activations
(Not recommended) Compute deep learning network layer activations
activations
is not recommended. Use the minibatchpredict
function instead and specify the
Outputs
option. For more information, see Version
History.
Syntax
Description
You can compute deep learning network layer activations on either a CPU or
GPU. Using a GPU requires
a Parallel Computing Toolbox™ license and a supported GPU device. For information about supported devices, see
GPU Computing Requirements (Parallel Computing Toolbox). Specify the hardware requirements using the
ExecutionEnvironment
name-value argument.
returns network activations with additional options specified by one or more
name-value pair arguments. For example, act
= activations(___,Name=Value
)OutputAs="rows"
specifies the activation output format as "rows"
. Use this
syntax with any of the input arguments in previous syntaxes. Specify name-value
arguments after all other input arguments.
Examples
Visualize Network Activations
Visualize the activations of a neural network.
Load a pretrained SqueezeNet neural network.
net = squeezenet;
Read an example image.
I = imread("peppers.png");
Evaluate the network activations for the layer with the name
"fire2-squeeze1x1"
.
act = activations(net,I,"fire2-squeeze1x1");
Display the activations for each channel.
act = mat2gray(act); act = imtile(act); figure imshow(act)
Input Arguments
net
— Trained network
SeriesNetwork
object | DAGNetwork
object
Trained network, specified as a SeriesNetwork
or a DAGNetwork
object. You can get a trained network by importing a pretrained network (for example, by
using the googlenet
function) or by training your own network using
trainNetwork
.
images
— Image data
datastore | numeric array | table
Image data, specified as one of the following.
Data Type | Description | Example Usage | |
---|---|---|---|
Datastore | ImageDatastore | Datastore of images saved on disk | Make predictions with images saved on disk, where the images are the same size. When the images are different sizes, use an
|
AugmentedImageDatastore | Datastore that applies random affine geometric transformations, including resizing, rotation, reflection, shear, and translation | Make predictions with images saved on disk, where the images are different sizes. | |
TransformedDatastore | Datastore that transforms batches of data read from an underlying datastore using a custom transformation function |
| |
CombinedDatastore | Datastore that reads from two or more underlying datastores |
| |
Custom mini-batch datastore | Custom datastore that returns mini-batches of data | Make predictions using data in a format that other datastores do not support. For details, see Develop Custom Mini-Batch Datastore. | |
Numeric array | Images specified as a numeric array | Make predictions using data that fits in memory and does not require additional processing like resizing. | |
Table | Images specified as a table | Make predictions using data stored in a table. |
When you use a datastore with networks with multiple inputs, the datastore must be a
TransformedDatastore
or
CombinedDatastore
object.
Tip
For sequences of images, for example, video data, use the sequences
input argument.
Datastore
Datastores read mini-batches of images and responses. Use datastores when you have data that does not fit in memory or when you want to resize the input data.
These datastores are directly compatible with activations
for image data.:
Custom mini-batch datastore. For details, see Develop Custom Mini-Batch Datastore.
Tip
Use augmentedImageDatastore
for efficient preprocessing of images for deep
learning, including image resizing. Do not use the ReadFcn
option of
ImageDatastore
objects.
ImageDatastore
allows batch reading of JPG or PNG image files
using prefetching. If you set the ReadFcn
option to a custom
function, then ImageDatastore
does not prefetch and is usually
significantly slower.
You can use other built-in datastores for making predictions by using the transform
and
combine
functions. These functions can convert the data read from datastores to the format required
by classify
.
The required format of the datastore output depends on the network architecture.
Network Architecture | Datastore Output | Example Output |
---|---|---|
Single input | Table or cell array, where the first column specifies the predictors. Table elements must be scalars, row vectors, or 1-by-1 cell arrays containing a numeric array. Custom datastores must output tables. |
data = read(ds) data = 4×1 table Predictors __________________ {224×224×3 double} {224×224×3 double} {224×224×3 double} {224×224×3 double} |
data = read(ds) data = 4×1 cell array {224×224×3 double} {224×224×3 double} {224×224×3 double} {224×224×3 double} | ||
Multiple input | Cell array with at least The
first The order of inputs is given by the
|
data = read(ds) data = 4×2 cell array {224×224×3 double} {128×128×3 double} {224×224×3 double} {128×128×3 double} {224×224×3 double} {128×128×3 double} {224×224×3 double} {128×128×3 double} |
The format of the predictors depends on the type of data.
Data | Format |
---|---|
2-D images | h-by-w-by-c numeric array, where h, w, and c are the height, width, and number of channels of the images, respectively |
3-D images | h-by-w-by-d-by-c numeric array, where h, w, d, and c are the height, width, depth, and number of channels of the images, respectively |
For more information, see Datastores for Deep Learning.
Numeric Array
For data that fits in memory and does not require additional processing like augmentation, you can specify a data set of images as a numeric array.
The size and shape of the numeric array depends on the type of image data.
Data | Format |
---|---|
2-D images | h-by-w-by-c-by-N numeric array, where h, w, and c are the height, width, and number of channels of the images, respectively, and N is the number of images |
3-D images | h-by-w-by-d-by-c-by-N numeric array, where h, w, d, and c are the height, width, depth, and number of channels of the images, respectively, and N is the number of images |
Table
As an alternative to datastores or numeric arrays, you can also specify images in a table.
When you specify images in a table, each row in the table corresponds to an observation.
For image input, the predictors must be in the first column of the table, specified as one of the following:
Absolute or relative file path to an image, specified as a character vector
1-by-1 cell array containing a h-by-w-by-c numeric array representing a 2-D image, where h, w, and c correspond to the height, width, and number of channels of the image, respectively
Tip
This argument supports complex-valued predictors. To input complex-valued data into a
SeriesNetwork
or DAGNetwork
object, the
SplitComplexInputs
option of the input layer must be
1
(true
).
sequences
— Sequence or time series data
datastore | cell array of numeric arrays | numeric array
Sequence or time series data, specified as one of the following.
Data Type | Description | Example Usage | |
---|---|---|---|
Datastore | TransformedDatastore | Datastore that transforms batches of data read from an underlying datastore using a custom transformation function |
|
CombinedDatastore | Datastore that reads from two or more underlying datastores |
| |
Custom mini-batch datastore | Custom datastore that returns mini-batches of data | Make predictions using data in a format that other datastores do not support. For details, see Develop Custom Mini-Batch Datastore. | |
Numeric or cell array | A single sequence specified as a numeric array or a data set of sequences specified as cell array of numeric arrays | Make predictions using data that fits in memory and does not require additional processing like custom transformations. |
Datastore
Datastores read mini-batches of sequences and responses. Use datastores when you have data that does not fit in memory or when you want to apply transformations to the data.
These datastores are directly compatible with activations
for
sequence data:
Custom mini-batch datastore. For details, see Develop Custom Mini-Batch Datastore.
You can use other built-in datastores for making predictions by using
the transform
and combine
functions. These functions can convert the data read from
datastores to the table or cell array format required by
activations
. For example, you can transform and combine
data read from in-memory arrays and CSV files using an
ArrayDatastore
and an TabularTextDatastore
object, respectively.
The datastore must return data in a table or cell array. Custom mini-batch datastores must output tables.
Datastore Output | Example Output |
---|---|
Table |
data = read(ds) data = 4×2 table Predictors __________________ {12×50 double} {12×50 double} {12×50 double} {12×50 double} |
Cell array |
data = read(ds) data = 4×2 cell array {12×50 double} {12×50 double} {12×50 double} {12×50 double} |
The format of the predictors depends on the type of data.
Data | Format of Predictors |
---|---|
Vector sequence | c-by-s matrix, where c is the number of features of the sequence and s is the sequence length |
1-D image sequence | h-by-c-by-s array, where h and c correspond to the height and number of channels of the image, respectively, and s is the sequence length. Each sequence in the mini-batch must have the same sequence length. |
2-D image sequence | h-by-w-by-c-by-s array, where h, w, and c correspond to the height, width, and number of channels of the image, respectively, and s is the sequence length. Each sequence in the mini-batch must have the same sequence length. |
3-D image sequence | h-by-w-by-d-by-c-by-s array, where h, w, d, and c correspond to the height, width, depth, and number of channels of the image, respectively, and s is the sequence length. Each sequence in the mini-batch must have the same sequence length. |
For predictors returned in tables, the elements must contain a numeric scalar, a numeric row vector, or a 1-by-1 cell array containing a numeric array.
For more information, see Datastores for Deep Learning.
Numeric or Cell Array
For data that fits in memory and does not require additional processing like custom transformations, you can specify a single sequence as a numeric array or a data set of sequences as a cell array of numeric arrays.
For cell array input, the cell array must be an N-by-1 cell array of numeric arrays, where N is the number of observations. The size and shape of the numeric array representing a sequence depends on the type of sequence data.
Input | Description |
---|---|
Vector sequences | c-by-s matrices, where c is the number of features of the sequences and s is the sequence length |
1-D image sequences | h-by-c-by-s arrays, where h and c correspond to the height and number of channels of the images, respectively, and s is the sequence length |
2-D image sequences | h-by-w-by-c-by-s arrays, where h, w, and c correspond to the height, width, and number of channels of the images, respectively, and s is the sequence length |
3-D image sequences | h-by-w-by-d-by-c-by-s, where h, w, d, and c correspond to the height, width, depth, and number of channels of the 3-D images, respectively, and s is the sequence length |
Tip
This argument supports complex-valued predictors. To input complex-valued data
into a SeriesNetwork
or DAGNetwork
object, the
SplitComplexInputs
option of the input layer must be
1
(true
).
features
— Feature data
datastore | numeric array | table
Feature data, specified as one of the following.
Data Type | Description | Example Usage | |
---|---|---|---|
Datastore | TransformedDatastore | Datastore that transforms batches of data read from an underlying datastore using a custom transformation function |
|
CombinedDatastore | Datastore that reads from two or more underlying datastores |
| |
Custom mini-batch datastore | Custom datastore that returns mini-batches of data | Make predictions using data in a format that other datastores do not support. For details, see Develop Custom Mini-Batch Datastore. | |
Table | Feature data specified as a table | Make predictions using data stored in a table. | |
Numeric array | Feature data specified as numeric array | Make predictions using data that fits in memory and does not require additional processing like custom transformations. |
Datastore
Datastores read mini-batches of feature data and responses. Use datastores when you have data that does not fit in memory or when you want to apply transformations to the data.
These datastores are directly compatible with activations
for
feature data:
Custom mini-batch datastore. For details, see Develop Custom Mini-Batch Datastore.
You can use other built-in datastores for making predictions by using the transform
and
combine
functions. These functions can convert the data read from datastores to the table or cell
array format required by activations
. For more information, see Datastores for Deep Learning.
For networks with multiple inputs, the datastore must be a TransformedDatastore
or
CombinedDatastore
object.
The datastore must return data in a table or a cell array. Custom mini-batch datastores must output tables. The format of the datastore output depends on the network architecture.
Network Architecture | Datastore Output | Example Output |
---|---|---|
Single input layer | Table or cell array with at least one column, where the first column specifies the predictors. Table elements must be scalars, row vectors, or 1-by-1 cell arrays containing a numeric array. Custom mini-batch datastores must output tables. | Table for network with one input: data = read(ds) data = 4×2 table Predictors __________________ {24×1 double} {24×1 double} {24×1 double} {24×1 double} |
Cell array for network with one input:
data = read(ds) data = 4×1 cell array {24×1 double} {24×1 double} {24×1 double} {24×1 double} | ||
Multiple input layers | Cell array with at least The
first The order of inputs is given by the
| Cell array for network with two inputs: data = read(ds) data = 4×3 cell array {24×1 double} {28×1 double} {24×1 double} {28×1 double} {24×1 double} {28×1 double} {24×1 double} {28×1 double} |
The predictors must be c-by-1 column vectors, where c is the number of features.
For more information, see Datastores for Deep Learning.
Table
For feature data that fits in memory and does not require additional processing like custom transformations, you can specify feature data and responses as a table.
Each row in the table corresponds to an observation. The arrangement of predictors in the table columns depends on the type of task.
Task | Predictors |
---|---|
Feature classification | Features specified in one or more columns as scalars. |
Numeric Array
For feature data that fits in memory and does not require additional processing like custom transformations, you can specify feature data as a numeric array.
The numeric array must be an
N-by-numFeatures
numeric array, where
N is the number of observations and numFeatures
is
the number of features of the input data.
Tip
This argument supports complex-valued predictors. To input complex-valued data into a
SeriesNetwork
or DAGNetwork
object, the
SplitComplexInputs
option of the input layer must be
1
(true
).
X1,...,XN
— Numeric or cell arrays for networks with multiple inputs
numeric array | cell array
Numeric or cell arrays for networks with multiple inputs.
For image, sequence, and feature predictor input, the format of the predictors must
match the formats described in the images
,
sequences
, or features
argument
descriptions, respectively.
For an example showing how to train a network with multiple inputs, see Train Network on Image and Feature Data.
To input complex-valued data into a DAGNetwork
or
SeriesNetwork
object, the SplitComplexInputs
option of the input layer must be 1
(true
).
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
| cell
Complex Number Support: Yes
mixed
— Mixed data
TransformedDatastore
| CombinedDatastore
| custom mini-batch datastore
Mixed data, specified as one of the following.
Data Type | Description | Example Usage |
---|---|---|
TransformedDatastore | Datastore that transforms batches of data read from an underlying datastore using a custom transformation function |
|
CombinedDatastore | Datastore that reads from two or more underlying datastores |
|
Custom mini-batch datastore | Custom datastore that returns mini-batches of data | Make predictions using data in a format that other datastores do not support. For details, see Develop Custom Mini-Batch Datastore. |
You can use other built-in datastores for making predictions by using the transform
and combine
functions. These functions can convert the data read from datastores to the table or cell array format required by activations
. For more information, see Datastores for Deep Learning.
The datastore must return data in a table or a cell array. Custom mini-batch datastores must output tables. The format of the datastore output depends on the network architecture.
Datastore Output | Example Output |
---|---|
Cell array with The
order of inputs is given by the |
data = read(ds) data = 4×3 cell array {24×1 double} {28×1 double} {24×1 double} {28×1 double} {24×1 double} {28×1 double} {24×1 double} {28×1 double} |
For image, sequence, and feature predictor input, the format of the predictors must match
the formats described in the images
, sequences
, or
features
argument descriptions, respectively.
For an example showing how to train a network with multiple inputs, see Train Network on Image and Feature Data.
Tip
To convert a numeric array to a datastore, use arrayDatastore
.
layer
— Layer to extract activations from
numeric index | character vector
Layer to extract activations from, specified as a numeric index or a character vector.
To compute the activations of a SeriesNetwork
object, specify the layer using its numeric
index, or as a character vector corresponding to the layer name.
To compute the activations of a DAGNetwork
object, specify the layer as the character vector
corresponding to the layer name. If the layer has multiple outputs, specify
the layer and output as the layer name, followed by the character “/”,
followed by the name of the layer output. That is,
layer
is of the form
'layerName/outputName'
.
Example: 3
Example: 'conv1'
Example: 'mpool/out'
Name-Value Arguments
Specify optional pairs of arguments as
Name1=Value1,...,NameN=ValueN
, where Name
is
the argument name and Value
is the corresponding value.
Name-value arguments must appear after other arguments, but the order of the
pairs does not matter.
Before R2021a, use commas to separate each name and value, and enclose
Name
in quotes.
Example: MiniBatchSize=256
specifies the mini-batch size as
256.
OutputAs
— Format of output activations
"channels"
(default) | "rows"
| "columns"
Format of output activations, specified as
"channels"
, "rows"
, or
"columns"
. For descriptions of the output
formats, see act
.
For image input, if the OutputAs
option is
"channels"
, then the images in the input data can
be larger than the input size of the image input layer of the network.
For other output formats, the images in the input must have the same
size as the input size of the image input layer of the network.
MiniBatchSize
— Size of mini-batches
128
(default) | positive integer
Size of mini-batches to use for prediction, specified as a positive integer. Larger mini-batch sizes require more memory, but can lead to faster predictions.
SequenceLength
— Option to pad, truncate, or split sequences
"longest"
(default) | "shortest"
| positive integer
Option to pad, truncate, or split sequences, specified as one of these values:
"longest"
— Pad sequences in each mini-batch to have the same length as the longest sequence. This option does not discard any data, though padding can introduce noise to the neural network."shortest"
— Truncate sequences in each mini-batch to have the same length as the shortest sequence. This option ensures that no padding is added, at the cost of discarding data.Positive integer — For each mini-batch, pad the sequences to the length of the longest sequence in the mini-batch, and then split the sequences into smaller sequences of the specified length. If splitting occurs, then the software creates extra mini-batches. If the specified sequence length does not evenly divide the sequence lengths of the data, then the mini-batches containing the ends those sequences have length shorter than the specified sequence length. Use this option if the full sequences do not fit in memory. Alternatively, try reducing the number of sequences per mini-batch by setting the
MiniBatchSize
option to a lower value.
To learn more about the effect of padding and truncating sequences, see Sequence Padding and Truncation.
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
| char
| string
SequencePaddingValue
— Value to pad sequences
0
(default) | scalar
Value by which to pad input sequences, specified as a scalar.
Do not pad sequences with NaN
, because doing so can propagate errors throughout the neural network.
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
SequencePaddingDirection
— Direction of padding or truncation
"right"
(default) | "left"
Direction of padding or truncation, specified as one of the following:
"right"
— Pad or truncate sequences on the right. The sequences start at the same time step and the software truncates or adds padding to the end of the sequences."left"
— Pad or truncate sequences on the left. The software truncates or adds padding to the start of the sequences so that the sequences end at the same time step.
Because recurrent layers process sequence data one time step at a time, when the recurrent layer OutputMode
property is "last"
, any padding in the final time steps can negatively influence the layer output. To pad or truncate sequence data on the left, set the SequencePaddingDirection
option to "left"
.
For sequence-to-sequence neural networks (when the OutputMode
property is "sequence"
for each recurrent layer), any padding in the first time steps can negatively influence the predictions for the earlier time steps. To pad or truncate sequence data on the right, set the SequencePaddingDirection
option to "right"
.
To learn more about the effect of padding and truncating sequences, see Sequence Padding and Truncation.
Acceleration
— Performance optimization
"auto"
(default) | "mex"
| "none"
Performance optimization, specified as one of the following:
"auto"
— Automatically apply a number of optimizations suitable for the input network and hardware resources."mex"
— Compile and execute a MEX function. This option is available only when you use a GPU. Using a GPU requires a Parallel Computing Toolbox license and a supported GPU device. For information about supported devices, see GPU Computing Requirements (Parallel Computing Toolbox). If Parallel Computing Toolbox or a suitable GPU is not available, then the software returns an error."none"
— Disable all acceleration.
If Acceleration
is "auto"
, then MATLAB® applies a number of compatible optimizations and does not generate a MEX
function.
The "auto"
and "mex"
options can offer performance
benefits at the expense of an increased initial run time. Subsequent calls with
compatible parameters are faster. Use performance optimization when you plan to call the
function multiple times using new input data.
The "mex"
option generates and executes a MEX function based on the network
and parameters used in the function call. You can have several MEX functions associated
with a single network at one time. Clearing the network variable also clears any MEX
functions associated with that network.
The "mex"
option supports networks that contain the layers listed
on the Supported Layers (GPU Coder) page, except for
sequenceInputLayer
objects.
The "mex"
option is available when you use a single GPU.
To use the "mex"
option, you must have a C/C++ compiler installed
and the GPU Coder™ Interface for Deep Learning support package. Install the support package using the Add-On Explorer in
MATLAB. For setup instructions, see MEX Setup (GPU Coder). GPU Coder is not required.
For quantized networks, the "mex"
option requires a CUDA® enabled NVIDIA® GPU with compute capability 6.1, 6.3, or higher.
MATLAB
Compiler™ does not support deploying networks when you use the
"mex"
option.
ExecutionEnvironment
— Hardware resource
"auto"
(default) | "gpu"
| "cpu"
| "multi-gpu"
| "parallel"
Hardware resource, specified as one of the following:
"auto"
— Use a GPU if one is available; otherwise, use the CPU."gpu"
— Use the GPU. Using a GPU requires a Parallel Computing Toolbox license and a supported GPU device. For information about supported devices, see GPU Computing Requirements (Parallel Computing Toolbox). If Parallel Computing Toolbox or a suitable GPU is not available, then the software returns an error."cpu"
— Use the CPU."multi-gpu"
— Use multiple GPUs on one machine, using a local parallel pool based on your default cluster profile. If there is no current parallel pool, the software starts a parallel pool with pool size equal to the number of available GPUs."parallel"
— Use a local or remote parallel pool based on your default cluster profile. If there is no current parallel pool, the software starts one using the default cluster profile. If the pool has access to GPUs, then only workers with a unique GPU perform computation. If the pool does not have GPUs, then computation takes place on all available CPU workers instead.
For more information on when to use the different execution environments, see Scale Up Deep Learning in Parallel, on GPUs, and in the Cloud.
The "gpu"
, "multi-gpu"
, and
"parallel"
options require Parallel Computing Toolbox. To use a GPU for deep
learning, you must also have a supported GPU device. For information on supported devices, see
GPU Computing Requirements (Parallel Computing Toolbox). If you choose one of these options and Parallel Computing Toolbox or a suitable GPU is not available, then the software returns an
error.
To make predictions in parallel with networks with recurrent layers (by setting
ExecutionEnvironment
to either "multi-gpu"
or "parallel"
), the SequenceLength
option must
be "shortest"
or "longest"
.
Networks with custom layers that contain State
parameters do not
support making predictions in parallel.
Output Arguments
act
— Activations from network layer
numeric array | cell array
Activations from the network layer, returned as a numeric array or a cell
array of numeric arrays. The format of act
depends on
the type of input data, the type of layer output, and the specified
OutputAs
option.
Image or Folded Sequence Output
If the layer outputs image or folded sequence data, then
act
is a numeric array.
OutputAs | act |
---|---|
"channels" | For 2-D image output,
For 3-D
image output, For
folded 2-D image sequence output,
For folded 3-D image
sequence output, |
"rows" | For 2-D and 3-D image output,
For folded 2-D and 3-D image
sequence output, |
"columns" | For 2-D and 3-D image output,
For folded 2-D and 3-D image
sequence output, |
Sequence Output
If layer
has sequence output (for example, LSTM
layers with the output mode "sequence"
), then
act
is a cell array. In this case, the
"OutputAs"
option must be
"channels"
.
OutputAs | act |
---|---|
"channels" | For vector sequence output,
For 2-D image sequence output,
For 3-D image
sequence output, In these cases,
|
Feature Vector and Single Time Step Output
If layer
outputs a feature vector or a single
time step of a sequence (for example, an LSTM layer with the output mode
"last"
), then act
is a
numeric array.
OutputAs | act |
---|---|
"channels" | For a feature vector or single time step
containing vector data, For a single time
step containing 2-D image data,
For a single
time step containing 3-D image data,
|
"rows" | n-by-m
matrix, where n is the number of
observations and m is the
number of output elements from the chosen layer. In
this case, act(i,:) contains the
activations for the i th
sequence. |
"columns" | m-by-n
matrix, where m is the number of
output elements from the chosen layer and
n is the number of
observations. In this case,
act(:,i) contains the
activations for the i th
image. |
Algorithms
Floating-Point Arithmetic
When you train a neural network using the trainnet
or trainNetwork
functions, or when you use prediction or validation functions with DAGNetwork
and SeriesNetwork
objects, the software performs these computations using single-precision, floating-point arithmetic. Functions for prediction and validation include predict
, classify
, and activations
. The software uses single-precision arithmetic when you train neural networks using both CPUs and GPUs.
Reproducibility
To provide the best performance, deep learning using a GPU in MATLAB is not guaranteed to be deterministic. Depending on your network architecture, under some conditions you might get different results when using a GPU to train two identical networks or make two predictions using the same network and data.
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.
Usage notes and limitations:
C++ code generation supports the following syntaxes:
act = activations(net,images,layer)
, whereimages
is a numeric arrayact = activations(net,sequences,layer)
, wheresequences
is a cell arrayact = activations(net,features,layer)
, wherefeatures
is a numeric arrayact = activations(__,Name,Value)
using any of the previous syntaxes
For numeric inputs, the input must not have variable size. The size of the input must be fixed at code generation time.
For vector sequence inputs, the number of features must be a constant during code generation. The sequence length can be variable sized.
For image sequence inputs, the height, width, and the number of channels must be a constant during code generation.
The
layer
argument must be a constant during code generation.Only the
OutputAs
,MiniBatchSize
,SequenceLength
,SequencePaddingDirection
, andSequencePaddingValue
name-value pair arguments are supported for code generation. All name-value pairs must be compile-time constants.The format of the output activations must be
"channels"
.Only the
"longest"
and"shortest"
option of theSequenceLength
name-value pair is supported for code generation.Code generation for Intel® MKL-DNN target does not support the combination of
SequenceLength="longest"
,SequencePaddingDirection="left"
, andSequencePaddingValue=0
name-value arguments.
For more information about generating code for deep learning neural networks, see Workflow for Deep Learning Code Generation with MATLAB Coder (MATLAB Coder).
GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.
Usage notes and limitations:
GPU code generation supports the following syntaxes:
act = activations(net,images,layer)
, whereimages
is a numeric arrayact = activations(net,sequences,layer)
, wheresequences
is a cell array or numeric arrayact = activations(net,features,layer)
, wherefeatures
is a numeric arrayact = activations(__,Name,Value)
using any of the previous syntaxes
For numeric inputs, the input must not have variable size. The size of the input must be fixed at code generation time.
GPU code generation does not support
gpuArray
inputs to theactivations
function.The cuDNN library supports vector and 2-D image sequences. The TensorRT library support only vector input sequences. The ARM®
Compute Library
for GPU does not support recurrent networks.For vector sequence inputs, the number of features must be a constant during code generation. The sequence length can be variable sized.
For image sequence inputs, the height, width, and the number of channels must be a constant during code generation.
The
layer
argument must be a constant during code generation.Only the
OutputAs
,MiniBatchSize
,SequenceLength
,SequencePaddingDirection
, andSequencePaddingValue
name-value pair arguments are supported for code generation. All name-value pairs must be compile-time constants.The format of the output activations must be
"channels"
.Only the
"longest"
and"shortest"
option of theSequenceLength
name-value pair is supported for code generation.GPU code generation for the
activations
function supports inputs that are defined as half-precision floating point data types. For more information, seehalf
(GPU Coder).
GPU Arrays
Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.
The
ExecutionEnvironment
option must be"auto"
or"gpu"
when the input data is:A
gpuArray
A cell array containing
gpuArray
objectsA table containing
gpuArray
objectsA datastore that outputs cell arrays containing
gpuArray
objectsA datastore that outputs tables containing
gpuArray
objects
For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).
Version History
Introduced in R2016aR2024a: Not recommended
Starting in R2024a, DAGNetwork
and SeriesNetwork
objects are not recommended, use dlnetwork
objects instead. This
recommendation means that the activations
function is also not
recommended. Use the predict
function
instead and specify the Outputs
option.
There are no plans to remove support for DAGNetwork
and
SeriesNetwork
objects. However, dlnetwork
objects have these advantages and are recommended instead:
dlnetwork
objects are a unified data type that supports network building, prediction, built-in training, visualization, compression, verification, and custom training loops.dlnetwork
objects support a wider range of network architectures that you can create or import from external platforms.The
trainnet
function supportsdlnetwork
objects, which enables you to easily specify loss functions. You can select from built-in loss functions or specify a custom loss function.Training and prediction with
dlnetwork
objects is typically faster thanLayerGraph
andtrainNetwork
workflows.
To convert a trained DAGNetwork
or SeriesNetwork
object to a dlnetwork
object, use the dag2dlnetwork
function.
This table shows a typical usage of the activations
function
and how to update your code to use dlnetwork
objects
instead.
Not Recommended | Recommended |
---|---|
act = activations(net,X,layerName); |
act = minibatchpredict(net,X,Outputs=layerName); |
R2022b: Prediction functions pad mini-batches to length of longest sequence before splitting when you specify SequenceLength
option as an integer
Starting in R2022b, when you make predictions with sequence data using the
predict
, classify
,
predictAndUpdateState
, classifyAndUpdateState
,
and activations
functions and the SequenceLength
option is an integer, the software pads sequences to the length of the longest sequence in
each mini-batch and then splits the sequences into mini-batches with the specified sequence
length. If SequenceLength
does not evenly divide the sequence length of
the mini-batch, then the last split mini-batch has a length shorter than
SequenceLength
. This behavior prevents time steps that contain only
padding values from influencing predictions.
In previous releases, the software pads mini-batches of sequences to have a length matching the nearest multiple of SequenceLength
that is greater than or equal to the mini-batch length and then splits the data. To reproduce this behavior, manually pad the input data such that the mini-batches have the length of the appropriate multiple of SequenceLength
. For sequence-to-sequence workflows, you may also need to manually remove time steps of the output that correspond to padding values.
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