From bb50c7ea2c5d9e3c294f37670319265e6f5eb7ef Mon Sep 17 00:00:00 2001
From: Al <albarrentine@gmail.com>
Date: Mon, 31 Aug 2015 20:27:58 -0400
Subject: [PATCH] [math] Adding sigmoid and softmax functions

---
 src/logistic.c | 36 ++++++++++++++++++++++++++++++++++++
 src/logistic.h | 14 ++++++++++++++
 2 files changed, 50 insertions(+)
 create mode 100644 src/logistic.c
 create mode 100644 src/logistic.h

diff --git a/src/logistic.c b/src/logistic.c
new file mode 100644
index 00000000..223b15bc
--- /dev/null
+++ b/src/logistic.c
@@ -0,0 +1,36 @@
+#include "logistic.h"
+#include "vector_math.h"
+
+inline double sigmoid(double x) {
+    return 1.0/(1.0 + exp(-x));
+}
+
+inline void sigmoid_vector(double *x, size_t n) {
+    for (int i = 0; i < n; i++) {
+        x[i] = sigmoid(x[i]);
+    }
+}
+
+inline void softmax_vector(double *x, size_t n) {
+    int i;
+    double sum = 0.0;
+    
+    double denom = double_array_log_sum_exp(x, n);
+
+    for (i = 0; i < n; i++) {
+        x[i] = exp(x[i] - denom);
+    }
+}
+
+
+void softmax_matrix(matrix_t *matrix) {
+    size_t num_rows = matrix->m;
+    size_t num_cols = matrix->n;
+
+    double *values = matrix->values;
+
+    for (int i = 0; i < num_rows; i++) {
+        softmax_vector(values, num_cols);
+        values += num_cols;
+    }
+}
\ No newline at end of file
diff --git a/src/logistic.h b/src/logistic.h
new file mode 100644
index 00000000..ddb7de16
--- /dev/null
+++ b/src/logistic.h
@@ -0,0 +1,14 @@
+#ifndef LOGISTIC_H
+#define LOGISTIC_H
+
+#include <stdlib.h>
+#include <stdint.h>
+
+#include "matrix.h"
+
+double sigmoid(double x);
+void sigmoid_vector(double *x, size_t n);
+void softmax_vector(double *x, size_t n);
+void softmax_matrix(matrix_t *matrix);
+
+#endif
\ No newline at end of file