What are layers?

Each layer in a neural network configuration represents a unit of hidden units. When layers are stacked together, they represent a deep neural network.

Using layers

All layers available in Eclipse Deeplearning4j can be used either in a MultiLayerNetwork or ComputationGraph. When configuring a neural network, you pass the layer configuration and the network will instantiate the layer for you.

Layers vs. vertices

If you are configuring complex networks such as InceptionV4, you will need to use the ComputationGraph API and join different branches together using vertices. Check the vertices for more information.

General layers

ActivationLayer

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Activation layer is a simple layer that applies the specified activation function to the input activations

clone

public ActivationLayer clone() 

• param activation Activation function for the layer

activation

public Builder activation(String activationFunction) 

Activation function for the layer

activation

public Builder activation(IActivation activationFunction) 

• param activationFunction Activation function for the layer

activation

public Builder activation(Activation activation) 

• param activation Activation function for the layer

DenseLayer

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Dense layer: a standard fully connected feed forward layer

hasBias

public Builder hasBias(boolean hasBias) 

If true (default): include bias parameters in the model. False: no bias.

hasLayerNorm

public Builder hasLayerNorm(boolean hasLayerNorm)

If true (default = false): enable layer normalization on this layer

DropoutLayer

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Dropout layer. This layer simply applies dropout at training time, and passes activations through unmodified at test

build

public DropoutLayer build() 

Create a dropout layer with standard {- link Dropout}, with the specified probability of retaining the inputactivation. See {- link Dropout} for the full details

• param dropout Activation retain probability.

EmbeddingLayer

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Embedding layer: feed-forward layer that expects single integers per example as input (class numbers, in range 0 tothe equivalent one-hot representation. Mathematically, EmbeddingLayer is equivalent to using a DenseLayer with aone-hot representation for the input; however, it can be much more efficient with a large number of classes (as adense layer + one-hot input does a matrix multiply with all but one value being zero).Note: can only be used as the first layer for a networkNote 2: For a given example index i, the output is activationFunction(weights.getRow(i) + bias), hence theweight rows can be considered a vector/embedding for each example. Note also that embedding layer has anactivation function (set to IDENTITY to disable) and optional bias (which is disabled by default)

hasBias

public Builder hasBias(boolean hasBias) 

If true: include bias parameters in the layer. False (default): no bias.

weightInit

public Builder weightInit(EmbeddingInitializer embeddingInitializer)

Initialize the embedding layer using the specified EmbeddingInitializer - such as a Word2Vec instance

• param embeddingInitializer Source of the embedding layer weights

weightInit

public Builder weightInit(INDArray vectors)

Initialize the embedding layer using values from the specified array. Note that the array should have shape[vocabSize, vectorSize]. After copying values from the array to initialize the network parameters, the inputarray will be discarded (so that, if necessary, it can be garbage collected)

• param vectors Vectors to initialize the embedding layer with

EmbeddingSequenceLayer

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Embedding layer for sequences: feed-forward layer that expects fixed-length number (inputLength) of integers/indicesper example as input, ranged from 0 to numClasses - 1. This input thus has shape [numExamples, inputLength] or shape[numExamples, 1, inputLength]. The output of this layer is 3D (sequence/time series), namely of shape[numExamples, nOut, inputLength].Note: can only be used as the first layer for a networkNote 2: For a given example index i, the output is activationFunction(weights.getRow(i) + bias), hence theweight rows can be considered a vector/embedding of each index. Note also that embedding layer has an activationfunction (set to IDENTITY to disable) and optional bias (which is disabled by default)

hasBias

public Builder hasBias(boolean hasBias) 

If true: include bias parameters in the layer. False (default): no bias.

inputLength

public Builder inputLength(int inputLength) 

Set input sequence length for this embedding layer.

• param inputLength input sequence length
• return Builder

inferInputLength

public Builder inferInputLength(boolean inferInputLength) 

Set input sequence inference mode for embedding layer.

• param inferInputLength whether to infer input length
• return Builder

weightInit

public Builder weightInit(EmbeddingInitializer embeddingInitializer)

Initialize the embedding layer using the specified EmbeddingInitializer - such as a Word2Vec instance

• param embeddingInitializer Source of the embedding layer weights

weightInit

public Builder weightInit(INDArray vectors)

Initialize the embedding layer using values from the specified array. Note that the array should have shape[vocabSize, vectorSize]. After copying values from the array to initialize the network parameters, the inputarray will be discarded (so that, if necessary, it can be garbage collected)

• param vectors Vectors to initialize the embedding layer with

GlobalPoolingLayer

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Global pooling layer - used to do pooling over time for RNNs, and 2d pooling for CNNs. Supports the following

Global pooling layer can also handle mask arrays when dealing with variable length inputs. Mask arrays are assumed tobe 2d, and are fed forward through the network during training or post-training forward pass: - Time series: maskarrays are shape [miniBatchSize, maxTimeSeriesLength] and contain values 0 or 1 only - CNNs: mask have shape[miniBatchSize, height] or [miniBatchSize, width]. Important: the current implementation assumes that for CNNs +variable length (masking), the input shape is [miniBatchSize, channels, height, 1] or [miniBatchSize, channels, 1,width] respectively. This is the case with global pooling in architectures like CNN for sentence classification.

Behaviour with default settings: - 3d (time series) input with shape [miniBatchSize, vectorSize,timeSeriesLength] -> 2d output [miniBatchSize, vectorSize] - 4d (CNN) input with shape [miniBatchSize, channels,height, width] -> 2d output [miniBatchSize, channels] - 5d (CNN3D) input with shape [miniBatchSize, channels,depth, height, width] -> 2d output [miniBatchSize, channels]

Alternatively, by setting collapseDimensions = false in the configuration, it is possible to retain the reduceddimensions as 1s: this gives - [miniBatchSize, vectorSize, 1] for RNN output, - [miniBatchSize, channels, 1,1] for CNN output, and - [miniBatchSize, channels, 1, 1, 1] for CNN3D output.

poolingDimensions

public Builder poolingDimensions(int... poolingDimensions) 

Pooling type for global pooling

poolingType

public Builder poolingType(PoolingType poolingType) 

• param poolingType Pooling type for global pooling

collapseDimensions

public Builder collapseDimensions(boolean collapseDimensions) 

Whether to collapse dimensions when pooling or not. Usually you do want to do this. Default: true. Iftrue: - 3d (time series) input with shape [miniBatchSize, vectorSize, timeSeriesLength] -> 2d output[miniBatchSize, vectorSize] - 4d (CNN) input with shape [miniBatchSize, channels, height, width] -> 2doutput [miniBatchSize, channels] - 5d (CNN3D) input with shape [miniBatchSize, channels, depth, height,width] -> 2d output [miniBatchSize, channels]

If false: - 3d (time series) input with shape [miniBatchSize, vectorSize, timeSeriesLength] -> 3d output[miniBatchSize, vectorSize, 1] - 4d (CNN) input with shape [miniBatchSize, channels, height, width] -> 2doutput [miniBatchSize, channels, 1, 1] - 5d (CNN3D) input with shape [miniBatchSize, channels, depth,height, width] -> 2d output [miniBatchSize, channels, 1, 1, 1]

• param collapseDimensions Whether to collapse the dimensions or not

pnorm

public Builder pnorm(int pnorm) 

P-norm constant. Only used if using {- link PoolingType#PNORM} for the pooling type

• param pnorm P-norm constant

LocalResponseNormalization

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Local response normalization layer See section 3.3 of http://www.cs.toronto.edu/~fritz/absps/imagenet.pdf

k

public Builder k(double k) 

LRN scaling constant k. Default: 2

n

public Builder n(double n) 

Number of adjacent kernel maps to use when doing LRN. default: 5

• param n Number of adjacent kernel maps

alpha

public Builder alpha(double alpha) 

LRN scaling constant alpha. Default: 1e-4

• param alpha Scaling constant

beta

public Builder beta(double beta) 

Scaling constant beta. Default: 0.75

• param beta Scaling constant

cudnnAllowFallback

public Builder cudnnAllowFallback(boolean allowFallback) 

When using CuDNN and an error is encountered, should fallback to the non-CuDNN implementatation be allowed?If set to false, an exception in CuDNN will be propagated back to the user. If false, the built-in(non-CuDNN) implementation for BatchNormalization will be used

• param allowFallback Whether fallback to non-CuDNN implementation should be used

LocallyConnected1D

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SameDiff version of a 1D locally connected layer.

nIn

public Builder nIn(int nIn) 

Number of inputs to the layer (input size)

nOut

public Builder nOut(int nOut) 

• param nOut Number of outputs (output size)

activation

public Builder activation(Activation activation) 

• param activation Activation function for the layer

kernelSize

public Builder kernelSize(int k) 

• param k Kernel size for the layer

stride

public Builder stride(int s) 

• param s Stride for the layer

padding

public Builder padding(int p) 

• param p Padding for the layer. Not used if {- link ConvolutionMode#Same} is set

convolutionMode

public Builder convolutionMode(ConvolutionMode cm) 

• param cm Convolution mode for the layer. See {- link ConvolutionMode} for details

dilation

public Builder dilation(int d) 

• param d Dilation for the layer

hasBias

public Builder hasBias(boolean hasBias) 

• param hasBias If true (default is false) the layer will have a bias

setInputSize

public Builder setInputSize(int inputSize) 

Set input filter size for this locally connected 1D layer

• param inputSize height of the input filters
• return Builder

LocallyConnected2D

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SameDiff version of a 2D locally connected layer.

setKernel

public void setKernel(int... kernel) 

Number of inputs to the layer (input size)

setStride

public void setStride(int... stride) 

• param stride Stride for the layer. Must be 2 values (height/width)

setPadding

public void setPadding(int... padding) 

• param padding Padding for the layer. Not used if {- link ConvolutionMode#Same} is set. Must be 2 values (height/width)

setDilation

public void setDilation(int... dilation) 

• param dilation Dilation for the layer. Must be 2 values (height/width)

nIn

public Builder nIn(int nIn) 

• param nIn Number of inputs to the layer (input size)

nOut

public Builder nOut(int nOut) 

• param nOut Number of outputs (output size)

activation

public Builder activation(Activation activation) 

• param activation Activation function for the layer

kernelSize

public Builder kernelSize(int... k) 

• param k Kernel size for the layer. Must be 2 values (height/width)

stride

public Builder stride(int... s) 

• param s Stride for the layer. Must be 2 values (height/width)

padding

public Builder padding(int... p) 

• param p Padding for the layer. Not used if {- link ConvolutionMode#Same} is set. Must be 2 values (height/width)

convolutionMode

public Builder convolutionMode(ConvolutionMode cm) 

• param cm Convolution mode for the layer. See {- link ConvolutionMode} for details

dilation

public Builder dilation(int... d) 

• param d Dilation for the layer. Must be 2 values (height/width)

hasBias

public Builder hasBias(boolean hasBias) 

• param hasBias If true (default is false) the layer will have a bias

setInputSize

public Builder setInputSize(int... inputSize) 

Set input filter size (h,w) for this locally connected 2D layer

• param inputSize pair of height and width of the input filters to this layer
• return Builder

LossLayer

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LossLayer is a flexible output layer that performs a loss function on an input without MLP logic. LossLayer isdoes not have any parameters. Consequently, setting nIn/nOut isn’t supported - the output size is the same size asthe input activations.

nIn

public Builder nIn(int nIn) 

• param lossFunction Loss function for the loss layer

OutputLayer

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Output layer used for training via backpropagation based on labels and a specified loss function. Can be configuredfor both classification and regression. Note that OutputLayer has parameters - it contains a fully-connected layer(effectively contains a DenseLayer) internally. This allows the output size to be different to the layer input size.

build

public OutputLayer build() 

• param lossFunction Loss function for the output layer

Pooling1D

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Supports the following pooling types: MAX, AVG, SUM, PNORM, NONE

Pooling2D

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Supports the following pooling types: MAX, AVG, SUM, PNORM, NONE

Subsampling1DLayer

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sequenceLength]}. This layer accepts RNN InputTypes instead of CNN InputTypes.

Supports the following pooling types: MAX, AVG, SUM, PNORM

setKernelSize

public void setKernelSize(int... kernelSize) 

Kernel size

• param kernelSize kernel size

setStride

public void setStride(int... stride) 

Stride

• param stride stride value

setPadding

public void setPadding(int... padding) 

Padding

• param padding padding value

Upsampling1D

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sequenceLength]} Example:

If input (for a single example, with channels down page, and sequence from left to right) is:
[ A1, A2, A3]
[ B1, B2, B3]
Then output with size = 2 is:
[ A1, A1, A2, A2, A3, A3]
[ B1, B1, B2, B2, B3, B2]

size

public Builder size(int size) 

Upsampling size

• param size upsampling size in single spatial dimension of this 1D layer

size

public Builder size(int[] size) 

Upsampling size int array with a single element. Array must be length 1

• param size upsampling size in single spatial dimension of this 1D layer

Upsampling2D

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Upsampling 2D layer Repeats each value (or rather, set of depth values) in the height and width dimensions by

Input (slice for one example and channel)
[ A, B ]
[ C, D ]
Size = [2, 2]
Output (slice for one example and channel)
[ A, A, B, B ]
[ A, A, B, B ]
[ C, C, D, D ]
[ C, C, D, D ]

size

public Builder size(int size) 

Upsampling size int, used for both height and width

• param size upsampling size in height and width dimensions

size

public Builder size(int[] size) 

Upsampling size array

• param size upsampling size in height and width dimensions

Upsampling3D

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Upsampling 3D layer Repeats each value (all channel values for each x/y/z location) by size[0], size[1] and[minibatch, channels, size[0] depth, size[1] height, size[2] width]}

size

public Builder size(int size) 

Upsampling size as int, so same upsampling size is used for depth, width and height

• param size upsampling size in height, width and depth dimensions

size

public Builder size(int[] size) 

Upsampling size as int, so same upsampling size is used for depth, width and height

• param size upsampling size in height, width and depth dimensions

ZeroPadding1DLayer

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Zero padding 1D layer for convolutional neural networks. Allows padding to be done separately for top and bottom.

setPadding

public void setPadding(int... padding) 

Padding value for left and right. Must be length 2 array

build

public ZeroPadding1DLayer build() 

• param padding Padding for both the left and right

ZeroPadding3DLayer

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Zero padding 3D layer for convolutional neural networks. Allows padding to be done separately for “left” and “right”in all three spatial dimensions.

setPadding

public void setPadding(int... padding) 

[padLeftD, padRightD, padLeftH, padRightH, padLeftW, padRightW]

build

public ZeroPadding3DLayer build() 

• param padding Padding for both the left and right in all three spatial dimensions

ZeroPaddingLayer

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Zero padding layer for convolutional neural networks (2D CNNs). Allows padding to be done separately fortop/bottom/left/right

setPadding

public void setPadding(int... padding) 

Padding value for top, bottom, left, and right. Must be length 4 array

build

public ZeroPaddingLayer build() 

• param padHeight Padding for both the top and bottom
• param padWidth Padding for both the left and right

ElementWiseMultiplicationLayer

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is a learnable weight vector of length nOut - “.” is element-wise multiplication - b is a bias vectorNote that the input and output sizes of the element-wise layer are the same for this layer

created by jingshu

getMemoryReport

public LayerMemoryReport getMemoryReport(InputType inputType) 

This is a report of the estimated memory consumption for the given layer

• param inputType Input type to the layer. Memory consumption is often a function of the input type
• return Memory report for the layer

RepeatVector

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RepeatVector layer configuration.

RepeatVector takes a mini-batch of vectors of shape (mb, length) and a repeat factor n and outputs a 3D tensor ofshape (mb, n, length) in which x is repeated n times.

getRepetitionFactor

public int getRepetitionFactor() 

Set repetition factor for RepeatVector layer

setRepetitionFactor

public void setRepetitionFactor(int n) 

Set repetition factor for RepeatVector layer

• param n upsampling size in height and width dimensions

repetitionFactor

public Builder repetitionFactor(int n) 

Set repetition factor for RepeatVector layer

• param n upsampling size in height and width dimensions

Yolo2OutputLayer

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Output (loss) layer for YOLOv2 object detection model, based on the papers: YOLO9000: Better, Faster, Stronger -Redmon & Farhadi (2016) - https://arxiv.org/abs/1612.08242 andYou Only Look Once: Unified, Real-Time Object Detection - Redmon et al. (2016) -http://www.cv-foundation.org/openaccess/content_cvpr_2016/papers/Redmon_You_Only_Look_CVPR_2016_paper.pdfThis loss function implementation is based on the YOLOv2 version of the paper. However, note that it doesn’tcurrently support simultaneous training on both detection and classification datasets as described in the YOlO9000paper.

Note: Input activations to the Yolo2OutputLayer should have shape: [minibatch, b(5+c), H, W], where: b = numberof bounding boxes (determined by config - see papers for details) c = number of classes H = output/labelheight W = output/label widthImportant: In practice, this means that the last convolutional layer before your Yolo2OutputLayer should have outputdepth of b(5+c). Thus if you change the number of bounding boxes, or change the number of object classes, the numberof channels (nOut of the last convolution layer) needs to also change.Label format: [minibatch, 4+C, H, W] Order for labels depth: [x1,y1,x2,y2,(class labels)] x1 = box top leftposition y1 = as above, y axis x2 = box bottom right position y2 = as above y axis Note: labels arerepresented as a multiple of grid size - for a 13x13 grid, (0,0) is top left, (13,13) is bottom right Note alsothat mask arrays are not required - this implementation infers the presence or absence of objects in each grid cellfrom the class labels (which should be 1-hot if an object is present, or all 0s otherwise).

lambdaCoord

public Builder lambdaCoord(double lambdaCoord) 

Loss function coefficient for position and size/scale components of the loss function. Default (as perpaper): 5

lambbaNoObj

public Builder lambbaNoObj(double lambdaNoObj) 

Loss function coefficient for the “no object confidence” components of the loss function. Default (as perpaper): 0.5

• param lambdaNoObj Lambda value for no-object (confidence) component of the loss function

lossPositionScale

public Builder lossPositionScale(ILossFunction lossPositionScale) 

Loss function for position/scale component of the loss function

• param lossPositionScale Loss function for position/scale

lossClassPredictions

public Builder lossClassPredictions(ILossFunction lossClassPredictions) 

Loss function for the class predictions - defaults to L2 loss (i.e., sum of squared errors, as per thepaper), however Loss MCXENT could also be used (which is more common for classification).

• param lossClassPredictions Loss function for the class prediction error component of the YOLO loss function

boundingBoxPriors

public Builder boundingBoxPriors(INDArray boundingBoxes) 

Bounding box priors dimensions [width, height]. For N bounding boxes, input has shape [rows, columns] = [N,2] Note that dimensions should be specified as fraction of grid size. For example, a network with 13x13output, a value of 1.0 would correspond to one grid cell; a value of 13 would correspond to the entireimage.

• param boundingBoxes Bounding box prior dimensions (width, height)

MaskLayer

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MaskLayer applies the mask array to the forward pass activations, and backward pass gradients, passing throughthis layer. It can be used with 2d (feed-forward), 3d (time series) or 4d (CNN) activations.

MaskZeroLayer

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Wrapper which masks timesteps with activation equal to the specified masking value (0.0 default). Assumes that theinput shape is [batch_size, input_size, timesteps].