ADD: add SiLU function

nn/functional/nn_silu.c

@@ -0,0 +1,29 @@
+
+#include "nn_silu.h"
+
+
+void NN_silu(Tensor *y, const Tensor *x) {
+  assert(y->ndim == x->ndim);
+  assert(y->dtype == x->dtype);
+  assert(y->size == x->size);
+
+  switch (y->dtype) {
+    case DTYPE_F32:
+      for (size_t i = 0; i < y->size; i++) {
+        float x_i = ((float *)x->data)[i];
+        ((float *)y->data)[i] = x_i / (1.0f + expf(-x_i));
+      }
+      return;
+
+    default:
+      break;
+  }
+
+  printf("[ERROR] Unsupported operation between tensor with dtype %s = SiLU(%s)\n", 
+    NN_get_datatype_name(y->dtype), NN_get_datatype_name(x->dtype)
+  );
+}
+
+void NN_silu_inplace(Tensor *x) {
+  NN_silu(x, x);
+}

nn/functional/nn_silu.h

@@ -0,0 +1,24 @@
+#ifndef __NN_SILU_H
+#define __NN_SILU_H
+
+#include <assert.h>
+
+#include "nn_tensor.h"
+#include "maximum1.h"
+
+
+/**
+ * Applies the Sigmoid Linear Unit (SiLU) function, element-wise.
+ * 
+ * The SiLU function is also known as the swish function.
+ * 
+ * y = silu(x) = x * theta(x), where theta(x) is the logistic sigmoid.
+ * 
+ * @param y: the output tensor
+ * @param x: the input tensor
+ */
+void NN_silu(Tensor *y, const Tensor *x);
+
+void NN_silu_inplace(Tensor *x);
+
+#endif // __NN_SILU_H