Initializes internal state and build fp32 master copy of weights.

        :param model: fp16 model

def initialize_model(self, model):
        """
        Initializes internal state and build fp32 master copy of weights.

        :param model: fp16 model
        """
        logging.info('Initializing fp32 clone weights')
        self.fp16_model = model
        self.fp16_model.zero_grad()
        self.fp32_params = [param.to(torch.float32).detach()
                            for param in model.parameters()]

        for param in self.fp32_params:
            param.requires_grad = True