Add hallucination filter (#18675)

* Add hallucination penalty

* Make quality changes

* Inverse penalty

* Fix imports & quality

* Fix name spelling issue

* set encoder_repetition_penalty and fix quality

* Fix failing test

* Add to config_common_kwargs

* Fix modelling_rag error

* Update src/transformers/generation_logits_process.py
Co-authored-by: Joao Gante <joaofranciscocardosogante@gmail.com>

* Remove breakpoint

* Make style fixes

* Update encoder_repetition_penalty default value

* Merge latest main changes

* Make fixup changes

* Add EncoderRepetitionPenaltyLogitsProcessor to generation/__init__.py

* Fix repo-inconsistency

* Remove venv

* Remove tensorflow-macos & add tests

* Add documentation

* Fix quality issues

* move encoder_repetition_penalty to config

* Update src/transformers/configuration_utils.py
Co-authored-by: Joao Gante <joaofranciscocardosogante@gmail.com>

* Update src/transformers/generation/configuration_utils.py
Co-authored-by: Joao Gante <joaofranciscocardosogante@gmail.com>

* Remove encoder_repetition_penalty from tests

* Fix type error

* Fix format error
Co-authored-by: Joao Gante <joaofranciscocardosogante@gmail.com>

src/transformers/generation/__init__.py

@@ -58,6 +58,7 @@ else:
         "NoRepeatNGramLogitsProcessor",
         "PrefixConstrainedLogitsProcessor",
         "RepetitionPenaltyLogitsProcessor",
+        "EncoderRepetitionPenaltyLogitsProcessor",
         "TemperatureLogitsWarper",
         "TopKLogitsWarper",
         "TopPLogitsWarper",
@@ -164,6 +165,7 @@ if TYPE_CHECKING:
         from .beam_search import BeamHypotheses, BeamScorer, BeamSearchScorer, ConstrainedBeamSearchScorer
         from .logits_process import (
             EncoderNoRepeatNGramLogitsProcessor,
+            EncoderRepetitionPenaltyLogitsProcessor,
             EpsilonLogitsWarper,
             EtaLogitsWarper,
             ExponentialDecayLengthPenalty,

src/transformers/generation/configuration_utils.py

@@ -127,6 +127,9 @@ class GenerationConfig(PushToHubMixin):
         repetition_penalty (`float`, *optional*, defaults to 1.0):
             The parameter for repetition penalty. 1.0 means no penalty. See [this
             paper](https://arxiv.org/pdf/1909.05858.pdf) for more details.
+        encoder_repetition_penalty (`float`, *optional*, defaults to 1.0):
+            The paramater for encoder_repetition_penalty. An exponential penalty on sequences that are not in the
+            original input. 1.0 means no penalty.
         length_penalty (`float`, *optional*, defaults to 1.0):
             Exponential penalty to the length that is used with beam-based generation. It is applied as an exponent to
             the sequence length, which in turn is used to divide the score of the sequence. Since the score is the log
@@ -239,6 +242,7 @@ class GenerationConfig(PushToHubMixin):
         self.eta_cutoff = kwargs.pop("eta_cutoff", 0.0)
         self.diversity_penalty = kwargs.pop("diversity_penalty", 0.0)
         self.repetition_penalty = kwargs.pop("repetition_penalty", 1.0)
+        self.encoder_repetition_penalty = kwargs.pop("encoder_repetition_penalty", 1.0)
         self.length_penalty = kwargs.pop("length_penalty", 1.0)
         self.no_repeat_ngram_size = kwargs.pop("no_repeat_ngram_size", 0)
         self.bad_words_ids = kwargs.pop("bad_words_ids", None)

src/transformers/generation/logits_process.py

@@ -204,6 +204,34 @@ class RepetitionPenaltyLogitsProcessor(LogitsProcessor):
         return scores
 
 
+class EncoderRepetitionPenaltyLogitsProcessor(LogitsProcessor):
+    r"""
+    [`LogitsProcessor`] enforcing an exponential penalty on tokens that are not in the original input.
+
+    Args:
+        hallucination_penalty (`float`):
+            The parameter for hallucination penalty. 1.0 means no penalty.
+        encoder_input_ids (`torch.LongTensor`):
+            The encoder_input_ids that should not be repeated within the decoder ids.
+    """
+
+    def __init__(self, penalty: float, encoder_input_ids: torch.LongTensor):
+        if not isinstance(penalty, float) or not (penalty > 0):
+            raise ValueError(f"`penalty` has to be a strictly positive float, but is {penalty}")
+
+        self.penalty = 1 / penalty
+        self.encoder_input_ids = encoder_input_ids
+
+    def __call__(self, input_ids: torch.LongTensor, scores: torch.FloatTensor) -> torch.FloatTensor:
+        score = torch.gather(scores, 1, self.encoder_input_ids)
+
+        # if score < 0 then repetition penalty has to be multiplied to reduce the previous token probability
+        score = torch.where(score < 0, score * self.penalty, score / self.penalty)
+
+        scores.scatter_(1, self.encoder_input_ids, score)
+        return scores
+
+
 class TopPLogitsWarper(LogitsWarper):
     """
     [`LogitsWarper`] that performs top-p, i.e. restricting to top tokens summing to prob_cut_off <= prob_cut_off.

src/transformers/generation/utils.py

@@ -39,6 +39,7 @@ from .beam_search import BeamScorer, BeamSearchScorer, ConstrainedBeamSearchScor
 from .configuration_utils import GenerationConfig
 from .logits_process import (
     EncoderNoRepeatNGramLogitsProcessor,
+    EncoderRepetitionPenaltyLogitsProcessor,
     EpsilonLogitsWarper,
     EtaLogitsWarper,
     ExponentialDecayLengthPenalty,
@@ -799,6 +800,15 @@ class GenerationMixin:
                     num_beam_groups=generation_config.num_beam_groups,
                 )
             )
+        if (
+            generation_config.encoder_repetition_penalty is not None
+            and generation_config.encoder_repetition_penalty != 1.0
+        ):
+            processors.append(
+                EncoderRepetitionPenaltyLogitsProcessor(
+                    penalty=generation_config.encoder_repetition_penalty, encoder_input_ids=encoder_input_ids
+                )
+            )
         if generation_config.repetition_penalty is not None and generation_config.repetition_penalty != 1.0:
             processors.append(RepetitionPenaltyLogitsProcessor(penalty=generation_config.repetition_penalty))
         if generation_config.no_repeat_ngram_size is not None and generation_config.no_repeat_ngram_size > 0:

tests/generation/test_logits_process.py

@@ -28,6 +28,7 @@ if is_torch_available():
 
     from transformers.generation import (
         EncoderNoRepeatNGramLogitsProcessor,
+        EncoderRepetitionPenaltyLogitsProcessor,
         EpsilonLogitsWarper,
         EtaLogitsWarper,
         ExponentialDecayLengthPenalty,
@@ -175,6 +176,31 @@ class LogitsProcessorTest(unittest.TestCase):
         self.assertAlmostEqual(scores[1, 0].item(), (1 / vocab_size) / 2)
         self.assertAlmostEqual(scores[1, 5].item(), (4 / vocab_size) / 2)
 
+    def test_encoder_repetition_penalty_dist_process(self):
+        input_ids = torch.tensor([[0, 1], [5, 0]], device=torch_device, dtype=torch.long)
+        vocab_size = 10
+
+        scores = self._get_uniform_logits(batch_size=2, length=vocab_size)
+
+        # give values special values
+        scores[0, 0] = -(1 / vocab_size)
+        scores[1, 5] = 4 / vocab_size
+
+        rep_penalty_proc = EncoderRepetitionPenaltyLogitsProcessor(penalty=2.0, encoder_input_ids=input_ids)
+
+        scores = rep_penalty_proc(input_ids, scores.clone())
+
+        # check that values were correctly changed
+        self.assertAlmostEqual(scores[0, 0].item(), -(1 / vocab_size) / 2)
+        self.assertAlmostEqual(scores[0, 1].item(), (1 / vocab_size) * 2)
+
+        self.assertAlmostEqual(scores[1, 0].item(), (1 / vocab_size) * 2)
+        self.assertAlmostEqual(scores[1, 5].item(), (4 / vocab_size) * 2)
+
+        # check that values not in the encoder ids were NOT changed
+        self.assertAlmostEqual(scores[0, 2].item(), (1 / vocab_size))
+        self.assertAlmostEqual(scores[1, 2].item(), (1 / vocab_size))
+
     def test_top_k_dist_warper(self):
         input_ids = None
         vocab_size = 10