Optimization of a custom loss function I want to implement a deep learning model in Keras, but I want to use my own loss function, i.e. custom loss. If I implement some loss function and use Keras Functional API for the model, do I need to change the way the optimizer works, because the optimizer will minimize my loss function? If I need to do that, what is the way to do that?
You don't need to change the way optimizer works. You just need to define your loss function in some standard way. 

Checkout the answer in this post to have an idea on an example of customizing loss function in Keras. 

https://stackoverflow.com/questions/45961428/make-a-custom-loss-function-in-keras