Skip to content

xgrammar

Backend class for XGrammar.

XGrammarBackend

Bases: BaseBackend

Backend for XGRammar.

Source code in outlines/backends/xgrammar.py 
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
class XGrammarBackend(BaseBackend):
    """Backend for XGRammar."""

    def __init__(self, model: SteerableModel):
        """
        Parameters
        ----------
        model
            The Outlines model of the user.

        """
        import xgrammar as xgr
        from transformers import AutoConfig

        if not isinstance(model, Transformers):
            raise ValueError(
                "The xgrammar backend only supports Transformers models"
            )

        vocab_size = AutoConfig.from_pretrained(
            model.model.config._name_or_path
        ).vocab_size
        tokenizer_info = xgr.TokenizerInfo.from_huggingface(
            model.hf_tokenizer,
            vocab_size=vocab_size
        )
        self.grammar_compiler = xgr.GrammarCompiler(tokenizer_info)

    def get_json_schema_logits_processor(
        self, json_schema: str
    ) -> "LogitsProcessor":
        """Create a logits processor from a JSON schema.

        Parameters
        ----------
        json_schema: str
            The JSON schema to create a logits processor from.

        Returns
        -------
        LogitsProcessor
            The logits processor to use to constrain the generation.

        """
        compiled_grammar = self.grammar_compiler.compile_json_schema(
            json_schema
        )
        return XGrammarLogitsProcessor(compiled_grammar)

    def get_regex_logits_processor(self, regex: str) -> "LogitsProcessor":
        """Create a logits processor from a regex.

        Parameters
        ----------
        regex: str
            The regex to create a logits processor from.

        Returns
        -------
        LogitsProcessor
            The logits processor to use to constrain the generation.

        """
        compiled_grammar = self.grammar_compiler.compile_regex(regex)
        return XGrammarLogitsProcessor(compiled_grammar)

    def get_cfg_logits_processor(self, grammar: str) -> "LogitsProcessor":
        """Create a logits processor from a context-free grammar.

        Parameters
        ----------
        grammar: str
            The context-free grammar to create a logits processor from.

        Returns
        -------
        LogitsProcessor
            The logits processor to use to constrain the generation.

        """
        compiled_grammar = self.grammar_compiler.compile_grammar(grammar)
        return XGrammarLogitsProcessor(compiled_grammar)

    def get_fsm_logits_processor(self, fsm):
        raise NotImplementedError(
            "XGrammarBackend does not support FSM logits processors. "
            "Use the outlines_core backend instead."
        )

__init__(model)

Parameters:

Name Type Description Default
model SteerableModel

The Outlines model of the user.

 required
Source code in outlines/backends/xgrammar.py 
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
def __init__(self, model: SteerableModel):
    """
    Parameters
    ----------
    model
        The Outlines model of the user.

    """
    import xgrammar as xgr
    from transformers import AutoConfig

    if not isinstance(model, Transformers):
        raise ValueError(
            "The xgrammar backend only supports Transformers models"
        )

    vocab_size = AutoConfig.from_pretrained(
        model.model.config._name_or_path
    ).vocab_size
    tokenizer_info = xgr.TokenizerInfo.from_huggingface(
        model.hf_tokenizer,
        vocab_size=vocab_size
    )
    self.grammar_compiler = xgr.GrammarCompiler(tokenizer_info)

get_cfg_logits_processor(grammar)

Create a logits processor from a context-free grammar.

Parameters:

Name Type Description Default
grammar str

The context-free grammar to create a logits processor from.

 required

Returns:

Type Description
LogitsProcessor

The logits processor to use to constrain the generation.
Source code in outlines/backends/xgrammar.py 
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
def get_cfg_logits_processor(self, grammar: str) -> "LogitsProcessor":
    """Create a logits processor from a context-free grammar.

    Parameters
    ----------
    grammar: str
        The context-free grammar to create a logits processor from.

    Returns
    -------
    LogitsProcessor
        The logits processor to use to constrain the generation.

    """
    compiled_grammar = self.grammar_compiler.compile_grammar(grammar)
    return XGrammarLogitsProcessor(compiled_grammar)

get_json_schema_logits_processor(json_schema)

Create a logits processor from a JSON schema.

Parameters:

Name Type Description Default
json_schema str

The JSON schema to create a logits processor from.

 required

Returns:

Type Description
LogitsProcessor

The logits processor to use to constrain the generation.
Source code in outlines/backends/xgrammar.py 
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
def get_json_schema_logits_processor(
    self, json_schema: str
) -> "LogitsProcessor":
    """Create a logits processor from a JSON schema.

    Parameters
    ----------
    json_schema: str
        The JSON schema to create a logits processor from.

    Returns
    -------
    LogitsProcessor
        The logits processor to use to constrain the generation.

    """
    compiled_grammar = self.grammar_compiler.compile_json_schema(
        json_schema
    )
    return XGrammarLogitsProcessor(compiled_grammar)

get_regex_logits_processor(regex)

Create a logits processor from a regex.

Parameters:

Name Type Description Default
regex str

The regex to create a logits processor from.

 required

Returns:

Type Description
LogitsProcessor

The logits processor to use to constrain the generation.
Source code in outlines/backends/xgrammar.py 
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
def get_regex_logits_processor(self, regex: str) -> "LogitsProcessor":
    """Create a logits processor from a regex.

    Parameters
    ----------
    regex: str
        The regex to create a logits processor from.

    Returns
    -------
    LogitsProcessor
        The logits processor to use to constrain the generation.

    """
    compiled_grammar = self.grammar_compiler.compile_regex(regex)
    return XGrammarLogitsProcessor(compiled_grammar)

XGrammarLogitsProcessor

Bases: OutlinesLogitsProcessor

Logits processor for XGrammar.

This class wraps the xgr.contrib.hf.LogitsProcessor class and adds a reset method to reset the logits processor for a new generation.

Source code in outlines/backends/xgrammar.py 
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
class XGrammarLogitsProcessor(OutlinesLogitsProcessor):
    """Logits processor for XGrammar.

    This class wraps the `xgr.contrib.hf.LogitsProcessor` class and adds
    a `reset` method to reset the logits processor for a new generation.

    """

    def __init__(self, compiled_grammar: str):
        """
        Parameters
        ----------
        compiled_grammar: str
            The compiled grammar to use to create the logits processor.

        """
        import xgrammar as xgr

        self.xgr = xgr
        self.compiled_grammar = compiled_grammar
        self.xgrammar_logits_processor = None
        super().__init__("torch")

    def reset(self):
        """Reset the logits processor for a new generation."""
        self.xgrammar_logits_processor = None

    def process_logits(self, input_ids: TensorType, logits: TensorType) -> TensorType:
        """Bias the logits."""
        if self.xgrammar_logits_processor is None:
            self.xgrammar_logits_processor = self.xgr.contrib.hf.LogitsProcessor(
                self.compiled_grammar
            )
        return self.xgrammar_logits_processor(input_ids, logits) # type: ignore

__init__(compiled_grammar)

Parameters:

Name Type Description Default
compiled_grammar str

The compiled grammar to use to create the logits processor.

 required
Source code in outlines/backends/xgrammar.py 
25
26
27
28
29
30
31
32
33
34
35
36
37
38
def __init__(self, compiled_grammar: str):
    """
    Parameters
    ----------
    compiled_grammar: str
        The compiled grammar to use to create the logits processor.

    """
    import xgrammar as xgr

    self.xgr = xgr
    self.compiled_grammar = compiled_grammar
    self.xgrammar_logits_processor = None
    super().__init__("torch")

process_logits(input_ids, logits)

Bias the logits.

Source code in outlines/backends/xgrammar.py 
44
45
46
47
48
49
50
def process_logits(self, input_ids: TensorType, logits: TensorType) -> TensorType:
    """Bias the logits."""
    if self.xgrammar_logits_processor is None:
        self.xgrammar_logits_processor = self.xgr.contrib.hf.LogitsProcessor(
            self.compiled_grammar
        )
    return self.xgrammar_logits_processor(input_ids, logits) # type: ignore

reset()

Reset the logits processor for a new generation.

Source code in outlines/backends/xgrammar.py 
40
41
42
def reset(self):
    """Reset the logits processor for a new generation."""
    self.xgrammar_logits_processor = None