From 5e3eb12a7b78092cd6bc31892b76e5ef976ad462 Mon Sep 17 00:00:00 2001
From: yoshitaka-i <8393063+inoue0426@users.noreply.github.com>
Date: Fri, 13 Mar 2020 16:33:36 +0900
Subject: [PATCH] add relu function (#1795)

---
 maths/relu.py | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 maths/relu.py

diff --git a/maths/relu.py b/maths/relu.py
new file mode 100644
index 000000000..2c41d2e9d
--- /dev/null
+++ b/maths/relu.py
@@ -0,0 +1,39 @@
+"""
+This script demonstrates the implementation of the ReLU function.
+
+It's a kind of activation function defined as the positive part of its argument in the context of neural network.
+The function takes a vector of K real numbers as input and then argmax(x, 0).
+After through ReLU, the element of the vector always 0 or real number.
+
+Script inspired from its corresponding Wikipedia article
+https://en.wikipedia.org/wiki/Rectifier_(neural_networks)
+"""
+
+import numpy as np
+from typing import List
+
+
+def relu(vector: List[float]):
+    """
+        Implements the relu function
+
+        Parameters:
+            vector (np.array,list,tuple): A  numpy array of shape (1,n)
+            consisting of real values or a similar list,tuple
+
+
+        Returns:
+            relu_vec (np.array): The input numpy array, after applying
+            relu.
+
+        >>> vec = np.array([-1, 0, 5])
+        >>> relu(vec)
+        array([0, 0, 5])
+    """
+
+    # compare two arrays and then return element-wise maxima.
+    return np.maximum(0, vector)
+
+
+if __name__ == "__main__":
+    print(np.array(relu([-1, 0, 5])))  # --> [0, 0, 5]