Optimized bad word ids (#13433)

* Optimized bad word ids generation

* Fixed optimized bad token ids

* Updated style

src/transformers/generation_logits_process.py

@@ -16,7 +16,7 @@
 import inspect
 import math
 from abc import ABC
-from typing import Callable, Iterable, List
+from typing import Callable, Iterable, List, Optional
 
 import numpy as np
 import torch
@@ -369,46 +369,59 @@ class NoBadWordsLogitsProcessor(LogitsProcessor):
                 f"Each list in `bad_words_ids` has to be a list of positive integers, but is {bad_words_ids}."
             )
 
-        self.bad_words_ids = list(filter(lambda bad_token_seq: bad_token_seq != [eos_token_id], bad_words_ids))
+        bad_words_ids = list(filter(lambda bad_token_seq: bad_token_seq != [eos_token_id], bad_words_ids))
+        self.bad_words_id_length_1 = []
+        self.bad_words_id_length_greater_than_1 = []
+        for word in bad_words_ids:
+            if len(word) == 1:
+                self.bad_words_id_length_1.append(word[0])
+            else:
+                self.bad_words_id_length_greater_than_1.append(word)
+
+        self.static_bad_words_mask: Optional[torch.LongTensor] = None
 
-        for banned_token_seq in self.bad_words_ids:
+        for banned_token_seq in self.bad_words_id_length_greater_than_1:
             assert len(banned_token_seq) > 0, f"Banned words token sequences {bad_words_ids} cannot have an empty list"
 
     def __call__(self, input_ids: torch.LongTensor, scores: torch.FloatTensor) -> torch.FloatTensor:
-        banned_tokens = self._calc_banned_bad_words_ids(input_ids)
-        scores = self._set_scores_to_inf_for_banned_tokens(scores, banned_tokens)
+        if self.static_bad_words_mask is None and len(self.bad_words_id_length_1) > 0:
+            self.static_bad_words_mask = self._calc_static_bad_word_mask(scores)
+
+        dynamic_banned_tokens = self._calc_banned_bad_words_ids(input_ids.tolist())
+        scores = self._set_scores_to_inf_for_banned_tokens(scores, dynamic_banned_tokens)
 
         return scores
 
-    def _tokens_match(self, prev_tokens: torch.LongTensor, tokens: List[int]) -> bool:
+    def _calc_static_bad_word_mask(self, scores: torch.FloatTensor) -> torch.BoolTensor:
+        static_bad_words_mask = torch.zeros(scores.shape[1])
+        static_bad_words_mask[self.bad_words_id_length_1] = 1
+        return static_bad_words_mask.unsqueeze(0).to(scores.device).bool()
+
+    def _tokens_match(self, prev_tokens: List[int], tokens: List[int]) -> bool:
         if len(tokens) == 0:
             # if bad word tokens is just one token always ban it
             return True
         elif len(tokens) > len(prev_tokens):
             # if bad word tokens are longer then prev input_ids they can't be equal
             return False
-        elif prev_tokens[-len(tokens) :].tolist() == tokens:
-            # if tokens match
-            return True
         else:
-            return False
+            return prev_tokens[-len(tokens) :] == tokens
 
-    def _calc_banned_bad_words_ids(self, prev_input_ids: Iterable[int]) -> Iterable[int]:
+    def _calc_banned_bad_words_ids(self, prev_input_ids: List[List[int]]) -> Iterable[int]:
         banned_tokens = []
         for prev_input_ids_slice in prev_input_ids:
             banned_tokens_slice = []
-            for banned_token_seq in self.bad_words_ids:
-                if self._tokens_match(prev_input_ids_slice, banned_token_seq[:-1]) is False:
-                    # if tokens do not match continue
-                    continue
-
+            for banned_token_seq in self.bad_words_id_length_greater_than_1:
+                if self._tokens_match(prev_input_ids_slice, banned_token_seq[:-1]):
                     banned_tokens_slice.append(banned_token_seq[-1])
 
             banned_tokens.append(banned_tokens_slice)
 
         return banned_tokens
 
-    def _set_scores_to_inf_for_banned_tokens(self, scores: torch.Tensor, banned_tokens: List[List[int]]) -> None:
+    def _set_scores_to_inf_for_banned_tokens(
+        self, scores: torch.Tensor, banned_tokens: List[List[int]]
+    ) -> torch.Tensor:
         """
         Modifies the scores in place by setting the banned token positions to `-inf`. Banned token is expected to be a
         list of list of banned tokens to ban in the format [[batch index, vocabulary position],...
@@ -428,9 +441,11 @@ class NoBadWordsLogitsProcessor(LogitsProcessor):
                         f"An invalid bad word ID is defined: {token}. This ID is not contained in the"
                         f"vocabulary, and is therefore ignored."
                     )
-        if not banned_mask_list:
+        if not banned_mask_list and self.static_bad_words_mask is None:
             return scores
 
+        else:
+            if banned_mask_list:
                 banned_mask = torch.LongTensor(banned_mask_list)
                 indices = torch.ones(len(banned_mask))
                 # A sparse tensor is generated from a list of coordinates: [[0, 1], [0, 2], [2, 0]]. A conversion to dense tensor generates:
@@ -439,8 +454,17 @@ class NoBadWordsLogitsProcessor(LogitsProcessor):
                 # [ 1  0  0 ]
 
                 banned_mask = (
-            torch.sparse.LongTensor(banned_mask.t(), indices, scores.size()).to(scores.device).to_dense().bool()
+                    torch.sparse.LongTensor(banned_mask.t(), indices, scores.size())
+                    .to(scores.device)
+                    .to_dense()
+                    .bool()
                 )
+
+                if self.static_bad_words_mask is not None:
+                    banned_mask = torch.bitwise_or(banned_mask, self.static_bad_words_mask)
+            else:
+                banned_mask = self.static_bad_words_mask
+
             scores = scores.masked_fill(banned_mask, -float("inf"))
             return scores