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import math
import torch
import transformers
from transformers import LogitsWarper
from transformers.generation.logits_process import (
LogitNormalization,
LogitsProcessor,
LogitsProcessorList,
TemperatureLogitsWarper
)
class TailFreeLogitsWarper(LogitsWarper):
def __init__(self, tfs: float, filter_value: float = -float("Inf"), min_tokens_to_keep: int = 1):
tfs = float(tfs)
if tfs < 0 or tfs > 1.0:
raise ValueError(f"`tfs` has to be a float >= 0 and <= 1, but is {tfs}")
self.tfs = tfs
self.filter_value = filter_value
self.min_tokens_to_keep = min_tokens_to_keep
def __call__(self, input_ids: torch.LongTensor, scores: torch.FloatTensor) -> torch.FloatTensor:
sorted_logits, sorted_indices = torch.sort(scores, descending=True)
probs = sorted_logits.softmax(dim=-1)
# Compute second derivative normalized CDF
d2 = probs.diff().diff().abs()
normalized_d2 = d2 / d2.sum(dim=-1, keepdim=True)
normalized_d2_cdf = normalized_d2.cumsum(dim=-1)
# Remove tokens with CDF value above the threshold (token with 0 are kept)
sorted_indices_to_remove = normalized_d2_cdf > self.tfs
# Centre the distribution around the cutoff as in the original implementation of the algorithm
sorted_indices_to_remove = torch.cat(
(
torch.zeros(scores.shape[0], 1, dtype=torch.bool, device=scores.device),
sorted_indices_to_remove,
torch.ones(scores.shape[0], 1, dtype=torch.bool, device=scores.device),
),
dim=-1,
)
if self.min_tokens_to_keep > 1:
# Keep at least min_tokens_to_keep
sorted_indices_to_remove[..., : self.min_tokens_to_keep] = 0
indices_to_remove = sorted_indices_to_remove.scatter(1, sorted_indices, sorted_indices_to_remove)
scores = scores.masked_fill(indices_to_remove, self.filter_value)
return scores
class TopALogitsWarper(LogitsWarper):
def __init__(self, top_a: float, filter_value: float = -float("Inf"), min_tokens_to_keep: int = 1):
top_a = float(top_a)
if top_a < 0 or top_a > 1.0:
raise ValueError(f"`top_a` has to be a float >= 0 and <= 1, but is {top_a}")
self.top_a = top_a
self.filter_value = filter_value
self.min_tokens_to_keep = min_tokens_to_keep
def __call__(self, input_ids: torch.LongTensor, scores: torch.FloatTensor) -> torch.FloatTensor:
sorted_logits, sorted_indices = torch.sort(scores, descending=True)
probs = sorted_logits.softmax(dim=-1)
# Remove tokens with probability less than top_a*(max(probs))^2 (token with 0 are kept)
probs_max = probs[..., 0, None]
sorted_indices_to_remove = probs < probs_max * probs_max * self.top_a
if self.min_tokens_to_keep > 1:
# Keep at least min_tokens_to_keep
sorted_indices_to_remove[..., : self.min_tokens_to_keep] = 0
indices_to_remove = sorted_indices_to_remove.scatter(1, sorted_indices, sorted_indices_to_remove)
scores = scores.masked_fill(indices_to_remove, self.filter_value)
return scores
class MirostatLogitsWarper(LogitsWarper):
def __init__(self, mirostat_mode: int, mirostat_tau: float, mirostat_eta: float, filter_value: float = -float("Inf"), min_tokens_to_keep: int = 1):
if mirostat_mode not in [2]:
raise ValueError(f"`mirostat` has to be a an integer 2, but is {mirostat_mode}")
self.mirostat_mode = mirostat_mode
self.mirostat_eta = mirostat_eta
self.mirostat_tau = mirostat_tau
self.filter_value = filter_value
self.min_tokens_to_keep = min_tokens_to_keep
self.mu = 2 * self.mirostat_tau
self.e = 0
def __call__(self, input_ids: torch.LongTensor, scores: torch.FloatTensor) -> torch.FloatTensor:
logits = scores[0]
sorted_logits, sorted_indices = torch.sort(logits, descending=True)
prob_original = torch.softmax(sorted_logits, dim=-1).tolist() # candidates
# Truncate the words with surprise values greater than mu
for i, candidate in enumerate(prob_original):
if candidate > 0 and -math.log2(candidate) > self.mu:
if (i == 0):
sorted_logits = sorted_logits[:1]
else:
sorted_logits = sorted_logits[:i]
break
# Normalize the probabilities of the remaining words
prob_topk = torch.softmax(sorted_logits, dim=0)
prev_i = torch.multinomial(prob_topk, num_samples=1, replacement=True).to('cuda')
observed_surprise = -math.log2(prob_topk[prev_i])
self.e = observed_surprise - self.mirostat_tau
# Update mu using the learning rate and error
self.mu -= self.mirostat_eta * self.e
sorted_indices_to_remove = torch.ones_like(scores[0], dtype=torch.bool)
sorted_indices_to_remove[prev_i] = False
indices_to_remove = sorted_indices_to_remove.unsqueeze(0).scatter(1, sorted_indices.unsqueeze(0), sorted_indices_to_remove.unsqueeze(0))
scores = scores.masked_fill(indices_to_remove, self.filter_value)
return scores
class RepetitionPenaltyLogitsProcessorWithRange(LogitsProcessor):
'''
Copied from the transformers library
'''
def __init__(self, penalty: float, _range: int):
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 = penalty
self._range = _range
def __call__(self, input_ids: torch.LongTensor, scores: torch.FloatTensor) -> torch.FloatTensor:
input_ids = input_ids[:, -self._range:]
score = torch.gather(scores, 1, 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, input_ids, score)
return scores
def get_logits_warper_patch(self, generation_config):
warpers = self._get_logits_warper_old(generation_config)
warpers_to_add = LogitsProcessorList()
min_tokens_to_keep = 2 if generation_config.num_beams > 1 else 1
if generation_config.mirostat_mode is not None and generation_config.mirostat_mode == 2:
warpers_to_add.append(MirostatLogitsWarper(mirostat_mode=generation_config.mirostat_mode, mirostat_eta=generation_config.mirostat_eta, mirostat_tau=generation_config.mirostat_tau, min_tokens_to_keep=min_tokens_to_keep))
# We need to disable samplers other than temperature
for warper in warpers:
if not isinstance(warper, TemperatureLogitsWarper):
warpers.remove(warper)
else:
if generation_config.tfs is not None and 0.0 <= generation_config.tfs <= 1.0:
warpers_to_add.append(TailFreeLogitsWarper(tfs=generation_config.tfs, min_tokens_to_keep=min_tokens_to_keep))
if generation_config.top_a is not None and 0.0 <= generation_config.top_a <= 1.0:
warpers_to_add.append(TopALogitsWarper(top_a=generation_config.top_a, min_tokens_to_keep=min_tokens_to_keep))
if warpers and isinstance(warpers[-1], LogitNormalization):
warpers = warpers[:-1] + warpers_to_add + [warpers[-1]]
else:
warpers += warpers_to_add
return warpers
def get_logits_processor_patch(self, **kwargs):
result = self._get_logits_processor_old(**kwargs)
repetition_penalty_range = kwargs['generation_config'].repetition_penalty_range
repetition_penalty = kwargs['generation_config'].repetition_penalty
if repetition_penalty_range > 0:
for i in range(len(result)):
if result[i].__class__.__name__ == 'RepetitionPenaltyLogitsProcessor':
result[i] = RepetitionPenaltyLogitsProcessorWithRange(repetition_penalty, repetition_penalty_range)
return result
def generation_config_init_patch(self, **kwargs):
self.__init___old(**kwargs)
self.tfs = kwargs.pop("tfs", 1.0)
self.top_a = kwargs.pop("top_a", 0.0)
self.mirostat_mode = kwargs.pop("mirostat_mode", 0)
self.mirostat_eta = kwargs.pop("mirostat_eta", 0.1)
self.mirostat_tau = kwargs.pop("mirostat_tau", 5)
self.repetition_penalty_range = kwargs.pop("repetition_penalty_range", 0)
def hijack_samplers():
transformers.GenerationMixin._get_logits_warper_old = transformers.GenerationMixin._get_logits_warper
transformers.GenerationMixin._get_logits_warper = get_logits_warper_patch
transformers.GenerationMixin._get_logits_processor_old = transformers.GenerationMixin._get_logits_processor
transformers.GenerationMixin._get_logits_processor = get_logits_processor_patch
transformers.GenerationConfig.__init___old = transformers.GenerationConfig.__init__
transformers.GenerationConfig.__init__ = generation_config_init_patch
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