From 2d84b6e5a34fd8fbc62a96c4842665701ab4e9bd Mon Sep 17 00:00:00 2001
From: jvech <jmvalenciae@unal.edu.co>
Date: Wed, 2 Aug 2023 15:11:27 -0500
Subject: add: delta calculation for hidden and output layer done

---
 src/nn.c | 35 +++++++++++++++++++++++++++++++++++
 src/nn.h | 23 ++++++++++++++++++++---
 2 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/src/nn.c b/src/nn.c
index 14120a5..6aa7213 100644
--- a/src/nn.c
+++ b/src/nn.c
@@ -2,6 +2,41 @@
 
 static void fill_random_weights(double *weights, double *bias, size_t rows, size_t cols);
 
+void nn_layer_hidden_delta(
+        double *delta, size_t delta_cols,
+        double *delta_next, size_t delta_next_cols,
+        double *weigths_next, size_t weigths_shape[2],
+        double *zout, size_t zout_cols,
+        double (*activation_derivative)(double))
+{
+    assert(delta_cols == zout_cols);
+    assert(delta_cols == weigths_shape[0]);
+    assert(delta_next_cols == weigths_shape[1]);
+
+    for (size_t j = 0; j < delta_cols; j++) {
+        double sum = 0;
+        for (size_t k = 0; k < delta_next_cols; k++) {
+            size_t index = j * delta_cols + k;
+            sum += delta_next[k] * weigths_next[index];
+        }
+        delta[j] = sum * activation_derivative(zout[j]);
+    }
+}
+
+void nn_layer_out_delta(
+        double *delta, size_t delta_cols,
+        double *error, size_t error_cols,
+        double *zout, size_t zout_cols,
+        double (*activation_derivative)(double))
+{
+    assert(delta_cols == error_cols);
+    assert(zout_cols == error_cols);
+
+    for (size_t i = 0; i < delta_cols; i++) {
+        delta[i] = error[i] * activation_derivative(zout[i]);
+    }
+}
+
 void nn_forward(
         double **out, double **zout,
         double *X, size_t X_shape[2],
diff --git a/src/nn.h b/src/nn.h
index 62f438d..d6dd1fe 100644
--- a/src/nn.h
+++ b/src/nn.h
@@ -2,6 +2,7 @@
 #define __NN__
 
 #include <stdlib.h>
+#include <assert.h>
 #include <stdio.h>
 #include <stdint.h>
 #include <string.h>
@@ -18,11 +19,16 @@ typedef struct Layer {
 void nn_network_init_weights(Layer *network, size_t nmemb, size_t input_cols);
 void nn_network_free_weights(Layer *network, size_t nmemb);
 
-void nn_layer_map_activation(double (*activation)(double), double *aout, size_t aout_shape[2], double *zout, size_t zout_shape[2]);
+void nn_layer_map_activation(
+        double (*activation)(double),
+        double *aout, size_t aout_shape[2],
+        double *zout, size_t zout_shape[2]);
+
 void nn_layer_forward(Layer layer, double *out, size_t out_shape[2], double *input, size_t input_shape[2]);
 void nn_layer_backward(
-        Layer *layer,
+        Layer layer,
         double *weights,
+        double *cost_derivative, size_t dcost_shape[2],
         double *out, size_t out_shape[2],
         double *labels, size_t labels_shape[2],
         double *local_gradient); //TODO
@@ -33,5 +39,16 @@ double identity(double x);
 
 
 void nn_forward(double **aout, double **zout, double *input, size_t input_shape[2], Layer network[], size_t network_size);
-double nn_layer_out_delta(double error, double (*activation_derivative)(double));
+void nn_layer_out_delta(
+        double *delta, size_t delta_cols,
+        double *error, size_t error_cols,
+        double *zout, size_t zout_cols,
+        double (*activation_derivative)(double));//TODO
+
+void nn_layer_hidden_delta(
+        double *delta, size_t delta_cols,
+        double *delta_next, size_t delta_next_cols,
+        double *weigths_next, size_t weigths_shape[2],
+        double *zout, size_t zout_cols,
+        double (*activation_derivative)(double));//TODO
 #endif
-- 
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