From dbbf5f96170466e91bcd43b2ea22d72524a9b0b4 Mon Sep 17 00:00:00 2001
From: Palash Tyagi <23239946+Magnus167@users.noreply.github.com>
Date: Sun, 6 Jul 2025 17:40:41 +0100
Subject: [PATCH] Add activation functions: sigmoid, dsigmoid, relu, and drelu

---
 src/compute/activations.rs | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 src/compute/activations.rs

diff --git a/src/compute/activations.rs b/src/compute/activations.rs
new file mode 100644
index 0000000..80b9928
--- /dev/null
+++ b/src/compute/activations.rs
@@ -0,0 +1,18 @@
+use crate::matrix::{Matrix, SeriesOps};
+
+pub fn sigmoid(x: &Matrix<f64>) -> Matrix<f64> {
+    x.map(|v| 1.0 / (1.0 + (-v).exp()))
+}
+
+pub fn dsigmoid(y: &Matrix<f64>) -> Matrix<f64> {
+    // derivative w.r.t. pre-activation; takes y = sigmoid(x)
+    y.map(|v| v * (1.0 - v))
+}
+
+pub fn relu(x: &Matrix<f64>) -> Matrix<f64> {
+    x.map(|v| if v > 0.0 { v } else { 0.0 })
+}
+
+pub fn drelu(x: &Matrix<f64>) -> Matrix<f64> {
+    x.map(|v| if v > 0.0 { 1.0 } else { 0.0 })
+}