transformers/docs/source/en/internal/generation_utils.md

Utilities for Generation

This page lists all the utility functions used by [~generation.GenerationMixin.generate], [~generation.GenerationMixin.greedy_search], [~generation.GenerationMixin.contrastive_search], [~generation.GenerationMixin.sample], [~generation.GenerationMixin.beam_search], [~generation.GenerationMixin.beam_sample], [~generation.GenerationMixin.group_beam_search], and [~generation.GenerationMixin.constrained_beam_search].

Most of those are only useful if you are studying the code of the generate methods in the library.

Generate Outputs

The output of [~generation.GenerationMixin.generate] is an instance of a subclass of [~utils.ModelOutput]. This output is a data structure containing all the information returned by [~generation.GenerationMixin.generate], but that can also be used as tuple or dictionary.

Here's an example:

from transformers import GPT2Tokenizer, GPT2LMHeadModel

tokenizer = GPT2Tokenizer.from_pretrained("gpt2")
model = GPT2LMHeadModel.from_pretrained("gpt2")

inputs = tokenizer("Hello, my dog is cute and ", return_tensors="pt")
generation_output = model.generate(**inputs, return_dict_in_generate=True, output_scores=True)

The generation_output object is a [~generation.GreedySearchDecoderOnlyOutput], as we can see in the documentation of that class below, it means it has the following attributes:

• sequences: the generated sequences of tokens
• scores (optional): the prediction scores of the language modelling head, for each generation step
• hidden_states (optional): the hidden states of the model, for each generation step
• attentions (optional): the attention weights of the model, for each generation step

Here we have the scores since we passed along output_scores=True, but we don't have hidden_states and attentions because we didn't pass output_hidden_states=True or output_attentions=True.

You can access each attribute as you would usually do, and if that attribute has not been returned by the model, you will get None. Here for instance generation_output.scores are all the generated prediction scores of the language modeling head, and generation_output.attentions is None.

When using our generation_output object as a tuple, it only keeps the attributes that don't have None values. Here, for instance, it has two elements, loss then logits, so

generation_output[:2]

will return the tuple (generation_output.sequences, generation_output.scores) for instance.

When using our generation_output object as a dictionary, it only keeps the attributes that don't have None values. Here, for instance, it has two keys that are sequences and scores.

We document here all output types.

GreedySearchOutput

autodoc generation.GreedySearchDecoderOnlyOutput

autodoc generation.GreedySearchEncoderDecoderOutput

autodoc generation.FlaxGreedySearchOutput

SampleOutput

autodoc generation.SampleDecoderOnlyOutput

autodoc generation.SampleEncoderDecoderOutput

autodoc generation.FlaxSampleOutput

BeamSearchOutput

autodoc generation.BeamSearchDecoderOnlyOutput

autodoc generation.BeamSearchEncoderDecoderOutput

BeamSampleOutput

autodoc generation.BeamSampleDecoderOnlyOutput

autodoc generation.BeamSampleEncoderDecoderOutput

LogitsProcessor

A [LogitsProcessor] can be used to modify the prediction scores of a language model head for generation.

autodoc LogitsProcessor - call

autodoc LogitsProcessorList - call

autodoc LogitsWarper - call

autodoc MinLengthLogitsProcessor - call

autodoc MinNewTokensLengthLogitsProcessor - call

autodoc TemperatureLogitsWarper - call

autodoc RepetitionPenaltyLogitsProcessor - call

autodoc TopPLogitsWarper - call

autodoc TopKLogitsWarper - call

autodoc TypicalLogitsWarper - call

autodoc NoRepeatNGramLogitsProcessor - call

autodoc SequenceBiasLogitsProcessor - call

autodoc NoBadWordsLogitsProcessor - call

autodoc PrefixConstrainedLogitsProcessor - call

autodoc HammingDiversityLogitsProcessor - call

autodoc ForcedBOSTokenLogitsProcessor - call

autodoc ForcedEOSTokenLogitsProcessor - call

autodoc InfNanRemoveLogitsProcessor - call

autodoc TFLogitsProcessor - call

autodoc TFLogitsProcessorList - call

autodoc TFLogitsWarper - call

autodoc TFTemperatureLogitsWarper - call

autodoc TFTopPLogitsWarper - call

autodoc TFTopKLogitsWarper - call

autodoc TFMinLengthLogitsProcessor - call

autodoc TFNoBadWordsLogitsProcessor - call

autodoc TFNoRepeatNGramLogitsProcessor - call

autodoc TFRepetitionPenaltyLogitsProcessor - call

autodoc TFForcedBOSTokenLogitsProcessor - call

autodoc TFForcedEOSTokenLogitsProcessor - call

autodoc FlaxLogitsProcessor - call

autodoc FlaxLogitsProcessorList - call

autodoc FlaxLogitsWarper - call

autodoc FlaxTemperatureLogitsWarper - call

autodoc FlaxTopPLogitsWarper - call

autodoc FlaxTopKLogitsWarper - call

autodoc FlaxForcedBOSTokenLogitsProcessor - call

autodoc FlaxForcedEOSTokenLogitsProcessor - call

autodoc FlaxMinLengthLogitsProcessor - call

StoppingCriteria

A [StoppingCriteria] can be used to change when to stop generation (other than EOS token).

autodoc StoppingCriteria - call

autodoc StoppingCriteriaList - call

autodoc MaxLengthCriteria - call

autodoc MaxTimeCriteria - call

Constraints

A [Constraint] can be used to force the generation to include specific tokens or sequences in the output.

autodoc Constraint

autodoc PhrasalConstraint

autodoc DisjunctiveConstraint

autodoc ConstraintListState

BeamSearch

autodoc BeamScorer - process - finalize

autodoc BeamSearchScorer - process - finalize

autodoc ConstrainedBeamSearchScorer - process - finalize

Utilities

autodoc top_k_top_p_filtering

autodoc tf_top_k_top_p_filtering

Streamers

autodoc TextStreamer

autodoc TextIteratorStreamer