3-D global average pooling layer
A 3-D global average pooling layer performs downsampling by computing the mean of the height, width, and depth dimensions of the input.
NumInputs— Number of inputs
Number of inputs of the layer. This layer accepts a single input only.
InputNames— Input names
Input names of the layer. This layer accepts a single input only.
NumOutputs— Number of outputs
Number of outputs of the layer. This layer has a single output only.
OutputNames— Output names
Output names of the layer. This layer has a single output only.
Create a 3-D global average pooling layer with the name
layer = globalAveragePooling3dLayer('Name','gap1')
layer = GlobalAveragePooling3DLayer with properties: Name: 'gap1'
Include a 3-D global average pooling layer in a
layers = [ ... image3dInputLayer([28 28 28 3]) convolution3dLayer(5,20) reluLayer globalAveragePooling3dLayer fullyConnectedLayer(10) softmaxLayer classificationLayer]
layers = 7x1 Layer array with layers: 1 '' 3-D Image Input 28x28x28x3 images with 'zerocenter' normalization 2 '' Convolution 20 5x5x5 convolutions with stride [1 1 1] and padding [0 0 0; 0 0 0] 3 '' ReLU ReLU 4 '' 3-D Global Average Pooling 3-D global average pooling 5 '' Fully Connected 10 fully connected layer 6 '' Softmax softmax 7 '' Classification Output crossentropyex
In an image classification network, you can use a
globalAveragePooling3dLayer before the final fully connected layer to
reduce the size of the activations without sacrificing performance. The reduced size of
the activations means that the downstream fully connected layers will have fewer weights,
reducing the size of your network.
You can use a
globalAveragePooling3dLayer towards the end of a
classification network instead of a
fullyConnectedLayer. Since global pooling layers have no learnable parameters,
they can be less prone to overfitting and can reduce the size of the network. These
networks can also be more robust to spatial translations of input data. You can also
replace a fully connected layer with a
globalMaxPooling3dLayer instead. Whether a
globalMaxPooling3dLayer or a
globalAveragePooling3dLayer is more appropriate depends on your data
To use a global average pooling layer instead of a fully connected layer, the size of
the input to
globalAveragePooling3dLayer must match the number of
classes in the classification problem