Package ai.djl.training

Class Trainer

java.lang.Object

ai.djl.training.Trainer

All Implemented Interfaces:

java.lang.AutoCloseable

public class Trainer
extends java.lang.Object
implements java.lang.AutoCloseable

The Trainer interface provides a session for model training.

Trainer provides an easy, and manageable interface for training. Trainer is not thread-safe.

See the tutorials on:

• Training your first model
• Training using transfer learning
• Inference with an MXNet model

See Also:

The guide on memory management

Constructor Summary

Constructors

Constructor	Description
Trainer(Model model, TrainingConfig trainingConfig)	Creates an instance of Trainer with the given Model and TrainingConfig.

Method Summary

Modifier and Type	Method	Description
void	addMetric(java.lang.String metricName, long begin)	Helper to add a metric for a time difference.
void	close()
NDList	evaluate(NDList input)	Evaluates function of the model once on the given input NDList.
protected void	finalize()
NDList	forward(NDList input)	Applies the forward function of the model once on the given input NDList.
NDList	forward(NDList data, NDList labels)	Applies the forward function of the model once with both data and labels.
Device[]	getDevices()	Returns the devices used for training.
java.util.List<Evaluator>	getEvaluators()	Gets all Evaluators.
java.util.Optional<java.util.concurrent.ExecutorService>	getExecutorService()	Returns the ExecutorService.
Loss	getLoss()	Gets the training Loss function of the trainer.
NDManager	getManager()	Gets the NDManager from the model.
Metrics	getMetrics()	Returns the Metrics param used for benchmarking.
Model	getModel()	Returns the model used to create this trainer.
TrainingResult	getTrainingResult()	Returns the TrainingResult.
void	initialize(Shape... shapes)	Initializes the Model that the Trainer is going to train.
java.lang.Iterable<Batch>	iterateDataset(Dataset dataset)	Fetches an iterator that can iterate through the given Dataset.
GradientCollector	newGradientCollector()	Returns a new instance of GradientCollector.
void	notifyListeners(java.util.function.Consumer<TrainingListener> listenerConsumer)	Executes a method on each of the TrainingListeners.
void	setMetrics(Metrics metrics)	Attaches a Metrics param to use for benchmarking.
void	step()	Updates all of the parameters of the model once.

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Trainer

public Trainer(Model model,
               TrainingConfig trainingConfig)

Creates an instance of Trainer with the given Model and TrainingConfig.

Parameters:

model - the model the trainer will train on

trainingConfig - the configuration used by the trainer

Method Detail

initialize

public void initialize(Shape... shapes)

Initializes the Model that the Trainer is going to train.

Parameters:

shapes - an array of Shape of the inputs

iterateDataset

public java.lang.Iterable<Batch> iterateDataset(Dataset dataset)
                                         throws java.io.IOException,
                                                TranslateException

Fetches an iterator that can iterate through the given Dataset.

Parameters:

dataset - the dataset to iterate through

Returns:

an Iterable of Batch that contains batches of data from the dataset

Throws:

java.io.IOException - for various exceptions depending on the dataset

TranslateException - if there is an error while processing input

newGradientCollector

public GradientCollector newGradientCollector()

Returns a new instance of GradientCollector.

Returns:

a new instance of GradientCollector

forward

public NDList forward(NDList input)

Applies the forward function of the model once on the given input NDList.

Parameters:

input - the input NDList

Returns:

the output of the forward function

forward

public NDList forward(NDList data,
                      NDList labels)

Applies the forward function of the model once with both data and labels.

Parameters:

data - the input data NDList

labels - the input labels NDList

Returns:

the output of the forward function

evaluate

public NDList evaluate(NDList input)

Evaluates function of the model once on the given input NDList.

Parameters:

input - the input NDList

Returns:

the output of the predict function

step

public void step()

Updates all of the parameters of the model once.

getMetrics

public Metrics getMetrics()

Returns the Metrics param used for benchmarking.

Returns:

the the Metrics param used for benchmarking

setMetrics

public void setMetrics(Metrics metrics)

Attaches a Metrics param to use for benchmarking.

Parameters:

metrics - the Metrics class

getDevices

public Device[] getDevices()

Returns the devices used for training.

Returns:

the devices used for training

getLoss

public Loss getLoss()

Gets the training Loss function of the trainer.

Returns:

the Loss function

getModel

public Model getModel()

Returns the model used to create this trainer.

Returns:

the model associated with this trainer

getExecutorService

public java.util.Optional<java.util.concurrent.ExecutorService> getExecutorService()

Returns the ExecutorService.

Returns:

the ExecutorService

getEvaluators

public java.util.List<Evaluator> getEvaluators()

Gets all Evaluators.

Returns:

the evaluators used during training

notifyListeners

public final void notifyListeners(java.util.function.Consumer<TrainingListener> listenerConsumer)

Executes a method on each of the TrainingListeners.

Parameters:

listenerConsumer - a consumer that executes the method

getTrainingResult

public TrainingResult getTrainingResult()

Returns the TrainingResult.

Returns:

the TrainingResult

getManager

public NDManager getManager()

Gets the NDManager from the model.

Returns:

the NDManager

finalize

protected void finalize()
                 throws java.lang.Throwable

Overrides:

finalize in class java.lang.Object

Throws:

java.lang.Throwable

close

public void close()

Specified by:

close in interface java.lang.AutoCloseable

addMetric

public void addMetric(java.lang.String metricName,
                      long begin)

Helper to add a metric for a time difference.

Parameters:

metricName - the metric name

begin - the time difference start (this method is called at the time difference end)