()
model.add(Permute((2, 1), input_shape=(10, 64)))
# now: model.output_shape == (None, 64, 10)
# note: `None` is the batch dimension

Arguments

  • dims: Tuple of integers. Permutation pattern, does not include the samples dimension. Indexing starts at 1. For instance, (2, 1) permutes the first and second dimension of the input.

Input shape

Arbitrary. Use the keyword argument input_shape (tuple of integers, does not include the samples axis) when using this layer as the first layer in a model.

Output shape

Same as the input shape, but with the dimensions re-ordered according to the specified pattern.

[source]

RepeatVector

keras.layers.core.RepeatVector(n)

Repeats the input n times.

Example

model = Sequential()
model.add(Dense(32, input_dim=32))
# now: model.output_shape == (None, 32)
# note: `None` is the batch dimension

model.add(RepeatVector(3))
# now: model.output_shape == (None, 3, 32)

Arguments

  • n: integer, repetition factor.

Input shape

2D tensor of shape (nb_samples, features).

Output shape

3D tensor of shape (nb_samples, n, features).

[source]

Merge

keras.engine.topology.Merge(layers=None, mode='sum', concat_axis=-1, dot_axes=-1, output_shape=None, output_mask=None, arguments=None, node_indices=None, tensor_indices=None, name=None)

A Merge layer can be used to merge a list of tensors into a single tensor, following some merge mode.

Example

model1 = Sequential()
model1.add(Dense(32, input_dim=32))

model2 = Sequential()
model2.add(Dense(32, input_dim=32))

merged_model = Sequential()
merged_model.add(Merge([model1, model2], mode='concat', concat_axis=1))

Arguments

  • layers: Can be a list of Keras tensors or a list of layer instances. Must be more than one layer/tensor.
  • mode: String or lambda/function. If string, must be one
    • of: 'sum', 'mul', 'concat', 'ave', 'cos', 'dot', 'max'. If lambda/function, it should take as input a list of tensors and return a single tensor.
  • concat_axis: Integer, axis to use in mode concat.
  • dot_axes: Integer or tuple of integers, axes to use in mode dot or cos.
  • output_shape: Either a shape tuple (tuple of integers), or a lambda/function to compute output_shape (only if merge mode is a lambda/function). If the argument is a tuple, it should be expected output shape, not including the batch size (same convention as the input_shape argument in layers). If the argument is callable, it should take as input a list of shape tuples
    • (1:1 mapping to input tensors) and return a single shape tuple, including the batch size (same convention as the get_output_shape_for method of layers).
  • node_indices: Optional list of integers containing the output node index for each input layer (in case some input layers have multiple output nodes). will default to an array of 0s if not provided.
  • tensor_indices: Optional list of indices of output tensors to consider for merging (in case some input layer node returns multiple tensors).
  • output_mask: Mask or lambda/function to compute the output mask (only if merge mode is a lambda/function). If the latter case, it should take as input a list of masks and return a single mask.

[source]

Lambda

keras.layers.core.Lambda(function, output_shape=None, arguments=None)

Used for evaluating an arbitrary expressions on an input.

Examples

# add a x -> x^2 layer
model.add(Lambda(lambda x: x ** 2))

# add a layer that returns the concatenation
# of the positive part of the input and
# the opposite of the negative part

def antirectifier(x):
    x -= K.mean(x, axis=1, keepdims=True)
    x = K.l2_normalize(x, axis=1)
    pos = K.relu(x)
    neg = K.relu(-x)
    return K.concatenate([pos, neg], axis=1)

def antirectifier_output_shape(input_shape):
    shape = list(input_shape)
    assert len(shape) == 2  # only valid for 2D tensors
    shape[-1] *= 2
    return tuple(shape)

model.add(Lambda(antirectifier,
         output_shape=antirectifier_output_shape))

Arguments

  • function: The function to be evaluated. Takes input tensor as first argument.
  • output_shape: Expected output shape from function. Can be a tuple or function. If a tuple, it only specifies the first dimension onward; sample dimension is assumed either the same as the input: output_shape = (input_shape[0], ) + output_shape or, the input is None and the sample dimension is also None: output_shape = (None, ) + output_shape If a function, it specifies the entire shape as a function of the input shape: output_shape = f(input_shape)
  • arguments: optional dictionary of keyword arguments to be passed to the function.

Input shape

Arbitrary. Use the keyword argument input_shape (tuple of integers, does not include the samples axis) when using this layer as the first layer in a model.

Output shape

Specified by output_shape argument.

[source]

ActivityRegularization

keras.layers.core.ActivityRegularization(l1=0.0, l2=0.0)

Layer that applies an update to the cost function based input activity.

Arguments

  • l1: L1 regularization factor (positive float).
  • l2: L2 regularization factor (positive float).

Input shape

Arbitrary. Use the keyword argument input_shape (tuple of integers, does not include the samples axis) when using this layer as the first layer in a model.

Output shape

Same shape as input.

[source]

Masking

keras.layers.core.Masking(mask_value=0.0)

Masks a sequence by using a mask value to skip timesteps.

For each timestep in the input tensor (dimension #1 in the tensor), if all values in the input tensor at that timestep are equal to mask_value, then the timestep will masked (skipped) in all downstream layers (as long as they support masking).

If any downstream layer does not support masking yet receives such an input mask, an exception will be raised.

Example

Consider a Numpy data array x of shape (samples, timesteps, features), to be fed to a LSTM layer. You want to mask timestep #3 and #5 because you lack data for these timesteps. You can:

  • set x[:, 3, :] = 0. and x[:, 5, :] = 0.
  • insert a Masking layer with mask_value=0. before the LSTM layer:
model = Sequential()
model.add(Masking(mask_value=0., input_shape=(timesteps, features)))
model.add(LSTM(32))

[source]

Highway

keras.layers.core.Highway(init='glorot_uniform', activation=None, weights=None, W_regularizer=None, b_regularizer=None, activity_regularizer=None, W_constraint=None, b_constraint=None, bias=True, input_dim=None)

Densely connected highway network.

Highway layers are a natural extension of LSTMs to feedforward networks.

Arguments

  • init: name of initialization function for the weights of the layer (see initializations), or alternatively, Theano function to use for weights initialization. This parameter is only relevant if you don't pass a weights argument.
  • activation: name of activation function to use (see activations), or alternatively, elementwise Theano function. If you don't specify anything, no activation is applied (ie. "linear" activation: a(x) = x).
  • weights: list of Numpy arrays to set as initial weights. The list should have 2 elements, of shape (input_dim, output_dim) and (output_dim,) for weights and biases respectively.
  • W_regularizer: instance of WeightRegularizer (eg. L1 or L2 regularization), applied to the main weights matrix.
  • b_regularizer: instance of WeightRegularizer, applied to the bias.
  • activity_regularizer: instance of ActivityRegularizer, applied to the network output.
  • W_constraint: instance of the constraints module (eg. maxnorm, nonneg), applied to the main weights matrix.
  • b_constraint: instance of the constraints module, applied to the bias.
  • bias: whether to include a bias (i.e. make the layer affine rather than linear).
  • input_dim: dimensionality of the input (integer). This argument (or alternatively, the keyword argument input_shape) is required when using this layer as the first layer in a model.

Input shape

2D tensor with shape: (nb_samples, input_dim).

Output shape

2D tensor with shape: (nb_samples, input_dim).

References

[source]

MaxoutDense

keras.layers.core.MaxoutDense(output_dim, nb_feature=4, init='glorot_uniform', weights=None, W_regularizer=None, b_regularizer=None, activity_regularizer=None, W_constraint=None, b_constraint=None, bias=True, input_dim=None)

A dense maxout layer.

A MaxoutDense layer takes the element-wise maximum of nb_feature Dense(input_dim, output_dim) linear layers. This allows the layer to learn a convex, piecewise linear activation function over the inputs.

Note that this is a linear layer; if you wish to apply activation function (you shouldn't need to --they are universal function approximators), an Activation layer must be added after.

Arguments

  • output_dim: int > 0.
  • nb_feature: number of Dense layers to use internally.
  • init: name of initialization function for the weights of the layer (see initializations), or alternatively, Theano function to use for weights initialization. This parameter is only relevant if you don't pass a weights argument.
  • weights: list of Numpy arrays to set as initial weights. The list should have 2 elements, of shape (input_dim, output_dim) and (output_dim,) for weights and biases respectively.
  • W_regularizer: instance of WeightRegularizer (eg. L1 or L2 regularization), applied to the main weights matrix.
  • b_regularizer: instance of WeightRegularizer, applied to the bias.
  • activity_regularizer: instance of ActivityRegularizer, applied to the network output.
  • W_constraint: instance of the constraints module (eg. maxnorm, nonneg), applied to the main weights matrix.
  • b_constraint: instance of the constraints module, applied to the bias.
  • bias: whether to include a bias (i.e. make the layer affine rather than linear).
  • input_dim: dimensionality of the input (integer). This argument (or alternatively, the keyword argument input_shape) is required when using this layer as the first layer in a model.

Input shape

2D tensor with shape: (nb_samples, input_dim).

Output shape

2D tensor with shape: (nb_samples, output_dim).

References