add: delta calculation for hidden and output layer done

1 files changed, 35 insertions, 0 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],