lightning/docs/source-pytorch/clouds/cluster_intermediate_1.rst

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Run on an on-prem cluster (intermediate)
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**Audience**: Users who need to run on an academic or enterprise private cluster.
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.. _non-slurm:
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Setup the cluster
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This guide shows how to run a training job on a general purpose cluster. We recommend beginners to try this method
first because it requires the least amount of configuration and changes to the code.
To setup a multi-node computing cluster you need:
1) Multiple computers with PyTorch Lightning installed
2) A network connectivity between them with firewall rules that allow traffic flow on a specified *MASTER_PORT*.
3) Defined environment variables on each node required for the PyTorch Lightning multi-node distributed training
PyTorch Lightning follows the design of `PyTorch distributed communication package <https://pytorch.org/docs/stable/distributed.html#environment-variable-initialization>`_. and requires the following environment variables to be defined on each node:
- *MASTER_PORT* - required; has to be a free port on machine with NODE_RANK 0
- *MASTER_ADDR* - required (except for NODE_RANK 0); address of NODE_RANK 0 node
- *WORLD_SIZE* - required; how many nodes are in the cluster
- *NODE_RANK* - required; id of the node in the cluster
.. _training_script_setup:
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Setup the training script
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To train a model using multiple nodes, do the following:
1. Design your :ref:`lightning_module` (no need to add anything specific here).
2. Enable DDP in the trainer
.. code-block:: python
# train on 32 GPUs across 4 nodes
trainer = Trainer(accelerator="gpu", devices=8, num_nodes=4, strategy="ddp")
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Submit a job to the cluster
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To submit a training job to the cluster you need to run the same training script on each node of the cluster.
This means that you need to:
1. Copy all third-party libraries to each node (usually means - distribute requirements.txt file and install it).
2. Copy all your import dependencies and the script itself to each node.
3. Run the script on each node.
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Debug on a cluster
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When running in DDP mode, some errors in your code can show up as an NCCL issue.
Set the ``NCCL_DEBUG=INFO`` environment variable to see the ACTUAL error.
.. code-block:: bash
NCCL_DEBUG=INFO python train.py ...
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Get help
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Setting up a cluster for distributed training is not trivial. Lightning offers lightning-grid which allows you to configure a cluster easily and run experiments via the CLI and web UI.
Try it out for free today:
.. raw:: html
<div class="display-card-container">
<div class="row">
.. Add callout items below this line
.. displayitem::
:header: Train models on the cloud
:description: Learn to run a model in the background on a cloud machine.
:col_css: col-md-6
:button_link: cloud_training.html
:height: 150
:tag: intermediate
.. raw:: html
</div>
</div