fp16_optimizer.py contains `FP16_Optimizer`, a Python class designed to wrap an existing Pytorch optimizer and automatically enable master parameters and loss scaling in a manner transparent to the user.  To use `FP16_Optimizer`, only two lines of one's Python model need to change.

### [FP16_Optimizer API documentation](https://nvidia.github.io/apex/fp16_utils.html#automatic-management-of-master-params-loss-scaling)

[Simple examples with FP16_Optimizer](https://github.com/NVIDIA/apex/tree/master/examples/FP16_Optimizer_simple)

[Imagenet with FP16_Optimizer](https://github.com/NVIDIA/apex/tree/master/examples/imagenet)

[word_language_model with FP16_Optimizer](https://github.com/NVIDIA/apex/tree/master/examples/word_language_model)


fp16_util.py contains a number of utilities to manually manage master parameters and loss scaling, if the user chooses.  
### [Manual management documentation](https://nvidia.github.io/apex/fp16_utils.html#manual-master-parameter-management)

In addition to `FP16_Optimizer` examples, the Imagenet and word_language_model directories contain examples that demonstrate manual management of master parameters and static loss scaling.  
These examples illustrate what sort of operations `FP16_Optimizer` is performing automatically.