added interface to register loss from outside library

Author: WeiPhil

include/tiny-cuda-nn/loss.h

@@ -70,4 +70,7 @@ std::unique_ptr<Loss<T>> default_loss(const std::string& name) {
 
 std::vector<std::string> builtin_losses();
 
+template <typename T>
+void register_loss(const std::string& name, const std::function<Loss<T>*(const json&)>& factory);
+
 }

src/loss.cu

@@ -78,6 +78,9 @@ void register_loss(const std::string& name, const std::function<Loss<T>*(const j
 	register_loss(loss_factories<T>(), name, factory);
 }
 
+template void register_loss<float>(const std::string& name, const std::function<Loss<float>*(const json&)>& factory);
+template void register_loss<__half>(const std::string& name, const std::function<Loss<__half>*(const json&)>& factory);
+
 template <typename T>
 Loss<T>* create_loss(const json& loss) {
 	std::string name = loss.value("otype", "RelativeL2");