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Optuna integration guide#

Open in Colab

Custom dashboard displaying metadata logged with Optuna

Optuna is an open source hyperparameter optimization framework to automate hyperparameter search. With the Neptune-Optuna integration, you can:

  • Log and monitor the Optuna hyperparameter sweep live:
    • Values and params for each trial
    • Best values and params for the study
    • Hardware consumption and console logs
    • Interactive plots from the optuna.visualization module
    • Parameter distributions for each trial
    • The Study object itself, for "InMemoryStorage" or the database location for the studies with database storage
  • Load the study directly from an existing Neptune run

See example in Neptune  Code examples 

Before you start#

Installing the integration#

To use your preinstalled version of Neptune together with the integration:

pip install -U neptune-optuna
conda install -c conda-forge neptune-optuna

To install both Neptune and the integration:

pip install -U "neptune[optuna]"
conda install -c conda-forge neptune neptune-optuna
Passing your Neptune credentials

Once you've registered and created a project, set your Neptune API token and full project name to the NEPTUNE_API_TOKEN and NEPTUNE_PROJECT environment variables, respectively.

export NEPTUNE_API_TOKEN="h0dHBzOi8aHR0cHM.4kl0jvYh3Kb8...6Lc"

To find your API token: In the bottom-left corner of the Neptune app, expand the user menu and select Get my API token.

export NEPTUNE_PROJECT="ml-team/classification"

Your full project name has the form workspace-name/project-name. You can copy it from the project settings: Click the menu in the top-right → Edit project details.

On Windows, navigate to SettingsEdit the system environment variables, or enter the following in Command Prompt: setx SOME_NEPTUNE_VARIABLE 'some-value'

While it's not recommended especially for the API token, you can also pass your credentials in the code when initializing Neptune.

run = neptune.init_run(
    project="ml-team/classification",  # your full project name here
    api_token="h0dHBzOi8aHR0cHM6Lkc78ghs74kl0jvYh...3Kb8",  # your API token here

For more help, see Set Neptune credentials.

If you'd rather follow the guide without any setup, you can run the example in Colab .

Optuna logging example#

This example shows how to use NeptuneCallback to log Optuna visualizations, Study objects, and other metadata.

For how to customize the NeptuneCallback, see the More options section.

  1. Define your objective, for example:

    import lightgbm as lgb
    import optuna
    from sklearn.datasets import load_breast_cancer
    from sklearn.metrics import roc_auc_score
    from sklearn.model_selection import train_test_split
    def objective(trial):
        data, target = load_breast_cancer(return_X_y=True)
        train_x, test_x, train_y, test_y = train_test_split(
            data, target, test_size=0.25
        dtrain = lgb.Dataset(train_x, label=train_y)
        param = {
            "verbose": -1,
            "objective": "binary",
            "metric": "binary_logloss",
            "num_leaves": trial.suggest_int("num_leaves", 2, 256),
            "feature_fraction": trial.suggest_float(
                "feature_fraction", 0.2, 1.0, step=0.1
            "bagging_fraction": trial.suggest_float(
                "bagging_fraction", 0.2, 1.0, step=0.1
            "min_child_samples": trial.suggest_int("min_child_samples", 3, 100),
        gbm = lgb.train(param, dtrain)
        preds = gbm.predict(test_x)
        return roc_auc_score(test_y, preds)
  2. Import Neptune and create a run:

    import neptune
    run = neptune.init_run() # (1)!
    1. If you haven't set up your credentials, you can log anonymously:

  3. Initialize the Neptune callback:

    import neptune.integrations.optuna as npt_utils
    neptune_callback = npt_utils.NeptuneCallback(run)

    By default, the callback logs all the plots from the optuna.visualization module and the Study object itself after every trial. For how to customize the NeptuneCallback further, see More options.

  4. Run the Optuna parameter sweep with the callback.

    Pass the callback to study.optimize():

    study = optuna.create_study(direction="maximize")
    study.optimize(objective, n_trials=100, callbacks=[neptune_callback])

    Now, when you run your hyperparameter sweep, all the metadata will be logged to Neptune.

  5. To stop the connection to Neptune and sync all data, call the stop() method:

  6. To watch the optimization live, view the run in the Neptune app.

    To open the run, click the Neptune link that appears in the console output.

    Sample output

    [neptune] [info ] Neptune initialized. Open in the app:

    In the above example, the run ID is RUN-1.

Analyzing results in Neptune#

In the Runs section, you can see all your logged runs as a table.

Click on a run to inspect the logged metadata.

Viewing the visualizations#

The visualizations are logged as HTML objects. You can view them in All metadatavisualizations.

To display the visualizations according to your liking, create a custom dashboard and add widgets for fields in the visualizations namespace.

See example dashboard in Neptune 

Filtering the runs by study or trial#

In the runs table, you can filter the runs by level (trial or study) with the help of the tags applied to the runs. This way you can compare trials individually or get the high-level picture of the sweep.

To filter the runs by tag:

  1. In the search box above the table, start typing "tags" to find the sys/tags field.
  2. Choose the condition for the tags.

    For example, to see study-level tags, set the query to Tags + all of + study-level.

  3. Select Done.

You can also use these filters to find all the runs that belong to the sweep-id of the parameter sweep and select them for comparison.

Grouping runs by sweep#

To find your current sweep or compare sweeps between each other, use the group-by function:

  1. Next to the search input box, click Group by.
  2. Enter the name of the field to group the runs by.

    For example, to group by sweep ID, type and select the "sweep-id" field.

  3. To see all trials of a group in a separate table view, click Show all.

More options#

Customizing which plots to log and how often#

By default, NeptuneCallback creates and logs all of the plots from the optuna.visualizations module. This can add overhead to your Optuna sweep, as creating those visualizations takes time.

You can customize which plots you create and log and how often that happens with the following arguments:

  • plot_update_freq:
    • Pass an integer k to update plots every k trials.
    • Pass never to not log any plots.
  • log_plot_contour, log_plot_slice, and other log_{OPTUNA_PLOT_FUNCTION}: If you pass False, the plots will not be created or logged.
objective = ...
run = ...

# Create a Neptune callback for Optuna
neptune_callback = npt_utils.NeptuneCallback(
    plots_update_freq=10,  # create/log plots every 10 trials
    log_plot_slice=False,  # do not create/log plot_slice
    log_plot_contour=False,  # do not create/log plot_contour

# Pass the callback to the optimize() method
study = optuna.create_study(direction="maximize")

# Stop logging to the run

Disabling logging of all trials#

If you want to disable logging of all trials, you can pass


to either the NeptuneCallback() constructor or the log_study_metadata() function.

Logging charts and study object after sweep#

After your sweep has finished, you can log all metadata from your Optuna study with log_study_metadata().

The log_study_metadata() function logs the same metadata that NeptuneCallback logs, and you can customize it with similar flags.

objective = ...
run = ...

# Run Optuna with Neptune callback
study = optuna.create_study(direction="maximize")
study.optimize(objective, n_trials=10)

# Log Optuna charts and study object after the sweep is complete
    target_names=["FLOPS", "accuracy"],  # (optional) one or more study objectives

# Stop logging

Loading the study from existing Neptune run#

If you've logged a Optuna study to Neptune, you can load the study directly from the Neptune run with the load_study_from_run() function and continue working with it.

# Initialize an existing Neptune run
run = neptune.init_run(
    with_id="NEP1-18517",  # The run ID goes here

# Load Optuna study from the Neptune Run
study = npt_utils.load_study_from_run(run)

# Continue logging to the same run
study.optimize(objective, n_trials=10)
How do I find the ID?

The Neptune ID is a unique identifier for the run. In the table view, it's displayed in the leftmost column.

The ID is stored in the system namespace (sys/id).

If the run is active, you can obtain its ID with run["sys/id"].fetch(). For example:

>>> run = neptune.init_run(project="ml-team/classification")
>>> run["sys/id"].fetch()

You can log and load an Optuna study both for InMemoryStorage and database storage.

Logging each trial as separate Neptune run#

You can log trial-level metadata, such as learning curves or diagnostic charts, to a separate run for each trial.

To find and explore all the runs for the hyperparameter sweep later, you can create a study-level run as well as trial-level runs inside of the objective function, then connect these with a custom ID.

  1. Create a unique sweep ID:

    import uuid
    sweep_id = uuid.uuid1()
    print("sweep-id: ", sweep_id)
  2. Create a study-level Neptune run:

    run_study_level = neptune.init_run() # (1)!
    1. If you haven't set up your credentials, you can log anonymously:

  3. Log the sweep ID to the study-level run:

    run_study_level["sweep-id"] = str(sweep_id)

    Add a "study-level" tag to distinguish between the study-level and trial-level runs for the sweep.

  4. Create an objective function that logs each trial to Neptune as a run.

    Inside of the objective function, you need to:

    • Create a trial-level Neptune run
    • Log the sweep ID and a "trial-level" tag to distinguish between the study-level and trial-level runs
    • Log parameters and scores to the trial-level run
    • Stop the trial-level run
    def objective_with_logging(trial):
        param = {
            "num_leaves": trial.suggest_int("num_leaves", 2, 256),
            "feature_fraction": trial.suggest_float("feature_fraction", 0.2, 1.0, step=0.1),
            "bagging_fraction": trial.suggest_float("bagging_fraction", 0.2, 1.0, step=0.1),
            "min_child_samples": trial.suggest_int("min_child_samples", 3, 100),
        # Create a trial-level run
        run_trial_level = neptune.init_run() # (1)!
        # Log sweep ID to trial-level run
        run_trial_level["sweep-id"] = str(sweep_id)
        # Log parameters of a trial-level run
        run_trial_level["parameters"] = param
        # Run training and calculate the score for this parameter configuration
        score = ...
        # Log score of a trial-level Run
        run_trial_level["score"] = score
        # Stop trial-level Run
        return score
    1. If you haven't set up your credentials, you can log anonymously:


    The sweep will take longer, as each trial-level run is stopped inside of the objective function and needs to finish logging metadata to Neptune before the next trial starts.

  5. Create a study-level Neptune callback:

    neptune_callback = npt_utils.NeptuneCallback(run_study_level)
  6. Pass the callback to the study.optimize() method and run the parameter sweep:

    study = optuna.create_study(direction="maximize")
  7. To stop the connection and synchronize the data, call the stop() method:


Navigate to the Neptune app to see your parameter sweep.

  • All sweep runs have the same value in the "sweep-id" field
  • All the trial-level runs are tagged with trial-level
  • The study-level run is tagged with study-level

To compare sweeps between each other, or find your current sweep, group the runs by sweep ID:

  1. Next to the search input box, click Group by.
  2. Type "sweep-id" and select the field.
  3. To open a certain group in a new view, click Show all.

Logging distributed hyperparameter sweeps to single run#

You can log metadata from a distributed Optuna study to a single Neptune run by making use of the custom_run_id parameter.

  1. Create Optuna storage.

    On the command line or in a terminal app, such as Command Prompt:

    optuna create-study \
        --study-name "distributed-example" \
        --storage "mysql://root@localhost/example"

    For more information about distributed hyperparameter sweeps, see the Optuna documentation .

  2. Create a Neptune run with a custom sweep ID.

    Create an ID of a sweep and pass it to custom_run_id:

    run = neptune.init_run(
        custom_run_id="your sweep ID",  # Pass an ID of your sweep


    If your setup allows passing environment variables to worker nodes, you should:

    1. Pass the NEPTUNE_CUSTOM_RUN_ID environment variable to the computational node:

      export NEPTUNE_CUSTOM_RUN_ID = 'your sweep ID'
    2. Then create a Neptune run without specifying the custom_run_id (as it will be picked up from the environment):

    run = neptune.init_run()
  3. Create a Neptune callback and pass it to a loaded Optuna study:

    objective = ...
    run = ...
    neptune_callback = npt_utils.NeptuneCallback(run)
    if __name__ == "__main__":
        study = optuna.load_study(
        study.optimize(objective, n_trials=100, callbacks=[neptune_callback])
  4. Run the distributed study from multiple nodes or processes:

    Process 1


    Process 2

  5. View the distributed Optuna study in Neptune.

Navigate to the Neptune app to see all trials from the distributed Optuna study, logged to a single Neptune run. The custom run ID (stored in the system namespace, sys/custom_run_id) is the sweep ID you chose.

Logging multiple study objectives#

To log one or more study objectives, you can pass a list of objective names to the target_names argument of NeptuneCallback:

neptune_callback = npt_utils.NeptuneCallback(
    run,  # existing Neptune run
    target_names=["FLOPS", "accuracy"],

Then log the multi-objective study metadata to Neptune by passing the callback to the Optuna study:

study = optuna.create_study(directions=["minimize", "maximize"])
study.optimize(objective, n_trials=5, callbacks=[neptune_callback])


You can also pass the target_names to the log_study_metadata() function. See Log charts and study object after sweep.

Manually logging metadata#

If you have other types of metadata that are not covered in this guide, you can still log them using the Neptune client library.

When you initialize the run, you get a run object, to which you can assign different types of metadata in a structure of your own choosing.

import neptune

# Create a new Neptune run
run = neptune.init_run()

# Log metrics inside loops
for epoch in range(n_epochs):
    # Your training loop

    run["train/epoch/loss"].append(loss)  # Each append() call appends a value

# Track artifact versions and metadata

# Upload entire files

# Log text or other metadata, in a structure of your choosing
run["tokenizer"] = "regexp_tokenize"