clearml-docs/docs/guides/distributed/distributed_pytorch_example.md
2021-05-19 01:31:01 +03:00

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---
title: PyTorch Distributed
---
The [pytorch_distributed_example.py](https://github.com/allegroai/clearml/blob/master/examples/frameworks/pytorch/pytorch_distributed_example.py)
script demonstrates integrating **ClearML** into code that uses the [PyTorch Distributed Communications Package](https://pytorch.org/docs/stable/distributed.html)
(`torch.distributed`).
The script initializes a main Task and spawns subprocesses, each for an instance of that Task.
The Task in each subprocess trains a neural network over a partitioned dataset (the torchvision built-in [MNIST](https://pytorch.org/vision/stable/datasets.html#mnist)
dataset), and reports (uploads) the following to the main Task:
* Artifacts - A dictionary containing different key-value pairs.
* Scalars - Loss reported as a scalar during training in each Task in a subprocess.
* Hyperparameters - Hyperparameters created in each Task are added to the hyperparameters in the main Task.
Each Task in a subprocess references the main Task by calling [Task.current_task](../../references/sdk/task#taskcurrent_task), which always returns
the main Task.
When the script runs, it creates an experiment named `test torch distributed`, which is associated with the `examples` project
in the **ClearML Web UI**.
## Artifacts
The example uploads a dictionary as an artifact in the main Task by calling the [Task.upload_artifact](../../references/sdk/task.md#upload_artifact)
method on [`Task.current_task`](../../references/sdk/task.md#taskcurrent_task) (the main Task). The dictionary contains the [`dist.rank`](https://pytorch.org/docs/stable/distributed.html#torch.distributed.get_rank)
of the subprocess, making each unique.
Task.current_task().upload_artifact(
'temp {:02d}'.format(dist.get_rank()), artifact_object={'worker_rank': dist.get_rank()})
All of these artifacts appear in the main Task under **ARTIFACTS** **>** **OTHER**.
![image](../../img/examples_pytorch_distributed_example_09.png)
## Scalars
Loss is reported to the main Task by calling the [Logger.report_scalar](../../references/sdk/logger#report_scalar)
method on `Task.current_task().get_logger`, which is the logger for the main Task. Since `Logger.report_scalar` is called
with the same title (`loss`), but a different series name (containing the subprocess' `rank`), all loss scalar series are
logged together.
Task.current_task().get_logger().report_scalar(
'loss', 'worker {:02d}'.format(dist.get_rank()), value=loss.item(), iteration=i)
The single scalar plot for loss appears in **RESULTS** **>** **SCALARS**.
![image](../../img/examples_pytorch_distributed_example_08.png)
## Hyperparameters
**ClearML** automatically logs the argparse command line options. Since the [Task.connect](../../references/sdk/task#connect)
method is called on `Task.current_task`, they are logged in the main Task. A different hyperparameter key is used in each
subprocess, so they do not overwrite each other in the main Task.
param = {'worker_{}_stuff'.format(dist.get_rank()): 'some stuff ' + str(randint(0, 100))}
Task.current_task().connect(param)
All the hyperparameters appear in **CONFIGURATIONS** **>** **HYPER PARAMETERS**.
![image](../../img/examples_pytorch_distributed_example_01.png)
![image](../../img/examples_pytorch_distributed_example_01a.png)
## Console
Output to the console, including the text messages printed from the main Task object and each subprocess appear in **RESULTS** **>** **CONSOLE**.
![image](../../img/examples_pytorch_distributed_example_06.png)