Repository: huggingface/transformers

Issue:
Add seed to data collator classes
### Feature request

I opened an issue for setting a seed for `DataCollatorForLanguageModeling` which would help reproducibility in pretraining encoder-only transformers without setting a global seed at https://github.com/huggingface/transformers/issues/36357, with a PR that also got approved (https://github.com/huggingface/transformers/pull/36497). 

I see that there is scope to add this seed feature to other data collator classes, namely `DataCollatorForWholeWordMask` and `DataCollatorForPermutationLanguageModeling`, where there are pseudo-random functions involved in the collator.

### Motivation

This feature would help reproducibility in data preparation without setting a global seed as in `transformers.set_seed`. This has advantages as I have pointed out in https://github.com/huggingface/transformers/issues/36357.

### Your contribution

Since I was involved with the seed feature in `DataCollatorForLanguageModeling`, I'm very familiar with this idea and I'd love to make PRs adding this feature to the other two collators!

Discussion:

Solution patch:
diff --git a/src/transformers/data/data_collator.py b/src/transformers/data/data_collator.py
index dce6991365..07490a25f9 100644
--- a/src/transformers/data/data_collator.py
+++ b/src/transformers/data/data_collator.py
@@ -1193,6 +1193,11 @@ class DataCollatorForWholeWordMask(DataCollatorForLanguageModeling):
     </Tip>"""
 
     def torch_call(self, examples: List[Union[List[int], Any, Dict[str, Any]]]) -> Dict[str, Any]:
+        if self.seed and self.generator is None:
+            # If we have a seed, we need to create a generator object. Subsequent calls to this function will use the same generator.
+            # If no seed supplied, we will use the global RNG
+            self.create_rng()
+
         if isinstance(examples[0], Mapping):
             input_ids = [e["input_ids"] for e in examples]
         else:
@@ -1223,6 +1228,11 @@ class DataCollatorForWholeWordMask(DataCollatorForLanguageModeling):
     def tf_call(self, examples: List[Union[List[int], Any, Dict[str, Any]]]) -> Dict[str, Any]:
         import tensorflow as tf
 
+        if self.seed and self.generator is None:
+            # If we have a seed, we need to create a generator object. Subsequent calls to this function will use the same generator.
+            # If no seed supplied, we will use the global RNG
+            self.create_rng()
+
         if isinstance(examples[0], Mapping):
             input_ids = [e["input_ids"] for e in examples]
         else:
@@ -1251,6 +1261,11 @@ class DataCollatorForWholeWordMask(DataCollatorForLanguageModeling):
         return {"input_ids": inputs, "labels": labels}
 
     def numpy_call(self, examples: List[Union[List[int], Any, Dict[str, Any]]]) -> Dict[str, Any]:
+        if self.seed and self.generator is None:
+            # If we have a seed, we need to create a generator object. Subsequent calls to this function will use the same generator.
+            # If no seed supplied, we will use the global RNG
+            self.create_rng()
+
         if isinstance(examples[0], Mapping):
             input_ids = [e["input_ids"] for e in examples]
         else:
@@ -1278,6 +1293,30 @@ class DataCollatorForWholeWordMask(DataCollatorForLanguageModeling):
         inputs, labels = self.numpy_mask_tokens(batch_input, batch_mask)
         return {"input_ids": inputs, "labels": labels}
 
+    def _shuffle(self, cand_indexes):
+        # if no seed, just use random's shuffle
+        if self.seed is None:
+            random.shuffle(cand_indexes)
+            return cand_indexes
+
+        # if seed is provided, use the generator to shuffle
+        if self.return_tensors == "pt":
+            import torch
+
+            indices = torch.randperm(len(cand_indexes), generator=self.generator)
+            return [cand_indexes[i] for i in indices]
+
+        elif self.return_tensors == "tf":
+            import tensorflow as tf
+
+            seed = self.generator.make_seeds(2)[0]
+            indices = tf.random.experimental.stateless_shuffle(tf.range(len(cand_indexes)), seed=seed).numpy().tolist()
+            return [cand_indexes[i] for i in indices]
+
+        elif self.return_tensors == "np":
+            self.generator.shuffle(cand_indexes)
+            return cand_indexes
+
     def _whole_word_mask(self, input_tokens: List[str], max_predictions=512):
         """
         Get 0/1 labels for masked tokens with whole word mask proxy
@@ -1298,7 +1337,7 @@ class DataCollatorForWholeWordMask(DataCollatorForLanguageModeling):
             else:
                 cand_indexes.append([i])
 
-        random.shuffle(cand_indexes)
+        cand_indexes = self._shuffle(cand_indexes)
         num_to_predict = min(max_predictions, max(1, int(round(len(input_tokens) * self.mlm_probability))))
         masked_lms = []
         covered_indexes = set()
@@ -1346,16 +1385,32 @@ class DataCollatorForWholeWordMask(DataCollatorForLanguageModeling):
         masked_indices = probability_matrix.bool()
         labels[~masked_indices] = -100  # We only compute loss on masked tokens
 
-        # 80% of the time, we replace masked input tokens with tokenizer.mask_token ([MASK])
-        indices_replaced = torch.bernoulli(torch.full(labels.shape, 0.8)).bool() & masked_indices
+        # mask_replace_prob% of the time, we replace masked input tokens with tokenizer.mask_token ([MASK])
+        indices_replaced = (
+            torch.bernoulli(torch.full(labels.shape, self.mask_replace_prob), generator=self.generator).bool()
+            & masked_indices
+        )
         inputs[indices_replaced] = self.tokenizer.convert_tokens_to_ids(self.tokenizer.mask_token)
 
-        # 10% of the time, we replace masked input tokens with random word
-        indices_random = torch.bernoulli(torch.full(labels.shape, 0.5)).bool() & masked_indices & ~indices_replaced
-        random_words = torch.randint(len(self.tokenizer), labels.shape, dtype=torch.long)
+        if self.mask_replace_prob == 1 or self.random_replace_prob == 0:
+            return inputs, labels
+
+        remaining_prob = 1 - self.mask_replace_prob
+        # scaling the random_replace_prob to the remaining probability for example if
+        # mask_replace_prob = 0.8 and random_replace_prob = 0.1,
+        # then random_replace_prob_scaled = 0.1 / 0.2 = 0.5
+        random_replace_prob_scaled = self.random_replace_prob / remaining_prob
+
+        # random_replacement_prob% of the time, we replace masked input tokens with random word
+        indices_random = (
+            torch.bernoulli(torch.full(labels.shape, random_replace_prob_scaled), generator=self.generator).bool()
+            & masked_indices
+            & ~indices_replaced
+        )
+        random_words = torch.randint(len(self.tokenizer), labels.shape, dtype=torch.long, generator=self.generator)
         inputs[indices_random] = random_words[indices_random]
 
-        # The rest of the time (10% of the time) we keep the masked input tokens unchanged
+        # The rest of the time ((1-random_replacement_prob-mask_replace_prob)% of the time) we keep the masked input tokens unchanged
         return inputs, labels
 
     def tf_mask_tokens(self, inputs: Any, mask_labels: Any) -> Tuple[Any, Any]:
@@ -1387,17 +1442,35 @@ class DataCollatorForWholeWordMask(DataCollatorForLanguageModeling):
         # Replace unmasked indices with -100 in the labels since we only compute loss on masked tokens
         labels = tf.where(masked_indices, inputs, -100)
 
-        # 80% of the time, we replace masked input tokens with tokenizer.mask_token ([MASK])
-        indices_replaced = self.tf_bernoulli(input_shape, 0.8) & masked_indices
+        # mask_replace_prob% of the time, we replace masked input tokens with tokenizer.mask_token ([MASK])
+        indices_replaced = self.tf_bernoulli(input_shape, self.mask_replace_prob, self.generator) & masked_indices
 
         inputs = tf.where(indices_replaced, self.tokenizer.mask_token_id, inputs)
 
-        # 10% of the time, we replace masked input tokens with random word
-        indices_random = self.tf_bernoulli(input_shape, 0.5) & masked_indices & ~indices_replaced
-        random_words = tf.random.uniform(input_shape, maxval=len(self.tokenizer), dtype=tf.int64)
+        if self.mask_replace_prob == 1 or self.random_replace_prob == 0:
+            return inputs, labels
+
+        remaining_prob = 1 - self.mask_replace_prob
+        # scaling the random_replace_prob to the remaining probability for example if
+        # mask_replace_prob = 0.8 and random_replace_prob = 0.1,
+        # then random_replace_prob_scaled = 0.1 / 0.2 = 0.5
+        random_replace_prob_scaled = self.random_replace_prob / remaining_prob
+
+        # random_replace_prob% of the time, we replace masked input tokens with random word
+        indices_random = (
+            self.tf_bernoulli(input_shape, random_replace_prob_scaled, self.generator)
+            & masked_indices
+            & ~indices_replaced
+        )
+
+        if self.generator:
+            random_words = self.generator.uniform(input_shape, maxval=len(self.tokenizer), dtype=tf.int64)
+        else:
+            random_words = tf.random.uniform(input_shape, maxval=len(self.tokenizer), dtype=tf.int64)
+
         inputs = tf.where(indices_random, random_words, inputs)
 
-        # The rest of the time (10% of the time) we keep the masked input tokens unchanged
+        # The rest of the time ((1-mask_replace_prob-random_replace_prob)% of the time) we keep the masked input tokens unchanged
         return inputs, labels
 
     def numpy_mask_tokens(self, inputs: Any, mask_labels: Any) -> Tuple[Any, Any]:
@@ -1425,19 +1498,44 @@ class DataCollatorForWholeWordMask(DataCollatorForLanguageModeling):
 
         labels[~masked_indices] = -100  # We only compute loss on masked tokens
 
-        # 80% of the time, we replace masked input tokens with tokenizer.mask_token ([MASK])
-        indices_replaced = np.random.binomial(1, 0.8, size=labels.shape).astype(bool) & masked_indices
+        # mask_replacement_prob% of the time, we replace masked input tokens with tokenizer.mask_token ([MASK])
+        if self.generator:
+            indices_replaced = (
+                self.generator.binomial(1, self.mask_replace_prob, size=labels.shape).astype(bool) & masked_indices
+            )
+        else:
+            indices_replaced = (
+                np.random.binomial(1, self.mask_replace_prob, size=labels.shape).astype(bool) & masked_indices
+            )
         inputs[indices_replaced] = self.tokenizer.convert_tokens_to_ids(self.tokenizer.mask_token)
 
-        # 10% of the time, we replace masked input tokens with random word
-        # indices_random = torch.bernoulli(torch.full(labels.shape, 0.5)).bool() & masked_indices & ~indices_replaced
-        indices_random = (
-            np.random.binomial(1, 0.5, size=labels.shape).astype(bool) & masked_indices & ~indices_replaced
-        )
-        random_words = np.random.randint(low=0, high=len(self.tokenizer), size=labels.shape, dtype=np.int64)
+        if self.mask_replace_prob == 1 or self.random_replace_prob == 0:
+            return inputs, labels
+
+        remaining_prob = 1 - self.mask_replace_prob
+        # scaling the random_replace_prob to the remaining probability for example if
+        # mask_replace_prob = 0.8 and random_replace_prob = 0.1,
+        # then random_replace_prob_scaled = 0.1 / 0.2 = 0.5
+        random_replace_prob_scaled = self.random_replace_prob / remaining_prob
+
+        if self.generator:
+            indices_random = (
+                self.generator.binomial(1, random_replace_prob_scaled, size=labels.shape).astype(bool)
+                & masked_indices
+                & ~indices_replaced
+            )
+            random_words = self.generator.integers(low=0, high=len(self.tokenizer), size=labels.shape, dtype=np.int64)
+        else:
+            indices_random = (
+                np.random.binomial(1, random_replace_prob_scaled, size=labels.shape).astype(bool)
+                & masked_indices
+                & ~indices_replaced
+            )
+            random_words = np.random.randint(low=0, high=len(self.tokenizer), size=labels.shape, dtype=np.int64)
+
         inputs[indices_random] = random_words[indices_random]
 
-        # The rest of the time (10% of the time) we keep the masked input tokens unchanged
+        # The rest of the time ((1-mask_replace_prob-random_replace_prob)% of the time) we keep the masked input tokens unchanged
         return inputs, labels
 
 


Test patch:
diff --git a/tests/trainer/test_data_collator.py b/tests/trainer/test_data_collator.py
index ca88b3c79c..a88641ca16 100644
--- a/tests/trainer/test_data_collator.py
+++ b/tests/trainer/test_data_collator.py
@@ -445,6 +445,86 @@ class DataCollatorIntegrationTest(unittest.TestCase):
         self.assertEqual(batch["input_ids"].shape, torch.Size((2, 10)))
         self.assertEqual(batch["labels"].shape, torch.Size((2, 10)))
 
+    def test_data_collator_for_whole_word_mask_with_seed(self):
+        tokenizer = BertTokenizer(self.vocab_file)
+        features = [{"input_ids": list(range(1000))}, {"input_ids": list(range(1000))}]
+
+        # check if seed is respected between two different DataCollatorForWholeWordMask instances
+        data_collator = DataCollatorForWholeWordMask(tokenizer, seed=42)
+        batch_1 = data_collator(features)
+        self.assertEqual(batch_1["input_ids"].shape, torch.Size((2, 1000)))
+        self.assertEqual(batch_1["labels"].shape, torch.Size((2, 1000)))
+
+        data_collator = DataCollatorForWholeWordMask(tokenizer, seed=42)
+        batch_2 = data_collator(features)
+        self.assertEqual(batch_2["input_ids"].shape, torch.Size((2, 1000)))
+        self.assertEqual(batch_2["labels"].shape, torch.Size((2, 1000)))
+
+        self.assertTrue(torch.all(batch_1["input_ids"] == batch_2["input_ids"]))
+        self.assertTrue(torch.all(batch_1["labels"] == batch_2["labels"]))
+
+        # check if seed is respected in multiple workers situation
+        features = [{"input_ids": list(range(1000))} for _ in range(10)]
+        dataloader = torch.utils.data.DataLoader(
+            features,
+            batch_size=2,
+            num_workers=2,
+            generator=torch.Generator().manual_seed(42),
+            collate_fn=DataCollatorForWholeWordMask(tokenizer, seed=42),
+        )
+
+        batch_3_input_ids = []
+        batch_3_labels = []
+        for batch in dataloader:
+            batch_3_input_ids.append(batch["input_ids"])
+            batch_3_labels.append(batch["labels"])
+
+        batch_3_input_ids = torch.stack(batch_3_input_ids)
+        batch_3_labels = torch.stack(batch_3_labels)
+        self.assertEqual(batch_3_input_ids.shape, torch.Size((5, 2, 1000)))
+        self.assertEqual(batch_3_labels.shape, torch.Size((5, 2, 1000)))
+
+        dataloader = torch.utils.data.DataLoader(
+            features,
+            batch_size=2,
+            num_workers=2,
+            collate_fn=DataCollatorForWholeWordMask(tokenizer, seed=42),
+        )
+
+        batch_4_input_ids = []
+        batch_4_labels = []
+        for batch in dataloader:
+            batch_4_input_ids.append(batch["input_ids"])
+            batch_4_labels.append(batch["labels"])
+        batch_4_input_ids = torch.stack(batch_4_input_ids)
+        batch_4_labels = torch.stack(batch_4_labels)
+        self.assertEqual(batch_4_input_ids.shape, torch.Size((5, 2, 1000)))
+        self.assertEqual(batch_4_labels.shape, torch.Size((5, 2, 1000)))
+
+        self.assertTrue(torch.all(batch_3_input_ids == batch_4_input_ids))
+        self.assertTrue(torch.all(batch_3_labels == batch_4_labels))
+
+        # try with different seed
+        dataloader = torch.utils.data.DataLoader(
+            features,
+            batch_size=2,
+            num_workers=2,
+            collate_fn=DataCollatorForWholeWordMask(tokenizer, seed=43),
+        )
+
+        batch_5_input_ids = []
+        batch_5_labels = []
+        for batch in dataloader:
+            batch_5_input_ids.append(batch["input_ids"])
+            batch_5_labels.append(batch["labels"])
+        batch_5_input_ids = torch.stack(batch_5_input_ids)
+        batch_5_labels = torch.stack(batch_5_labels)
+        self.assertEqual(batch_5_input_ids.shape, torch.Size((5, 2, 1000)))
+        self.assertEqual(batch_5_labels.shape, torch.Size((5, 2, 1000)))
+
+        self.assertFalse(torch.all(batch_3_input_ids == batch_5_input_ids))
+        self.assertFalse(torch.all(batch_3_labels == batch_5_labels))
+
     def test_plm(self):
         tokenizer = BertTokenizer(self.vocab_file)
         no_pad_features = [{"input_ids": list(range(10))}, {"input_ids": list(range(10))}]
@@ -1199,6 +1279,33 @@ class TFDataCollatorIntegrationTest(unittest.TestCase):
         self.assertEqual(batch["input_ids"].shape.as_list(), [2, 10])
         self.assertEqual(batch["labels"].shape.as_list(), [2, 10])
 
+    def test_data_collator_for_whole_word_mask_with_seed(self):
+        tokenizer = BertTokenizer(self.vocab_file)
+        features = [{"input_ids": list(range(1000))}, {"input_ids": list(range(1000))}]
+
+        # check if seed is respected between two different DataCollatorForWholeWordMask instances
+        data_collator = DataCollatorForWholeWordMask(tokenizer, seed=42, return_tensors="tf")
+        batch_1 = data_collator(features)
+        self.assertEqual(batch_1["input_ids"].shape.as_list(), [2, 1000])
+        self.assertEqual(batch_1["labels"].shape.as_list(), [2, 1000])
+
+        data_collator = DataCollatorForWholeWordMask(tokenizer, seed=42, return_tensors="tf")
+        batch_2 = data_collator(features)
+        self.assertEqual(batch_2["input_ids"].shape.as_list(), [2, 1000])
+        self.assertEqual(batch_2["labels"].shape.as_list(), [2, 1000])
+
+        self.assertTrue(np.all(batch_1["input_ids"] == batch_2["input_ids"]))
+        self.assertTrue(np.all(batch_1["labels"] == batch_2["labels"]))
+
+        # try with different seed
+        data_collator = DataCollatorForWholeWordMask(tokenizer, seed=43, return_tensors="tf")
+        batch_3 = data_collator(features)
+        self.assertEqual(batch_3["input_ids"].shape.as_list(), [2, 1000])
+        self.assertEqual(batch_3["labels"].shape.as_list(), [2, 1000])
+
+        self.assertFalse(np.all(batch_1["input_ids"] == batch_3["input_ids"]))
+        self.assertFalse(np.all(batch_1["labels"] == batch_3["labels"]))
+
     def test_plm(self):
         tokenizer = BertTokenizer(self.vocab_file)
         no_pad_features = [{"input_ids": list(range(10))}, {"input_ids": list(range(10))}]
@@ -1920,6 +2027,32 @@ class NumpyDataCollatorIntegrationTest(unittest.TestCase):
         self.assertEqual(batch["input_ids"].shape, (2, 10))
         self.assertEqual(batch["labels"].shape, (2, 10))
 
+    def test_data_collator_for_whole_word_mask_with_seed(self):
+        tokenizer = BertTokenizer(self.vocab_file)
+        features = [{"input_ids": list(range(1000))}, {"input_ids": list(range(1000))}]
+
+        # check if seed is respected between two different DataCollatorForWholeWordMask instances
+        data_collator = DataCollatorForWholeWordMask(tokenizer, seed=42, return_tensors="np")
+        batch_1 = data_collator(features)
+        self.assertEqual(batch_1["input_ids"].shape, (2, 1000))
+        self.assertEqual(batch_1["labels"].shape, (2, 1000))
+
+        data_collator = DataCollatorForWholeWordMask(tokenizer, seed=42, return_tensors="np")
+        batch_2 = data_collator(features)
+        self.assertEqual(batch_2["input_ids"].shape, (2, 1000))
+        self.assertEqual(batch_2["labels"].shape, (2, 1000))
+
+        self.assertTrue(np.all(batch_1["input_ids"] == batch_2["input_ids"]))
+        self.assertTrue(np.all(batch_1["labels"] == batch_2["labels"]))
+
+        data_collator = DataCollatorForWholeWordMask(tokenizer, seed=43, return_tensors="np")
+        batch_3 = data_collator(features)
+        self.assertEqual(batch_3["input_ids"].shape, (2, 1000))
+        self.assertEqual(batch_3["labels"].shape, (2, 1000))
+
+        self.assertFalse(np.all(batch_1["input_ids"] == batch_3["input_ids"]))
+        self.assertFalse(np.all(batch_1["labels"] == batch_3["labels"]))
+
     def test_plm(self):
         tokenizer = BertTokenizer(self.vocab_file)
         no_pad_features = [{"input_ids": list(range(10))}, {"input_ids": list(range(10))}]