lightning/docs/source/apex.rst

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16-bit training
=================
Lightning offers 16-bit training for CPUs, GPUs and TPUs.
GPU 16-bit
-----------
Lightning uses NVIDIA apex to handle 16-bit precision training.
To use 16-bit precision, do two things:
1. Install Apex
2. Set the "precision" trainer flag.
Install apex
^^^^^^^^^^^^
.. code-block:: bash
$ git clone https://github.com/NVIDIA/apex
$ cd apex
# ------------------------
# OPTIONAL: on your cluster you might need to load cuda 10 or 9
# depending on how you installed PyTorch
# see available modules
module avail
# load correct cuda before install
module load cuda-10.0
# ------------------------
# make sure you've loaded a cuda version > 4.0 and < 7.0
module load gcc-6.1.0
$ pip install -v --no-cache-dir --global-option="--cpp_ext" --global-option="--cuda_ext" ./
Enable 16-bit
^^^^^^^^^^^^^
.. code-block:: python
# turn on 16-bit
trainer = Trainer(amp_level='O1', precision=16)
If you need to configure the apex init for your particular use case or want to use a different way of doing
16-bit training, override :meth:`pytorch_lightning.core.LightningModule.configure_apex`.
TPU 16-bit
----------
16-bit on TPus is much simpler. To use 16-bit with TPUs set precision to 16 when using the tpu flag
.. code-block:: python
# DEFAULT
trainer = Trainer(num_tpu_cores=8, precision=32)
# turn on 16-bit
trainer = Trainer(num_tpu_cores=8, precision=16)