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* docs Signed-off-by: Ettore Di Giacinto <mudler@localai.io> * Small enhancements Signed-off-by: Ettore Di Giacinto <mudler@localai.io> * Enhancements * Default to zen-dark Signed-off-by: Ettore Di Giacinto <mudler@localai.io> * fixups Signed-off-by: Ettore Di Giacinto <mudler@localai.io> --------- Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
72 lines
3.3 KiB
Markdown
72 lines
3.3 KiB
Markdown
+++
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disableToc = false
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title = "✍️ Constrained Grammars"
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weight = 15
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url = "/features/constrained_grammars/"
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+++
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## Overview
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The `chat` endpoint supports the `grammar` parameter, which allows users to specify a grammar in Backus-Naur Form (BNF). This feature enables the Large Language Model (LLM) to generate outputs adhering to a user-defined schema, such as `JSON`, `YAML`, or any other format that can be defined using BNF. For more details about BNF, see [Backus-Naur Form on Wikipedia](https://en.wikipedia.org/wiki/Backus%E2%80%93Naur_form).
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{{% notice note %}}
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**Compatibility Notice:** This feature is only supported by models that use the [llama.cpp](https://github.com/ggerganov/llama.cpp) backend. For a complete list of compatible models, refer to the [Model Compatibility]({{%relref "reference/compatibility-table" %}}) page. For technical details, see the related pull requests: [PR #1773](https://github.com/ggerganov/llama.cpp/pull/1773) and [PR #1887](https://github.com/ggerganov/llama.cpp/pull/1887).
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{{% /notice %}}
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## Setup
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To use this feature, follow the installation and setup instructions on the [LocalAI Functions]({{%relref "features/openai-functions" %}}) page. Ensure that your local setup meets all the prerequisites specified for the llama.cpp backend.
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## 💡 Usage Example
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The following example demonstrates how to use the `grammar` parameter to constrain the model's output to either "yes" or "no". This can be particularly useful in scenarios where the response format needs to be strictly controlled.
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### Example: Binary Response Constraint
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```bash
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curl http://localhost:8080/v1/chat/completions -H "Content-Type: application/json" -d '{
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"model": "gpt-4",
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"messages": [{"role": "user", "content": "Do you like apples?"}],
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"grammar": "root ::= (\"yes\" | \"no\")"
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}'
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```
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In this example, the `grammar` parameter is set to a simple choice between "yes" and "no", ensuring that the model's response adheres strictly to one of these options regardless of the context.
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### Example: JSON Output Constraint
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You can also use grammars to enforce JSON output format:
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```bash
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curl http://localhost:8080/v1/chat/completions -H "Content-Type: application/json" -d '{
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"model": "gpt-4",
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"messages": [{"role": "user", "content": "Generate a person object with name and age"}],
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"grammar": "root ::= \"{\" \"\\\"name\\\":\" string \",\\\"age\\\":\" number \"}\"\nstring ::= \"\\\"\" [a-z]+ \"\\\"\"\nnumber ::= [0-9]+"
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}'
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```
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### Example: YAML Output Constraint
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Similarly, you can enforce YAML format:
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```bash
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curl http://localhost:8080/v1/chat/completions -H "Content-Type: application/json" -d '{
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"model": "gpt-4",
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"messages": [{"role": "user", "content": "Generate a YAML list of fruits"}],
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"grammar": "root ::= \"fruits:\" newline (\" - \" string newline)+\nstring ::= [a-z]+\nnewline ::= \"\\n\""
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}'
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```
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## Advanced Usage
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For more complex grammars, you can define multi-line BNF rules. The grammar parser supports:
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- Alternation (`|`)
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- Repetition (`*`, `+`)
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- Optional elements (`?`)
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- Character classes (`[a-z]`)
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- String literals (`"text"`)
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## Related Features
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- [OpenAI Functions]({{%relref "features/openai-functions" %}}) - Function calling with structured outputs
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- [Text Generation]({{%relref "features/text-generation" %}}) - General text generation capabilities |