diff --git a/maths/sigmoid_linear_unit.py b/maths/sigmoid_linear_unit.py new file mode 100644 index 000000000..a8ada10dd --- /dev/null +++ b/maths/sigmoid_linear_unit.py @@ -0,0 +1,57 @@ +""" +This script demonstrates the implementation of the Sigmoid Linear Unit (SiLU) +or swish function. +* https://en.wikipedia.org/wiki/Rectifier_(neural_networks) +* https://en.wikipedia.org/wiki/Swish_function + +The function takes a vector x of K real numbers as input and returns x * sigmoid(x). +Swish is a smooth, non-monotonic function defined as f(x) = x * sigmoid(x). +Extensive experiments shows that Swish consistently matches or outperforms ReLU +on deep networks applied to a variety of challenging domains such as +image classification and machine translation. + +This script is inspired by a corresponding research paper. +* https://arxiv.org/abs/1710.05941 +""" + +import numpy as np + + +def sigmoid(vector: np.array) -> np.array: + """ + Mathematical function sigmoid takes a vector x of K real numbers as input and + returns 1/ (1 + e^-x). + https://en.wikipedia.org/wiki/Sigmoid_function + + >>> sigmoid(np.array([-1.0, 1.0, 2.0])) + array([0.26894142, 0.73105858, 0.88079708]) + """ + return 1 / (1 + np.exp(-vector)) + + +def sigmoid_linear_unit(vector: np.array) -> np.array: + """ + Implements the Sigmoid Linear Unit (SiLU) or swish function + + Parameters: + vector (np.array): A numpy array consisting of real + values. + + Returns: + swish_vec (np.array): The input numpy array, after applying + swish. + + Examples: + >>> sigmoid_linear_unit(np.array([-1.0, 1.0, 2.0])) + array([-0.26894142, 0.73105858, 1.76159416]) + + >>> sigmoid_linear_unit(np.array([-2])) + array([-0.23840584]) + """ + return vector * sigmoid(vector) + + +if __name__ == "__main__": + import doctest + + doctest.testmod()