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Custom model development in Neptune ML

A good way to start custom model development is by following Neptune ML toolkit examples to structure and write your training module. The Neptune ML toolkit also implements modularized graph ML model components in the modelzoo that you can stack and use to create your custom model.

In addition, the toolkit provides utility functions that help you generate the necessary artifacts during model training and model transform. You can import this Python package in your custom implementation. Any functions or modules provided in the toolkit are also available in the Neptune ML training environment.

If your Python module has additional external dependencies, you can include these additional dependencies by creating a requirements.txt file in your module's directory. The packages listed in the requirements.txt file will then be installed before your training script is run.

At a minimum, the Python module that implements your custom model needs to contain the following:

Custom model training script development in Neptune ML

Your custom model training script should be an executable Python script like the Neptune ML toolkit's train.py example. It must accept hyperparameter names and values as command-line arguments. During model training, the hyperparameter names are obtained from the model-hpo-configuration.json file. The hyperparameter values either fall within the valid hyperparameter range if the hyperparameter is tunable, or take the default hyperparameter value if it is not tunable.

Your training script is run on a SageMaker training instance using a syntax like this:

python3 (script entry point) --(1st parameter) (1st value) --(2nd parameter) (2nd value) (...)

For all tasks, the Neptune ML AutoTrainer sends several required parameters to your training script in addition to the hyperparameters that you specify, and your script must be able to handle these additional parameters in order to work properly.

These additional required parameters vary somewhat by task:

Your script should save the model parameters, as well as any other artifacts that will be needed to at the end of training.

You can use Neptune ML toolkit utility functions to determine the location of the processed graph data, the location where the model parameters should be saved, and what GPU devices are available on the training instance. See the train.py sample training script for examples of how to use these utility functions.

Custom model transform script development in Neptune ML

A transform script is needed to take advantage of the Neptune ML incremental workflow for model inference on evolving graphs without retraining the model. Even if all the artifacts necessary for model deployment are generated by the training script, you still need to provide a transform script if you want to generate updated models without retraining the model.

Your custom model transform script should be an executable Python script like the Neptune ML toolkit's transform.py example script. Because this script is invoked during model training with no command line arguments, any command line arguments that the script does accept must have defaults.

The script runs on a SageMaker training instance with a syntax like this:

python3 (your transform script entry point)

Your transform script will need various pieces of information, such as:

These inputs are obtained using Neptune ML utility functions that your script can call. See the toolkit's sample transform.py script for examples of how to do that.

The script should save the node embeddings, node ID mappings, and any other artifacts necessary for model deployment for each task. See the model artifacts documentation for more information about the model artifacts required for different Neptune ML tasks.

Custom model-hpo-configuration.json file in Neptune ML

The model-hpo-configuration.json file defines hyperparameters for your custom model. It is in the same format as the model-hpo-configuration.json file used with the Neptune ML built-in models, and takes precedence over the version that is auto-generated by Neptune ML and uploaded to the location of your processed data.

When you add a new hyperparameter to your model, you must also add an entry for the hyperparameter in this file so that the hyperparameter is passed to your training script.

You must provide a range for a hyperparameter if you want it to be tunable, and set it as a tier-1, tier-2, or tier-3 param. The hyperparameter will be tuned if the total number of training jobs configured allow for tuning hyperparameters in its tier. For a non-tunable parameter, you must provide a default value and add the hyperparameter to the fixed-param section of the file. See the toolkit's sample sample model-hpo-configuration.json file for an example of how to do that.

You must also provide the metric definition that the SageMaker HyperParameter Optimization job will use to evaluate the candidate models trained. To do this, you add an eval_metric JSON object to the model-hpo-configuration.json file like this:

"eval_metric": {
  "tuning_objective": {
      "MetricName": "(metric_name)",
      "Type": "Maximize"
  },
  "metric_definitions": [
    {
      "Name": "(metric_name)",
      "Regex": "(metric regular expression)"
    }
  ]
},

The metric_definitions array in the eval_metric object lists metric definition objects for each metric that you want SageMaker to extract from the training instance. Each metric definition object has a Name key that lets you provide a name for the metric (such as "accuracy", "f1", and so on) The Regex key lets you provide a regular expression string that matches how that particular metric is printed in the training logs. See the SageMaker HyperParameter Tuning page for more details on how to define metrics.

The tuning_objective object in eval_metric then allows you to specify which of the metrics in metric_definitions should be used as the evaluation metric that serves as the objective metric for hyperparameter optimization. The value for the MetricName must match the value of a Name in one of the definitions in metric_definitions. The value for Type should be either "Maximize" or "Minimize" depending on whether the metric should be interpreted as greater-is-better (like "accuracy") or less-is-better (like "mean-squared-error".

Errors in this section of the model-hpo-configuration.json file can result in failures of the Neptune ML model training API job, because the SageMaker HyperParameter Tuning job will not be able to select the best model.

Local testing of your custom model implementation in Neptune ML

You can use the Neptune ML toolkit Conda environment to run your code locally in order to test and validate your model. If you're developing on a Neptune Notebook instance, then this Conda environment will be pre-installed on the Neptune Notebook instance. If you’re developing on a different instance, then you need to follow the local setup instructions in the Neptune ML toolkit.

The Conda environment accurately reproduces the environment where your model will run when you call the model training API. All of the example training scripts and transform scripts allow you to pass a command line --local flag to run the scripts in a local environment for easy debugging. This is a good practice while developing your own model because it allows you to interactively and iteratively test your model implementation. During model training in the Neptune ML production training environment, this parameter is omitted.