#
Experiment trackers

There are a large number of experiment tracking APIs available, however getting them all to work in a multi-processing environment can oftentimes be complex. Accelerate provides a general tracking API that can be used to log useful items during your script through `Accelerator.log()`

##
Integrated Trackers

Currently `Accelerate` supports eight trackers out-of-the-box:

- TensorBoard
- WandB
- Trackio
- CometML
- Aim
- MLFlow
- ClearML
- DVCLive

To use any of them, pass in the selected type(s) to the `log_with` parameter in `Accelerate`:

    from accelerate import Accelerator
    from accelerate.utils import LoggerType

    accelerator = Accelerator(log_with="all")  # For all available trackers in the environment
    accelerator = Accelerator(log_with="wandb")
    accelerator = Accelerator(log_with=["wandb", LoggerType.TENSORBOARD])

At the start of your experiment `Accelerator.init_trackers()` should be used to setup your project, and potentially add any experiment hyperparameters to be logged:

    hps = {"num_iterations": 5, "learning_rate": 1e-2}
    accelerator.init_trackers("my_project", config=hps)

When you are ready to log any data, `Accelerator.log()` should be used. A `step` can also be passed in to correlate the data with a particular step in the training loop.

    accelerator.log({"train_loss": 1.12, "valid_loss": 0.8}, step=1)

Once you’ve finished training, make sure to run Accelerator.end_training() so that all the trackers can run their finish functionalities if they have any.

    accelerator.end_training()

A full example is below:

    from accelerate import Accelerator

    accelerator = Accelerator(log_with="all")
    config = {
        "num_iterations": 5,
        "learning_rate": 1e-2,
        "loss_function": str(my_loss_function),
    }

    accelerator.init_trackers("example_project", config=config)

    my_model, my_optimizer, my_training_dataloader = accelerator.prepare(my_model, my_optimizer, my_training_dataloader)
    device = accelerator.device
    my_model.to(device)

    for iteration in range(config["num_iterations"]):
        for step, batch in enumerate(my_training_dataloader):
            my_optimizer.zero_grad()
            inputs, targets = batch
            inputs = inputs.to(device)
            targets = targets.to(device)
            outputs = my_model(inputs)
            loss = my_loss_function(outputs, targets)
            accelerator.backward(loss)
            my_optimizer.step()
            accelerator.log({"training_loss": loss}, step=step)
    accelerator.end_training()

If a tracker requires a directory to save data to, such as `TensorBoard`, then pass the directory path to `project_dir`. The `project_dir` parameter is useful when there are other configurations to be combined with in the ProjectConfiguration data class. For example, you can save the TensorBoard data to `project_dir` and everything else can be logged in the `logging_dir` parameter of [`~utils.ProjectConfiguration`:

    accelerator = Accelerator(log_with="tensorboard", project_dir=".")

    # use with ProjectConfiguration
    config = ProjectConfiguration(project_dir=".", logging_dir="another/directory")
    accelerator = Accelerator(log_with="tensorboard", project_config=config)

##
Implementing Custom Trackers

To implement a new tracker to be used in `Accelerator`, a new one can be made through implementing the `GeneralTracker` class. Every tracker must implement three functions and have three properties:

- `__init__`:

  - Should store a `run_name` and initialize the tracker API of the integrated library.
  - If a tracker stores their data locally (such as TensorBoard), a `logging_dir` parameter can be added.

- `store_init_configuration`:

  - Should take in a `values` dictionary and store them as a one-time experiment configuration

- `log`:

  - Should take in a `values` dictionary and a `step`, and should log them to the run

- `name` (`str`):

  - A unique string name for the tracker, such as `"wandb"` for the wandb tracker.
  - This will be used for interacting with this tracker specifically

- `requires_logging_directory` (`bool`):

  - Whether a `logging_dir` is needed for this particular tracker and if it uses one.

- `tracker`:

  - This should be implemented as a `@property` function
  - Should return the internal tracking mechanism the library uses, such as the `run` object for `wandb`.

Each method should also utilize the state.PartialState class if the logger should only be executed on the main process for instance.

A brief example can be seen below with an integration with Weights and Biases, containing only the relevant information and logging just on the main process:

    from accelerate.tracking import GeneralTracker, on_main_process
    from typing import Optional

    import wandb

    class MyCustomTracker(GeneralTracker):
        name = "wandb"
        requires_logging_directory = False

        @on_main_process
        def __init__(self, run_name: str):
            self.run_name = run_name
            run = wandb.init(self.run_name)

        @property
        def tracker(self):
            return self.run.run

        @on_main_process
        def store_init_configuration(self, values: dict):
            wandb.config(values)

        @on_main_process
        def log(self, values: dict, step: Optional[int] = None):
            wandb.log(values, step=step)

When you are ready to build your `Accelerator` object, pass in an instance of your tracker to `Accelerator.log_with` to have it automatically be used with the API:

    tracker = MyCustomTracker("some_run_name")
    accelerator = Accelerator(log_with=tracker)

These also can be mixed with existing trackers, including with `"all"`:

    tracker = MyCustomTracker("some_run_name")
    accelerator = Accelerator(log_with=[tracker, "all"])

##
Accessing the internal tracker

If some custom interactions with a tracker might be wanted directly, you can quickly access one using the Accelerator.get_tracker() method. Just pass in the string corresponding to a tracker’s `.name` attribute and it will return that tracker on the main process.

This example shows doing so with wandb:

    wandb_tracker = accelerator.get_tracker("wandb")

From there you can interact with `wandb`’s `run` object like normal:

    wandb_tracker.log_artifact(some_artifact_to_log)

Trackers built in Accelerate will automatically execute on the correct process, so if a tracker is only meant to be ran on the main process it will do so automatically.

If you want to truly remove Accelerate’s wrapping entirely, you can achieve the same outcome with:

    wandb_tracker = accelerator.get_tracker("wandb", unwrap=True)
    if accelerator.is_main_process:
        wandb_tracker.log_artifact(some_artifact_to_log)

##
When a wrapper cannot work

If a library has an API that does not follow a strict `.log` with an overall dictionary such as Neptune.AI, logging can be done manually under an `if accelerator.is_main_process` statement:

      from accelerate import Accelerator
    + import neptune

      accelerator = Accelerator()
    + run = neptune.init_run(...)

      my_model, my_optimizer, my_training_dataloader = accelerate.prepare(my_model, my_optimizer, my_training_dataloader)
      device = accelerator.device
      my_model.to(device)

      for iteration in config["num_iterations"]:
          for batch in my_training_dataloader:
              my_optimizer.zero_grad()
              inputs, targets = batch
              inputs = inputs.to(device)
              targets = targets.to(device)
              outputs = my_model(inputs)
              loss = my_loss_function(outputs, targets)
              total_loss += loss
              accelerator.backward(loss)
              my_optimizer.step()
    +         if accelerator.is_main_process:
    +             run["logs/training/batch/loss"].log(loss)

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