/// <summary>
///
/// </summary>
/// <param name="parameters"></param>
/// <param name="learningRate">A learning rate in float, or a learning rate schedule</param>
/// <param name="gamma">Trade-off factor for current and previous gradients. Common value is 0.95. Should be in range (0.0, 1.0)</param>
/// <param name="inc">Increasing factor when trying to adjust current learning_rate. Should be greater than 1</param>
/// <param name="dec">Decreasing factor when trying to adjust current learning_rate. Should be in range (0.0, 1.0)</param>
/// <param name="max">Maximum scale allowed for the initial learning_rate. Should be greater than zero and min</param>
/// <param name="min">Minimum scale allowed for the initial learning_rate. Should be greater than zero</param>
/// <param name="l1Regularization">L1 regularization term. (Default is 0, so no regularization)</param>
/// <param name="l2Regularization">L2 regularization term. (Default is 0, so no regularization)</param>
/// <param name="gradientClippingThresholdPerSample">clipping threshold per sample, defaults to infinity. (Default is infinity, so no clipping)</param>
/// <param name="gradientClippingWithTruncation">clipping threshold per sample, defaults to infinity. (Default is true)</param>
/// <param name="needAveMultiplier"></param>
/// <returns></returns>
public static Learner RMSProp(IList <Parameter> parameters,
double learningRate = 0.001,
double gamma = 0.9,
double inc = 2.0,
double dec = 0.5,
double max = 2.0,
double min = 0.5,
double l1Regularization = 0.0,
double l2Regularization = 0.0,
double gradientClippingThresholdPerSample = double.PositiveInfinity,
bool gradientClippingWithTruncation = true,
bool needAveMultiplier = true)
{
var learningRatePerSample = new TrainingParameterScheduleDouble(learningRate, 1);
var options = SetAdditionalOptions(l1Regularization,
l2Regularization,
gradientClippingThresholdPerSample,
gradientClippingWithTruncation);
return(CNTKLib.RMSPropLearner(CntkUtilities.CreateParameterVector(parameters),
learningRatePerSample,
gamma, inc, dec, max, min,
needAveMultiplier, options));
}
/// <summary>
/// Stochastic Gradient Descent.
/// </summary>
/// <param name="parameters">Learnable parameters of the model</param>
/// <param name="learningRate">Learning rate. (Default is 0.001)</param>
/// <param name="l1Regularization">L1 regularization term. (Default is 0, so no regularization)</param>
/// <param name="l2Regularization">L2 regularization term. (Default is 0, so no regularization)</param>
/// <param name="gradientClippingThresholdPerSample">clipping threshold per sample, defaults to infinity. (Default is infinity, so no clipping)</param>
/// <param name="gradientClippingWithTruncation">clipping threshold per sample, defaults to infinity. (Default is true)</param>
/// <returns></returns>
public static Learner SGD(IList <Parameter> parameters,
double learningRate = 0.01,
double l1Regularization = 0.0,
double l2Regularization = 0.0,
double gradientClippingThresholdPerSample = double.PositiveInfinity,
bool gradientClippingWithTruncation = true)
{
if (parameters == null)
{
throw new ArgumentNullException("parameters");
}
if (learningRate < 0.0)
{
throw new ArgumentException(nameof(learningRate) + " Has to be larger or equal to 0");
}
if (l1Regularization < 0.0)
{
throw new ArgumentException(nameof(l1Regularization) + " Has to be larger or equal to 0");
}
if (l2Regularization < 0.0)
{
throw new ArgumentException(nameof(l2Regularization) + " Has to be larger or equal to 0");
}
var learningRatePerSample = new TrainingParameterScheduleDouble(learningRate, 1);
var options = SetAdditionalOptions(l1Regularization,
l2Regularization,
gradientClippingThresholdPerSample,
gradientClippingWithTruncation);
return(CNTKLib.SGDLearner(CntkUtilities.CreateParameterVector(parameters),
learningRatePerSample, options));
}
/// <summary>
/// Adam (Adaptive Moment Estimation) is another method that computes adaptive learning rates for each parameter.
/// In addition to storing an exponentially decaying average of past squared gradients vtvt like Adadelta,
/// Adam also keeps an exponentially decaying average of past gradients, similar to momentum.
/// Essentially Adam is RMSProp with momentum.
/// https://arxiv.org/pdf/1412.6980.pdf.
/// </summary>
/// <param name="parameters">Learnable parameters of the model</param>
/// <param name="learningRate">Learning rate. (Default is 0.001)</param>
/// <param name="momentum">Momentum (default is 0.9).
/// Note that this is the beta1 parameter in the Adam paper.</param>
/// <param name="varianceMomentum">variance momentum schedule. (Default is 0.999).
/// Note that this is the beta2 parameter in the Adam paper.</param>
/// <param name="l1Regularization">L1 regularization term. (Default is 0, so no regularization)</param>
/// <param name="l2Regularization">L2 regularization term. (Default is 0, so no regularization)</param>
/// <param name="gradientClippingThresholdPerSample">clipping threshold per sample, defaults to infinity. (Default is infinity, so no clipping)</param>
/// <param name="gradientClippingWithTruncation">clipping threshold per sample, defaults to infinity. (Default is true)</param>
/// <param name="unitGain"></param>
/// <param name="epsilon"></param>
/// <returns></returns>
public static Learner Adam(IList <Parameter> parameters, double learningRate = 0.001,
double momentum = 0.9, double varianceMomentum = 0.999,
double l1Regularization = 0.0,
double l2Regularization = 0.0,
double gradientClippingThresholdPerSample = double.PositiveInfinity,
bool gradientClippingWithTruncation = true,
bool unitGain = true,
double epsilon = 1e-08f)
{
var learningRatePerSample = new TrainingParameterScheduleDouble(learningRate, 1);
var momentumRate = new TrainingParameterScheduleDouble(momentum, 1);
var varianceMomentumRate = new TrainingParameterScheduleDouble(varianceMomentum, 1);
var options = SetAdditionalOptions(l1Regularization,
l2Regularization,
gradientClippingThresholdPerSample,
gradientClippingWithTruncation);
return(CNTKLib.AdamLearner(CntkUtilities.CreateParameterVector(parameters),
learningRatePerSample,
momentumRate,
unitGain,
varianceMomentumRate,
epsilon,
false,
options));
}
/// <summary>
/// Stochastic Gradient Descent with momentum.
/// </summary>
/// <param name="parameters">Learnable parameters of the model</param>
/// <param name="learningRate">Learning rate. (Default is 0.001)</param>
/// <param name="momentum">Momentum (default is 0.9).</param>
/// <param name="l1Regularization">L1 regularization term. (Default is 0, so no regularization)</param>
/// <param name="l2Regularization">L2 regularization term. (Default is 0, so no regularization)</param>
/// <param name="gradientClippingThresholdPerSample">clipping threshold per sample, defaults to infinity. (Default is infinity, so no clipping)</param>
/// <param name="gradientClippingWithTruncation">clipping threshold per sample, defaults to infinity. (Default is true)</param>
/// <param name="unitGain"></param>
/// <returns></returns>
public static Learner MomentumSGD(IList <Parameter> parameters,
double learningRate = 0.01, double momentum = 0.1,
double l1Regularization = 0.0,
double l2Regularization = 0.0,
double gradientClippingThresholdPerSample = double.PositiveInfinity,
bool gradientClippingWithTruncation = true,
bool unitGain = true)
{
var learningRatePerSample = new TrainingParameterScheduleDouble(learningRate, 1);
var momentumPerSample = new TrainingParameterScheduleDouble(momentum, 1);
var options = SetAdditionalOptions(l1Regularization,
l2Regularization,
gradientClippingThresholdPerSample,
gradientClippingWithTruncation);
return(CNTKLib.MomentumSGDLearner(CntkUtilities.CreateParameterVector(parameters),
learningRatePerSample, momentumPerSample, unitGain,
options));
}