[PyTorch] BN Layer Freeze

https://github.com/zhenghao977/FCOS-PyTorch-37.2AP/blob/2bfa4b6ca57358f52f7bc7b44f506608e99894e6/model/fcos.py#L22-L35

GitHub - zhenghao977/FCOS-PyTorch-37.2AP: A pure torch implement of FCOS 37.2AP

        def freeze_bn(module):
            if isinstance(module,nn.BatchNorm2d):
                module.eval()
            classname = module.__class__.__name__
            if classname.find('BatchNorm') != -1:
                for p in module.parameters(): p.requires_grad=False
        if self.config.freeze_bn:
            self.apply(freeze_bn)
            print("INFO===>success frozen BN")