diff --git a/machine_learning/multilayer_perceptron_classifier.py b/machine_learning/multilayer_perceptron_classifier.py index 40f998c7dfa2..548575995c2f 100644 --- a/machine_learning/multilayer_perceptron_classifier.py +++ b/machine_learning/multilayer_perceptron_classifier.py @@ -1,26 +1,99 @@ -from sklearn.neural_network import MLPClassifier +""" +Multilayer Perceptron (MLP) Classifier + +A Multilayer Perceptron (MLP) is a type of feedforward artificial neural network +that consists of at least three layers of nodes: an input layer, one or more hidden +layers, and an output layer. Each node (except for the input nodes) is a neuron +that uses a nonlinear activation function. + +Mathematical Concept: +--------------------- +MLPs learn a function f(·): R^m → R^o by training on a dataset, where m is the +number of input features and o is the number of output classes. The network +adjusts its weights using backpropagation to minimize the difference between +predicted and actual outputs. -X = [[0.0, 0.0], [1.0, 1.0], [1.0, 0.0], [0.0, 1.0]] -y = [0, 1, 0, 0] +Practical Use Cases: +-------------------- +- Handwritten digit recognition (e.g., MNIST dataset) +- Binary and multiclass classification tasks +- Predicting outcomes based on multiple features + (e.g., medical diagnosis, spam detection) +Advantages: +----------- +- Can learn non-linear decision boundaries +- Works well with complex pattern recognition +- Flexible architecture for various problem types -clf = MLPClassifier( - solver="lbfgs", alpha=1e-5, hidden_layer_sizes=(5, 2), random_state=1 -) +Limitations: +------------ +- Requires careful tuning of hyperparameters +- Sensitive to feature scaling +- Can overfit on small datasets -clf.fit(X, y) +Time Complexity: O(n_samples * n_features * n_layers * n_epochs) +Space Complexity: O(n_features * n_hidden_units + n_hidden_units * n_classes) +References: +----------- +- https://en.wikipedia.org/wiki/Multilayer_perceptron +- https://scikit-learn.org/stable/modules/neural_networks_supervised.html +- https://medium.com/@aryanrusia8/multi-layer-perceptrons-explained-7cb9a6e318c3 -test = [[0.0, 0.0], [0.0, 1.0], [1.0, 1.0]] -Y = clf.predict(test) +Example: +-------- +>>> X = [[0, 0], [1, 1], [0, 1], [1, 0]] +>>> y = [0, 0, 1, 1] +>>> result = multilayer_perceptron_classifier(X, y, [[0, 0], [1, 1]]) +>>> result in [[0, 0], [0, 1], [1, 0], [1, 1]] +True +""" + +from collections.abc import Sequence + +from sklearn.neural_network import MLPClassifier -def wrapper(y): +def multilayer_perceptron_classifier( + train_features: Sequence[Sequence[float]], + train_labels: Sequence[int], + test_features: Sequence[Sequence[float]], +) -> list[int]: """ - >>> [int(x) for x in wrapper(Y)] - [0, 0, 1] + Train a Multilayer Perceptron classifier and predict labels for test data. + + Args: + train_features: Training data features, shape (n_samples, n_features). + train_labels: Training data labels, shape (n_samples,). + test_features: Test data features to predict, shape (m_samples, n_features). + + Returns: + List of predicted labels for the test data. + + Raises: + ValueError: If the number of training samples and labels do not match. + + Example: + >>> X = [[0, 0], [1, 1], [0, 1], [1, 0]] + >>> y = [0, 0, 1, 1] + >>> result = multilayer_perceptron_classifier(X, y, [[0, 0], [1, 1]]) + >>> result in [[0, 0], [0, 1], [1, 0], [1, 1]] + True """ - return list(y) + if len(train_features) != len(train_labels): + raise ValueError("Number of training samples and labels must match.") + + clf = MLPClassifier( + solver="lbfgs", + alpha=1e-5, + hidden_layer_sizes=(5, 2), + random_state=42, # Fixed for deterministic results + max_iter=1000, # Ensure convergence + ) + clf.fit(train_features, train_labels) + predictions = clf.predict(test_features) + return list(predictions) if __name__ == "__main__":