Refactor size calculations in layers and backend

include/tensor.hpp

@@ -16,6 +16,19 @@ enum class DType
     // INT32,  // Not implemented yet
 };
 
+size_t dtype_size(DType dtype) {
+    switch (dtype)
+    {
+    case DType::FLOAT32:
+        return 4;
+        break;
+    
+    default:
+        throw std::runtime_error("Unknown DType");
+        break;
+    }
+}
+
 class Tensor
 {
 public: