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In machine learning, hyperparameter optimization [1] or tuning is the problem of choosing a set of optimal hyperparameters for a learning algorithm. A hyperparameter is a parameter whose value is used to control the learning process, which must be configured before the process starts. [2] [3]
In machine learning, a hyperparameter is a parameter that can be set in order to define any configurable part of a model's learning process. Hyperparameters can be classified as either model hyperparameters (such as the topology and size of a neural network) or algorithm hyperparameters (such as the learning rate and the batch size of an optimizer).
[3] [4] For example, in multilayer perceptrons, the same function is preserved when permuting the nodes of a hidden layer, amounting to permuting weight matrices of the network. This property is known as equivariance to permutation of deep weight spaces. [3] The study seeks hyperparameter optimization.
The performance in relation to hyperparameters (colored lines, better performance = blue) does not influence the choice of trials. Finally, the model with the best performance is selected. In this example, 100 trials were run. Looking at a single hyperparameter, much more different values were tried in contrast to grid search (green lines).
Typically, this is repeated for many different hyperparameters (or even different model types) and the validation set is used to determine the best hyperparameter set (and model type) for this inner training set. After this, a new model is fit on the entire outer training set, using the best set of hyperparameters from the inner cross-validation.
In Bayesian statistics, a hyperparameter is a parameter of a prior distribution; the term is used to distinguish them from parameters of the model for the underlying system under analysis. For example, if one is using a beta distribution to model the distribution of the parameter p of a Bernoulli distribution , then:
English: For both hyperparameters of a model, a discrete set of values to search is defined (here, 10 values). In hyperparameter optimization with grid search, the model is trained using each combination of hyperparameter values (100 trials in this example) and the model performance (colored lines, better performance = blue) is saved.
Firstly, use of a hyperprior allows one to express uncertainty in a hyperparameter: taking a fixed prior is an assumption, varying a hyperparameter of the prior allows one to do sensitivity analysis on this assumption, and taking a distribution on this hyperparameter allows one to express uncertainty in this assumption: "assume that the prior is of this form (this parametric family), but that ...