Gemma model fine-tuning

Fine-tuning a generative artificial intelligence (AI) model such as Gemma modifies the behavior of the model. You typically fine-tune Gemma with the intent of improving its performance on a specific task or domain, or to better fulfill a role, such as customer service. Gemma models are released with open weights, which means you can modify those weights, which then changes the behavior of the model. The general steps for fine-tuning a Gemma model are as follows:

Choose a framework

Gemma models are compatible with a variety of AI tuning frameworks. Each framework offers various advantages and is typically constrained to a specific model format. Here are guides for tuning Gemma models with various frameworks:

Make sure your intended deployment model format, such as Keras format, Safetensors, or GGUF, is supported as an output by your chosen framework.

Collect data

Model tuning requires data. Tuning data typically consists of pairs of input data with the expected response. There are many public datasets available online for training on various tasks or output. For example, if you wanted to train a Gemma model to translate car part descriptions to part numbers, your dataset might include the following:

training_data = [
  {"input_text": "Part number for A4 brake caliper", "output_text": "4M0615107BS"},
  {"input_text": "Part number for Beetle fuel pump", "output_text": "6A127026H"},
  {"input_text": "Part number for Camaro cylinder head", "output_text": "12711770"},
]

If you want a Gemma model to perform a specific set of tasks or role, you typically need to compile a dataset demonstrating multiple variations of that task. How much data you need to tune a model depends on your goals, particularly how much of a behavioral change you want from the model and how well you want the model to perform based on the task to be accomplished and the level of variation in the input data.

In general, you should start with a small set of data for your task tuning, adjust training parameters, and add data until you achieve the task performance that meets your needs. Some of our example applications show that you can influence the behavior of a Gemma model with as few as 20 prompt and response pairs. For more details, see Build a business email AI assistant with Gemma and Tasks in spoken languages with Gemma.

Tune and test the model

Once you have a tuning framework and tuning data in place, you can begin the Gemma model tuning process. When performing tuning, you have some options in how you tune which affects the resources you need to complete it. You also should have a testing plan for your tuned model to evaluate if it is performing the way you want it to after tuning.

Parameter-efficient tuning

When fine-tuning an open weights model such as Gemma, you have the option to tune all the parameters the model or use a less resource intensive parameter efficient tuning technique which updates a subset of them. A full tuning approach means that as you apply your tuning data, you calculate new weights for all parameters of the model. This approach is compute intensive and memory intensive, since you are performing these calculations for billions of parameters. Using less resource intensive tuning approaches, called parameter efficient fine-tuning (PEFT), including techniques like Low Rank Adapter (LoRA) tuning can produce similar results with less compute resources. For details on how to perform tuning with less resources using LoRA, see Fine-tune Gemma models in Keras using LoRA and Fine-Tuning Gemma Models in Hugging Face.

Testing tuned models

Once you have tuned a model for a specific task you should test its performance against the set of tasks you want it to perform. You should test your model with tasks or requests that it was not specifically trained on. How you test your tuned model depends on the task you want it to perform and how closely you manage the inputs and outputs for the model. A common way to manage generative model testing is to use success, failure, and borderline cases:

  • Success tests: Requests that the tuned model should always be able to perform successfully.
  • Failure tests: Requests that the tuned model should always not be able to perform, or explicitly refuse to perform, if requested.
  • Boundary tests: Requests that the tuned model should be able to perform, if they fall within a defined boundary, or set of boundaries, of acceptable output behavior.

When testing failure or boundary conditions for your generative AI application, you should also apply generative AI safety approaches, techniques, and tools as described in the Responsible Generative AI Toolkit.

Deploy the model

After completing your tuning and successful completion of your testing, it's time to deploy your model. You can typically refer to the documentation for your chosen framework for how to deploy a tuned model.

If you are deploying a model with LoRA tuned weights, note that with this technique you typically deploy both the original model and its weights with the LoRA weights as an additional calculation layer for the model.