ai.djl.training.optimizer.Optimizer Maven / Gradle / Ivy
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* Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except in compliance
* with the License. A copy of the License is located at
*
* http://aws.amazon.com/apache2.0/
*
* or in the "license" file accompanying this file. This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES
* OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions
* and limitations under the License.
*/
package ai.djl.training.optimizer;
import ai.djl.Device;
import ai.djl.ndarray.NDArray;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Function;
/**
* An {@code Optimizer} updates the weight parameters to minimize the loss function. {@code
* Optimizer} is an abstract class that provides the base implementation for optimizers.
*
* @see The D2L chapters on
* optimization algorithms
*/
public abstract class Optimizer {
protected float rescaleGrad;
protected float clipGrad;
private float weightDecays;
private int beginNumUpdate;
private int numUpdate;
private Map updateCounts = new ConcurrentHashMap<>();
/**
* Creates a new instance of {@code Optimizer}.
*
* @param builder the builder used to create an instance of {@code Optimizer}
*/
public Optimizer(OptimizerBuilder builder) {
this.rescaleGrad = builder.rescaleGrad;
this.weightDecays = builder.weightDecays;
this.clipGrad = builder.clipGrad;
this.beginNumUpdate = builder.beginNumUpdate;
}
/**
* Returns a new instance of {@link ai.djl.training.optimizer.Sgd.Builder} that can build an
* {@link Sgd} optimizer.
*
* @return the {@link Sgd} {@link ai.djl.training.optimizer.Sgd.Builder}
*/
public static Sgd.Builder sgd() {
return new Sgd.Builder();
}
/**
* Returns a new instance of {@link ai.djl.training.optimizer.Nag.Builder} that can build an
* {@link Nag} optimizer.
*
* @return the {@link Nag} {@link ai.djl.training.optimizer.Nag.Builder}
*/
public static Nag.Builder nag() {
return new Nag.Builder();
}
/**
* Returns a new instance of {@link ai.djl.training.optimizer.Adam.Builder} that can build an
* {@link Adam} optimizer.
*
* @return the {@link Adam} {@link ai.djl.training.optimizer.Adam.Builder}
*/
public static Adam.Builder adam() {
return new Adam.Builder();
}
/**
* Returns a new instance of {@link RmsProp.Builder} that can build an {@link RmsProp}
* optimizer.
*
* @return the {@link RmsProp} {@link RmsProp.Builder}
*/
public static RmsProp.Builder rmsprop() {
return new RmsProp.Builder();
}
/**
* Returns a new instance of {@link ai.djl.training.optimizer.Adagrad.Builder} that can build an
* {@link Adagrad} optimizer.
*
* @return the {@link Adagrad} {@link ai.djl.training.optimizer.Adagrad.Builder}
*/
public static Adagrad.Builder adagrad() {
return new Adagrad.Builder();
}
/**
* Returns a new instance of {@link ai.djl.training.optimizer.Adadelta.Builder} that can build
* an {@link Adadelta} optimizer.
*
* @return the {@link Adadelta} {@link ai.djl.training.optimizer.Adadelta.Builder}
*/
public static Adadelta.Builder adadelta() {
return new Adadelta.Builder();
}
/**
* Gets the value of weight decay.
*
* @return the value of weight decay
*/
protected float getWeightDecay() {
return weightDecays;
}
protected int updateCount(String parameterId) {
// if index exists, increment update count, if not, use begin number of update + 1
int count =
updateCounts.compute(
parameterId, (key, val) -> (val == null) ? beginNumUpdate + 1 : val + 1);
numUpdate = Math.max(numUpdate, count);
return numUpdate;
}
/**
* Updates the parameters according to the gradients.
*
* @param parameterId the parameter to be updated
* @param weight the weights of the parameter
* @param grad the gradients
*/
public abstract void update(String parameterId, NDArray weight, NDArray grad);
protected NDArray withDefaultState(
Map> state,
String key,
Device device,
Function defaultFunction) {
Map arrayMap =
state.computeIfAbsent(
key,
k -> {
Map map = new ConcurrentHashMap<>();
NDArray s = defaultFunction.apply(k);
// TODO attach s to the NDManager of ParameterStore
s.detach(); // s is detached because it would be put into the optimizer
// callback manager and closed after the optimizer callback
// when using the MxParameterServer. For now, this will let it be closed
// by the
// GC when the optimizer is out of scope. Ideally, it should be put into
// the
// trainer manager instead.
map.put(device, s);
return map;
});
return arrayMap.computeIfAbsent(
device, k -> arrayMap.values().iterator().next().toDevice(device, true));
}
/** The Builder to construct an {@link Optimizer}. */
@SuppressWarnings("rawtypes")
public abstract static class OptimizerBuilder {
private float rescaleGrad = 1.0f;
private float weightDecays;
private float clipGrad = -1;
private int beginNumUpdate;
protected OptimizerBuilder() {}
/**
* Sets the value used to rescale the gradient. This is used to alleviate the effect of
* batching on the loss. Usually, the value is set to \( 1/batch_size \). Defaults to 1.
*
* @param rescaleGrad the value used to rescale the gradient
* @return this {@code Builder}
*/
public T setRescaleGrad(float rescaleGrad) {
this.rescaleGrad = rescaleGrad;
return self();
}
/**
* Sets the value of weight decay. Weight decay augments the objective function with a
* regularization term that penalizes large weights.
*
* @param weightDecays the value of weight decay to be set
* @return this {@code Builder}
*/
public T optWeightDecays(float weightDecays) {
this.weightDecays = weightDecays;
return self();
}
/**
* Sets the value of the \(clipGrad\). Clips the gradient to the range of \([-clipGrad,
* clipGrad]\). If \(clipGrad \lt 0\), gradient clipping is turned off.
*
* \(grad = max(min(grad, clipGrad), -clipGrad)\)
*
* @param clipGrad the value of \(clipGrad\)
* @return this {@code Builder}
*/
public T optClipGrad(float clipGrad) {
this.clipGrad = clipGrad;
return self();
}
/**
* Sets the initial value of the number of updates.
*
* @param beginNumUpdate the initial value of the number of updates
* @return this {@code Builder}
*/
public T optBeginNumUpdate(int beginNumUpdate) {
this.beginNumUpdate = beginNumUpdate;
return self();
}
protected abstract T self();
}
}
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