Package Guide

The AdaptiveResonance.jl package is built upon ART modules that contain all of the state information during training and inference. The ART modules are driven by options, which are themselves mutable keyword argument structs from the Parameters.jl package.

To work with AdaptiveResonance.jl, you should know:

Installation

The AdaptiveResonance package can be installed using the Julia package manager. From the Julia REPL, type ] to enter the Pkg REPL mode and run

julia> ]
(@v.10) pkg> add AdaptiveResonance

Alternatively, it can be added to your environment in a script with

using Pkg
Pkg.add("AdaptiveResonance")

If you wish to have the latest changes between releases, you can directly add the GitHub repo at an arbitrary branch (such as develop) as a dependency with

julia> ]
(@v.10) pkg> add https://github.com/AP6YC/AdaptiveResonance.jl#develop

ART Modules

To work with ART modules, you should know:

Methods

Every ART module is equipped with several constructors, a training function train!, and a classification/inference function classify. ART models are mutable structs, and they can be instantiated with

art = DDVFA()

For more ways to customize instantiation, see the ART options section.

To train and test these models, you use the train! and classify functions upon the models. Because training changes the internal parameters of the ART models and classification does not, train! uses an exclamation point while classify does not, following Julia standard usage.

For example, we may load data of some sort and train/test like so:

# Load the data from some source with a train/test split
train_x, train_y, test_x, test_y = load_some_data()

# Instantiate an arbitrary ART module
art = DDVFA()

# Train the module on the training data, getting the prescribed cluster labels
y_hat_train = train!(art, train_x)

# Conduct inference
y_hat_test = classify(art, test_x)
Note

Because Julia arrays are column-major in memory, the AdaptiveResonance.jl package follows the Julia convention of assuming 2-D data arrays are in the shape of (n_features, n_samples).

Incremental vs. Batch

This training and testing may be done in either incremental or batch modes:

# Create a destination container for the incremental examples
n_train = length(train_y)
n_test = length(test_y)
y_hat_train_incremental = zeros(Integer, n_train)
y_hat_test_incremental = zeros(Integer, n_test)

# Loop over all training samples
for i = 1:n_train
    y_hat_train_incremental[i] = train!(art, train_x[:, i])
end

# loop over all testing samples
for i = 1:n_test
    y_hat_test_incremental[i] = classify(art, test_x[:, i])
end

This is done through checking the dimensionality of the inputs. For example, if a matrix (i.e., 2-D array) is passed to the train! function, then the data is assumed to be (n_features, n_samples), and the module is trained on all samples. However, if the data is a vector (i.e., 1-D array), then the vector is interpreted as a single sample.

When supervised (see supervised vs. unsupervised), the dimensions of the labels must correspond to the dimensions of the data. For example, a 2-D matrix of the data must accompany a 1-D vector of labels, while a 1-D vector of a single data sample must accompany a single integer label.

Batch and incremental modes can be used interchangably after module instantiation.

Note

The first time that an ART module is trained, it infers the data parameters (e.g., feature dimensions, feature ranges, etc.) to setup the internal data configuration. This happens automatically in batch mode, but it cannot happen if the module is only trained incrementally. If you know the dimensions and minimum/maximum values of the features and want to train incrementally, you can use the function data_setup! after module instantiation, which can be used a number of ways. If you have the batch data available, you can set up with

# Manually setup the data config with the data itself
data_setup!(art, data.train_x)

If you do not have the batch data available, you can directly create a DataConfig with the minimums and maximums (inferring the number of features from the lengths of these vectors):

# Get the mins and maxes vectors with some method
mins, maxes = get_some_data_mins_maxes()

# Directly update the data config
art.config = DataConfig(mins, maxes)

If all of the features share the same minimums and maximums, then you can use them as long as you specify the number of features:

# Get the global minimum, maximum, and feature dimension somehow
min, max, dim = get_some_data_characteristics()

# Directly update the data config with these global values
art.config = DataConfig(min, max, dim)

Supervised vs. Unsupervised

ARTMAP modules require a supervised label argument because their formulations typically map internal cluster categories to labels:

# Create an arbitrary ARTMAP module
artmap = DAM()

# Conduct supervised learning
y_hat_train = train!(artmap, train_x, train_y)

# Conduct inference
y_hat_test = classify(artmap, test_x)

In the case of ARTMAP, the returned training labels y_hat_train will always match the training labels train_y by definition. In addition to the classification accuracy (ranging from 0 to 1), you can test that the training labels match with the function performance:

# Verify that the training labels match
perf_train = performance(y_hat_train, train_y)

# Get the classification accuracy
perf_test = performance(y_hat_test, test_y)

However, many ART modules, though unsupervised by definition, can also be trained in a supervised way by naively mapping categories to labels (more in ART vs. ARTMAP).

Mismatch vs. Best-Matching-Unit

During inference, ART algorithms report the category that satisfies the match/vigilance criterion (see Background). By default, in the case that no category satisfies this criterion the module reports a mismatch as -1. In modules that support it, a keyword argument get_bmu (default is false) can be used in the classify method to get the "best-matching unit", which is the category that maximizes the activation. This can be interpreted as the "next-best guess" of the model in the case that the sample is sufficiently different from anything that the model has seen. For example,

# Conduct inference, getting the best-matching unit in case of complete mismatch
y_hat_bmu = classify(my_art, test_x, get_bmu=true)

ART Options

This section contains:

Options Overview

The AdaptiveResonance package is designed for maximum flexibility for scientific research, even though this may come at the cost of learning instability if misused. Because of the diversity of ART modules, the package is structured around instantiating separate modules and using them for training and inference. Due to this diversity, each module has its own options struct with keyword arguments. These options have default values driven by standards in their respective literatures, so the ART modules may be used immediately without any customization. Furthermore, these options are mutable, so they may be modified before module instantiation, before training, or even after training.

For example, you can get going with the default options by creating an ART module with the default constructor:

my_art = DDVFA()

If you want to change the parameters before construction, you can create an options struct, modify it, then instantiate your ART module with it:

my_art_opts = opts_DDVFA()
my_art_opts.gamma = 3
my_art = DDVFA(my_art_opts)

The options are objects from the Parameters.jl project, so they can be instantiated even with keyword arguments:

my_art_opts = opts_DDVFA(gamma = 3)

You can also pass these keyword arguments directly to the ART model when constructing it with

my_art = DDVFA(gamma = 3)

You can even modify the parameters on the fly after the ART module has been instantiated by directly modifying the options within the module:

my_art = DDVFA()
my_art.opts.gamma = 3

Because of the @assert feature of the Parameters.jl package, each parameter is forced to lie within certain bounds by definition in the literature during options instantiation. However, it is possible to change these parameter values beyond their predefined bounds after instantiation.

Note

You must be careful when changing option values during or after training, as it may result in some undefined behavior. Modify the ART module options after instantiation at your own risk and discretion.

ART Options Summary

Though most parameters differ between each ART and ARTMAP module, they all share some quality-of-life options and parameters shared by all ART algorithms:

  • display::Bool: a flag to display or suppress progress bars and logging messages during training and testing.
  • max_epochs::Int: the maximum number of epochs to train over the data, regardless if other stopping conditions have not been met yet.

Otherwise, most ART and ARTMAP modules share the following nomenclature for algorithmic parameters:

  • rho::Float: ART vigilance parameter [0, 1].
  • alpha::Float: Choice parameter > 0.
  • beta::Float: Learning parameter (0, 1].
  • epsilon::Float: Match tracking parameter (0, 1).
  • match::Symbol: A symbolic name of the match function used (i.e., :basic_match). Valid names are listed in MATCH_FUNCTIONS.
  • activation::Symbol: A symbolic name of the activation function used (i.e., :basic_activation). Valid names are listed in ACTIVATION_FUNCTIONS.
  • update::Symbol: A symbolic name of the weight update function used (i.e., :basic_update). Valid names are listed in UPDATE_FUNCTIONS.

ART Activation, Match, and Update Functions

Though their implementations may vary, all ART and ARTMAP modules require the computation of a match function, and activation function, and a method of updating weights when learning. Both ART and ARTMAP modules can now swap out their activation, match, and update functions thanks to Julia's metaprogramming capabilities. This is done by setting the match, activation, or update options of the ART options struct with a symbol of the function to use, such as with

my_opts = opts_FuzzyART(match=:choice_by_difference, activation=:basic_activation, update=:basic_update)

A list of all available activation, match, and update functions is provided in the ACTIVATION_FUNCTIONS, [MATCH_FUNCTIONS], and UPDATE_FUNCTIONS constants, respectively.

ART vs. ARTMAP

ART modules are generally unsupervised in formulation, so they do not explicitly require supervisory labels to their training examples. However, many of these modules can be formulated in the simplified ARTMAP style whereby the ART B module has a vigilance parameter of 1, directly mapping the categories of the ART A module to any provided supervisory labels.

This is done in the training stage through the optional keyword argument y=...:

# Create an arbitrary ART module
art = DDVFA()

# Naively prescribe supervised labels to cluster categories
y_hat_train = train!(art, train_x, y=train_y)

This can also be done incrementally with the same function:

# Get the number of training samples and create a results container
n_train = length(train_y)
y_hat_train_incremental = zeros(Int, n_train)

# Train incrementally over all training samples
for i = 1:n_train
    y_hat_train_incremental[i] = train!(art, train_x[:, i], y=train_y[i])
end

Without provided labels, the ART modules behave as expected, incrementally creating categories when necessary during the training phase.

ART Stats Logging

If you are curious about what the activation and match values were after either incremental training or classifiation, all ART modules implement basic statistics dictionaries in their stats field with the following entries:

  • T: the activation value of the most recent winning node (i.e., the best-matching unit).
  • M: the match value of the most recent winning node.
  • bmu: the integer index of the best-matching unit.
  • mismatch: whether a mismatch occurred during the most recent training/classification iteration.

These fields are useful if you wish to know the degree to which a sample is recognized by your ART module and agrees with its understanding of the data.

For example, you may train a model on some random data (rather inneffectually, but simply for illustration purposes):

# Create a FuzzyART module with default options
my_art = FuzzyART()
# Use three feature dimensions
dim = 3
# Create ten random samples
n_samples = 10
# Create random features and integer labels
features = rand(dim, n_samples)
labels = rand(1:3, n_samples)
# Train the module in simple supervised mode
train!(my_art, features, y=labels)
# See what the activation and match values were for the last sample
T_bmu = my_art.stats["T"]
M_bmu = my_art.stats["M"]
# We can also see which node was the best-matching unit and whether mismatch occured
bmu_index = my_art.stats["bmu"]
mismatch_flag = my_art.stats["mismatch"]