Improve special_token_id logic in run_generation.py and add tests (#2885)

* improving generation

* finalized special token behaviour for no_beam_search generation

* solved modeling_utils merge conflict

* solve merge conflicts in modeling_utils.py

* add run_generation improvements from PR #2749

* adapted language generation to not use hardcoded -1 if no padding token is available

* remove the -1 removal as hard coded -1`s are not necessary anymore

* add lightweight language generation testing for randomely initialized models - just checking whether no errors are thrown

* add slow language generation tests for pretrained models using hardcoded output with pytorch seed

* delete ipdb

* check that all generated tokens are valid

* renaming

* renaming Generation -> Generate

* make style

* updated so that generate_beam_search has same token behavior than generate_no_beam_search

* consistent return format for run_generation.py

* deleted pretrain lm generate tests -> will be added in another PR

* cleaning of unused if statements and renaming

* run_generate will always return an iterable

* make style

* consistent renaming

* improve naming, make sure generate function always returns the same tensor, add docstring

* add slow tests for all lmhead models

* make style and improve example comments modeling_utils

* better naming and refactoring in modeling_utils

* improving generation

* finalized special token behaviour for no_beam_search generation

* solved modeling_utils merge conflict

* solve merge conflicts in modeling_utils.py

* add run_generation improvements from PR #2749

* adapted language generation to not use hardcoded -1 if no padding token is available

* remove the -1 removal as hard coded -1`s are not necessary anymore

* add lightweight language generation testing for randomely initialized models - just checking whether no errors are thrown

* add slow language generation tests for pretrained models using hardcoded output with pytorch seed

* delete ipdb

* check that all generated tokens are valid

* renaming

* renaming Generation -> Generate

* make style

* updated so that generate_beam_search has same token behavior than generate_no_beam_search

* consistent return format for run_generation.py

* deleted pretrain lm generate tests -> will be added in another PR

* cleaning of unused if statements and renaming

* run_generate will always return an iterable

* make style

* consistent renaming

* improve naming, make sure generate function always returns the same tensor, add docstring

* add slow tests for all lmhead models

* make style and improve example comments modeling_utils

* better naming and refactoring in modeling_utils

* changed fast random lm generation testing design to more general one

* delete in old testing design in gpt2

* correct old variable name

* temporary fix for encoder_decoder lm generation tests - has to be updated when t5 is fixed

* adapted all fast random generate tests to new design

* better warning description in modeling_utils

* better comment

* better comment and error message

Co-authored-by: Thomas Wolf <thomwolf@users.noreply.github.com>

examples/run_generation.py

@@ -106,6 +106,8 @@ def prepare_xlm_input(args, model, tokenizer, prompt_text):
             language = None
             while language not in available_languages:
                 language = input("Using XLM. Select language in " + str(list(available_languages)) + " >>> ")
+
+        model.config.lang_id = model.config.lang2id[language]
         # kwargs["language"] = tokenizer.lang2id[language]
 
     # TODO fix mask_token_id setup when configurations will be synchronized between models and tokenizers
@@ -119,12 +121,12 @@ def prepare_xlm_input(args, model, tokenizer, prompt_text):
 
 def prepare_xlnet_input(args, _, tokenizer, prompt_text):
     prompt_text = (args.padding_text if args.padding_text else PADDING_TEXT) + prompt_text
-    return prompt_text, {}
+    return prompt_text
 
 
 def prepare_transfoxl_input(args, _, tokenizer, prompt_text):
     prompt_text = (args.padding_text if args.padding_text else PADDING_TEXT) + prompt_text
-    return prompt_text, {}
+    return prompt_text
 
 
 PREPROCESSING_FUNCTIONS = {
@@ -183,6 +185,7 @@ def main():
 
     parser.add_argument("--seed", type=int, default=42, help="random seed for initialization")
     parser.add_argument("--no_cuda", action="store_true", help="Avoid using CUDA when available")
+    parser.add_argument("--num_return_sequences", type=int, default=1, help="The number of samples to generate.")
     args = parser.parse_args()
 
     args.device = torch.device("cuda" if torch.cuda.is_available() and not args.no_cuda else "cpu")
@@ -210,28 +213,48 @@ def main():
     requires_preprocessing = args.model_type in PREPROCESSING_FUNCTIONS.keys()
     if requires_preprocessing:
         prepare_input = PREPROCESSING_FUNCTIONS.get(args.model_type)
-        prompt_text = prepare_input(args, model, tokenizer, prompt_text)
+        preprocessed_prompt_text = prepare_input(args, model, tokenizer, prompt_text)
-    encoded_prompt = tokenizer.encode(prompt_text, add_special_tokens=False, return_tensors="pt")
+        encoded_prompt = tokenizer.encode(preprocessed_prompt_text, add_special_tokens=False, return_tensors="pt")
+    else:
+        encoded_prompt = tokenizer.encode(prompt_text, add_special_tokens=False, return_tensors="pt")
     encoded_prompt = encoded_prompt.to(args.device)
 
     output_sequences = model.generate(
         input_ids=encoded_prompt,
-        max_length=args.length,
+        max_length=args.length + len(encoded_prompt[0]),
         temperature=args.temperature,
         top_k=args.k,
         top_p=args.p,
         repetition_penalty=args.repetition_penalty,
         do_sample=True,
+        num_return_sequences=args.num_return_sequences,
     )
 
-    # Batch size == 1. to add more examples please use num_return_sequences > 1
+    # Remove the batch dimension when returning multiple sequences
-    generated_sequence = output_sequences[0].tolist()
+    if len(output_sequences.shape) > 2:
-    text = tokenizer.decode(generated_sequence, clean_up_tokenization_spaces=True)
+        output_sequences.squeeze_()
-    text = text[: text.find(args.stop_token) if args.stop_token else None]
 
-    print(text)
+    generated_sequences = []
 
-    return text
+    for generated_sequence_idx, generated_sequence in enumerate(output_sequences):
+        print("=== GENERATED SEQUENCE {} ===".format(generated_sequence_idx + 1))
+        generated_sequence = generated_sequence.tolist()
+
+        # Decode text
+        text = tokenizer.decode(generated_sequence, clean_up_tokenization_spaces=True)
+
+        # Remove all text after the stop token
+        text = text[: text.find(args.stop_token) if args.stop_token else None]
+
+        # Add the prompt at the beginning of the sequence. Remove the excess text that was used for pre-processing
+        total_sequence = (
+            prompt_text + text[len(tokenizer.decode(encoded_prompt[0], clean_up_tokenization_spaces=True)) :]
+        )
+
+        generated_sequences.append(total_sequence)
+        print(total_sequence)
+
+    return generated_sequences
 
 
 if __name__ == "__main__":

examples/test_examples.py

@@ -97,4 +97,4 @@ class ExamplesTests(unittest.TestCase):
         model_type, model_name = ("--model_type=openai-gpt", "--model_name_or_path=openai-gpt")
         with patch.object(sys, "argv", testargs + [model_type, model_name]):
             result = run_generation.main()
-            self.assertGreaterEqual(len(result), 10)
+            self.assertGreaterEqual(len(result[0]), 10)

src/transformers/configuration_utils.py

@@ -75,9 +75,9 @@ class PretrainedConfig(object):
         self.top_k = kwargs.pop("top_k", 50)
         self.top_p = kwargs.pop("top_p", 1.0)
         self.repetition_penalty = kwargs.pop("repetition_penalty", 1.0)
-        self.bos_token_id = kwargs.pop("bos_token_id", 0)
+        self.bos_token_id = kwargs.pop("bos_token_id", None)
-        self.pad_token_id = kwargs.pop("pad_token_id", 0)
+        self.pad_token_id = kwargs.pop("pad_token_id", None)
-        self.eos_token_ids = kwargs.pop("eos_token_ids", 0)
+        self.eos_token_ids = kwargs.pop("eos_token_ids", None)
         self.length_penalty = kwargs.pop("length_penalty", 1.0)
         self.num_return_sequences = kwargs.pop("num_return_sequences", 1)
 

src/transformers/modeling_utils.py

@@ -645,33 +645,39 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin):
             num_return_sequences: (`optional`) int
                 The number of independently computed returned sequences for each element in the batch. Default to 1.
 
+        Return:
+
+            output: `torch.LongTensor` of shape `(batch_size * num_return_sequences, sequence_length)`
+                sequence_length is either equal to max_length or shorter if all batches finished early due to the `eos_token_id`
+
         Examples::
 
             tokenizer = AutoTokenizer.from_pretrained('distilgpt2')   # Initialize tokenizer
             model = AutoModelWithLMHead.from_pretrained('distilgpt2')    # Download model and configuration from S3 and cache.
-            outputs = model.generate(max_length=40, bos_token_id=tokenizer.bos_token_id, eos_token_ids=tokenizer.eos_token_id)  # do greedy decoding without beam search
+            outputs = model.generate(max_length=40, bos_token_id=tokenizer.bos_token_id, eos_token_ids=tokenizer.eos_token_id, do_sample=False)  # do greedy decoding
             print('Generated: {}'.format(tokenizer.decode(outputs[0], skip_special_tokens=True)))
 
             tokenizer = AutoTokenizer.from_pretrained('openai-gpt')   # Initialize tokenizer
             model = AutoModelWithLMHead.from_pretrained('openai-gpt')    # Download model and configuration from S3 and cache.
             input_context = 'The dog'
             input_ids = torch.tensor(tokenizer.encode(input_context)).unsqueeze(0)  # encode input context
-            outputs = model.generate(input_ids=input_ids, do_sample=True, num_beams=5, num_return_sequences=3, temperature=1.5)  # generate 3 independent sequences using beam search decoding (5 beams) with sampling from initial context 'The dog'
+            outputs = model.generate(input_ids=input_ids, num_beams=5, num_return_sequences=3, temperature=1.5)  # generate 3 independent sequences using beam search decoding (5 beams) with sampling from initial context 'The dog'
             for i in range(3): #  3 output sequences were generated
-                print('Generated {}: {}'.format(i, tokenizer.decode(outputs[0][i], skip_special_tokens=True)))
+                print('Generated {}: {}'.format(i, tokenizer.decode(outputs[i], skip_special_tokens=True)))
 
             tokenizer = AutoTokenizer.from_pretrained('distilgpt2')   # Initialize tokenizer
             model = AutoModelWithLMHead.from_pretrained('distilgpt2')    # Download model and configuration from S3 and cache.
             input_context = 'The dog'
             input_ids = torch.tensor(tokenizer.encode(input_context)).unsqueeze(0)  # encode input context
-            outputs = model.generate(input_ids=input_ids, max_length=40, temperature=0.7, bos_token_id=tokenizer.bos_token_id, eos_token_ids=tokenizer.eos_token_id, num_beams=3)  # generate sequences using greedy beam search decoding (3 beams)
+            outputs = model.generate(input_ids=input_ids, max_length=40, temperature=0.7, bos_token_id=tokenizer.bos_token_id, pad_token_id=tokenizer.pad_token_id, eos_token_ids=tokenizer.eos_token_id, num_return_sequences=3)  # 3 generate sequences using by sampling
-            print('Generated: {}'.format(tokenizer.decode(outputs[0], skip_special_tokens=True)))
+            for i in range(3): #  3 output sequences were generated
+                print('Generated {}: {}'.format(i, tokenizer.decode(outputs[i], skip_special_tokens=True)))
 
             tokenizer = AutoTokenizer.from_pretrained('ctrl')   # Initialize tokenizer
             model = AutoModelWithLMHead.from_pretrained('ctrl')    # Download model and configuration from S3 and cache.
             input_context = 'Legal My neighbor is'  # "Legal" is one of the control codes for ctrl
             input_ids = torch.tensor(tokenizer.encode(input_context)).unsqueeze(0)  # encode input context
-            outputs = model.generate(input_ids=input_ids, max_length=50, temperature=0.7, repetition_penalty=1.2)  # generate sequences using using greedy search
+            outputs = model.generate(input_ids=input_ids, max_length=50, temperature=0.7, repetition_penalty=1.2)  # generate sequences
             print('Generated: {}'.format(tokenizer.decode(outputs[0], skip_special_tokens=True)))
 
         """
@@ -712,10 +718,14 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin):
         assert isinstance(top_k, int) and top_k >= 0, "`top_k` should be a positive integer."
         assert 0 <= top_p <= 1, "`top_p` should be between 0 and 1."
         assert repetition_penalty >= 1.0, "`repetition_penalty` should be >= 1."
-        assert isinstance(bos_token_id, int) and bos_token_id >= 0, "`bos_token_id` should be a positive integer."
+        assert input_ids is not None or (
-        assert isinstance(pad_token_id, int) and pad_token_id >= 0, "`pad_token_id` should be a positive integer."
+            isinstance(bos_token_id, int) and bos_token_id >= 0
-        assert isinstance(eos_token_ids, (list, tuple)) and (
+        ), "If input_ids is not defined, `bos_token_id` should be a positive integer."
-            e >= 0 for e in eos_token_ids
+        assert pad_token_id is None or (
+            isinstance(pad_token_id, int) and (pad_token_id >= 0)
+        ), "`pad_token_id` should be a positive integer."
+        assert (eos_token_ids is None) or (
+            isinstance(eos_token_ids, (list, tuple)) and ((isinstance(e, int) and e >= 0) for e in eos_token_ids)
         ), "`eos_token_ids` should be a positive integer or a list/tuple of positive integers."
         assert length_penalty > 0, "`length_penalty` should be strictely positive."
         assert (
@@ -723,12 +733,22 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin):
         ), "`num_return_sequences` should be a strictely positive integer."
 
         if input_ids is None:
+            assert isinstance(bos_token_id, int) and bos_token_id >= 0, (
+                "you should either supply a context to complete as `input_ids` input "
+                "or a `bos_token_id` (integer >= 0) as a first token to start the generation."
+            )
             input_ids = torch.full(
                 (batch_size, 1), bos_token_id, dtype=torch.long, device=next(self.parameters()).device
             )
         else:
             assert input_ids.dim() == 2, "Input prompt should be of shape (batch_size, sequence length)."
 
+        if pad_token_id is None and eos_token_ids is not None:
+            logger.warning(
+                "Setting `pad_token_id` to {} (first `eos_token_id`) to generate sequence".format(eos_token_ids[0])
+            )
+            pad_token_id = eos_token_ids[0]
+
         # current position and vocab size
         cur_len = input_ids.shape[1]
         vocab_size = self.config.vocab_size
@@ -775,8 +795,6 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin):
                 effective_batch_size,
             )
 
-        if num_return_sequences != 1:
-            output = output.view(batch_size, num_return_sequences, -1)
         return output
 
     def _generate_no_beam_search(
@@ -798,6 +816,7 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin):
         """
         # current position / max lengths / length of generated sentences / unfinished sentences
         unfinished_sents = input_ids.new(batch_size).fill_(1)
+        sent_lengths = input_ids.new(batch_size).fill_(max_length)
 
         past = None
 
@@ -833,21 +852,41 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin):
                 next_token = torch.argmax(next_token_logits, dim=-1)
 
             # update generations and finished sentences
-            tokens_to_add = next_token * unfinished_sents + pad_token_id * (1 - unfinished_sents)
+            if eos_token_ids is not None:
+                # pad finished sentences if eos_token_ids exist
+                tokens_to_add = next_token * unfinished_sents + (pad_token_id) * (1 - unfinished_sents)
+            else:
+                tokens_to_add = next_token
+
             input_ids = torch.cat([input_ids, tokens_to_add.unsqueeze(-1)], dim=-1)
-            for eos_token_id in eos_token_ids:
+
-                unfinished_sents.mul_(tokens_to_add.ne(eos_token_id).long())
+            if eos_token_ids is not None:
+                for eos_token_id in eos_token_ids:
+                    eos_in_sents = tokens_to_add == eos_token_id
+                    # if sentence is unfinished and the token to add is eos, sent_lengths is filled with current length
+                    is_sents_unfinished_and_token_to_add_is_eos = unfinished_sents.mul(eos_in_sents.long()).bool()
+                    sent_lengths.masked_fill_(is_sents_unfinished_and_token_to_add_is_eos, cur_len + 1)
+                    # unfinished_sents is set to zero if eos in sentence
+                    unfinished_sents.mul_((~eos_in_sents).long())
+
             cur_len = cur_len + 1
 
             # stop when there is a </s> in each sentence, or if we exceed the maximul length
             if unfinished_sents.max() == 0:
                 break
 
-        # add eos_token_ids to unfinished sentences
+        # if there are different sentences lengths in the batch, some batches have to be padded
-        if cur_len == max_length:
+        if sent_lengths.min().item() != sent_lengths.max().item():
-            input_ids[:, -1].masked_fill_(unfinished_sents.to(dtype=torch.bool), eos_token_ids[0])
+            assert pad_token_id is not None, "`Pad_token_id` has to be defined if batches have different lengths"
+            # finished sents are filled with pad_token
+            decoded = input_ids.new(batch_size, sent_lengths.max().item()).fill_(pad_token_id)
+        else:
+            decoded = input_ids
 
-        return input_ids
+        for hypo_idx, hypo in enumerate(input_ids):
+            decoded[hypo_idx, : sent_lengths[hypo_idx]] = hypo[: sent_lengths[hypo_idx]]
+
+        return decoded
 
     def _generate_beam_search(
         self,
@@ -941,11 +980,19 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin):
             next_batch_beam = []
 
             # for each sentence
-            for batch_ex in range(batch_size):
+            for batch_idx in range(batch_size):
 
                 # if we are done with this sentence
-                done[batch_ex] = done[batch_ex] or generated_hyps[batch_ex].is_done(next_scores[batch_ex].max().item())
+                done[batch_idx] = done[batch_idx] or generated_hyps[batch_idx].is_done(
-                if done[batch_ex]:
+                    next_scores[batch_idx].max().item()
+                )
+                if done[batch_idx]:
+                    assert (
+                        len(generated_hyps[batch_idx]) >= num_beams
+                    ), "Batch can only be done if at least {} beams have been generated".format(num_beams)
+                    assert (
+                        eos_token_ids is not None and pad_token_id is not None
+                    ), "generated beams >= num_beams -> eos_token_id and pad_token have to be defined"
                     next_batch_beam.extend([(0, pad_token_id, 0)] * num_beams)  # pad the batch
                     continue
 
@@ -953,30 +1000,29 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin):
                 next_sent_beam = []
 
                 # next words for this sentence
-                for idx, score in zip(next_words[batch_ex], next_scores[batch_ex]):
+                for idx, score in zip(next_words[batch_idx], next_scores[batch_idx]):
 
                     # get beam and word IDs
                     beam_id = idx // vocab_size
                     word_id = idx % vocab_size
 
-                    # end of sentence, or next word
+                    # add to generated hypotheses if end of sentence or last iteration
-                    if word_id.item() in eos_token_ids or cur_len + 1 == max_length:
+                    if eos_token_ids is not None and word_id.item() in eos_token_ids:
-                        generated_hyps[batch_ex].add(
+                        generated_hyps[batch_idx].add(
-                            input_ids[batch_ex * num_beams + beam_id, :cur_len].clone(), score.item()
+                            input_ids[batch_idx * num_beams + beam_id, :cur_len].clone(), score.item()
                         )
                     else:
-                        next_sent_beam.append((score, word_id, batch_ex * num_beams + beam_id))
+                        # add next predicted word if it is not eos_token
+                        next_sent_beam.append((score, word_id, batch_idx * num_beams + beam_id))
 
                     # the beam for next step is full
                     if len(next_sent_beam) == num_beams:
                         break
 
                 # update next beam content
-                assert len(next_sent_beam) == 0 if cur_len + 1 == max_length else num_beams
+                assert len(next_sent_beam) == num_beams, "Beam should always be full"
-                if len(next_sent_beam) == 0:
-                    next_sent_beam = [(0, pad_token_id, 0)] * num_beams  # pad the batch
                 next_batch_beam.extend(next_sent_beam)
-                assert len(next_batch_beam) == num_beams * (batch_ex + 1)
+                assert len(next_batch_beam) == num_beams * (batch_idx + 1)
 
             # sanity check / prepare next batch
             assert len(next_batch_beam) == batch_size * num_beams
@@ -1008,29 +1054,42 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin):
             if all(done):
                 break
 
-        # visualize hypotheses
+        for batch_idx in range(batch_size):
-        # print([len(x) for x in generated_hyps], cur_len)
+            # Add all open beam hypothesis to generated_hyps
-        # globals().update( locals() );
+            if not done[batch_idx]:
-        # !import code; code.interact(local=vars())
+                for idx, score in zip(next_words[batch_idx], next_scores[batch_idx]):
-        # for ii in range(batch_size):
+
-        #     for ss, ww in sorted(generated_hyps[ii].hyp, key=lambda x: x[0], reverse=True):
+                    # get beam and word IDs
-        #         print("%.3f " % ss + " ".join(self.dico[x] for x in ww.tolist()))
+                    beam_id = idx // vocab_size
-        #     print("")
+                    word_id = idx % vocab_size
+                    generated_hyps[batch_idx].add(
+                        input_ids[batch_idx * num_beams + beam_id, :cur_len].clone(), score.item()
+                    )
 
         # select the best hypotheses
-        tgt_len = input_ids.new(batch_size)
+        sent_lengths = input_ids.new(batch_size)
         best = []
 
         for i, hypotheses in enumerate(generated_hyps):
-            best_hyp = max(hypotheses.hyp, key=lambda x: x[0])[1]
+            best_hyp = max(hypotheses.beams, key=lambda x: x[0])[1]
-            tgt_len[i] = len(best_hyp) + 1  # +1 for the <EOS> symbol
+            sent_lengths[i] = len(best_hyp)
             best.append(best_hyp)
 
-        # generate target batch
+        # shorter batches are filled with pad_token
-        decoded = input_ids.new(batch_size, tgt_len.max().item()).fill_(pad_token_id)
+        if sent_lengths.min().item() != sent_lengths.max().item():
-        for i, hypo in enumerate(best):
+            assert pad_token_id is not None, "`Pad_token_id` has to be defined"
-            decoded[i, : tgt_len[i] - 1] = hypo
+            sent_max_len = min(sent_lengths.max().item() + 1, max_length)
-            decoded[i, tgt_len[i] - 1] = eos_token_ids[0]
+            decoded = input_ids.new(batch_size, sent_max_len).fill_(pad_token_id)
+
+            # fill with hypothesis and eos_token_id if necessary
+            for i, hypo in enumerate(best):
+                decoded[i, : sent_lengths[i]] = hypo
+                if sent_lengths[i] < max_length:
+                    decoded[i, sent_lengths[i]] = eos_token_ids[0]
+        else:
+            # none of the hypotheses have an eos_token
+            assert (len(hypo) == max_length for hypo in best)
+            decoded = torch.stack(best).type(torch.long).to(next(self.parameters()).device)
 
         return decoded
 
@@ -1071,33 +1130,33 @@ def top_k_top_p_filtering(logits, top_k=0, top_p=1.0, filter_value=-float("Inf")
 
 
 class BeamHypotheses(object):
-    def __init__(self, n_hyp, max_length, length_penalty, early_stopping):
+    def __init__(self, num_beams, max_length, length_penalty, early_stopping):
         """
         Initialize n-best list of hypotheses.
         """
         self.max_length = max_length - 1  # ignoring bos_token
         self.length_penalty = length_penalty
         self.early_stopping = early_stopping
-        self.n_hyp = n_hyp
+        self.num_beams = num_beams
-        self.hyp = []
+        self.beams = []
         self.worst_score = 1e9
 
     def __len__(self):
         """
         Number of hypotheses in the list.
         """
-        return len(self.hyp)
+        return len(self.beams)
 
     def add(self, hyp, sum_logprobs):
         """
         Add a new hypothesis to the list.
         """
         score = sum_logprobs / len(hyp) ** self.length_penalty
-        if len(self) < self.n_hyp or score > self.worst_score:
+        if len(self) < self.num_beams or score > self.worst_score:
-            self.hyp.append((score, hyp))
+            self.beams.append((score, hyp))
-            if len(self) > self.n_hyp:
+            if len(self) > self.num_beams:
-                sorted_scores = sorted([(s, idx) for idx, (s, _) in enumerate(self.hyp)])
+                sorted_scores = sorted([(s, idx) for idx, (s, _) in enumerate(self.beams)])
-                del self.hyp[sorted_scores[0][1]]
+                del self.beams[sorted_scores[0][1]]
                 self.worst_score = sorted_scores[1][0]
             else:
                 self.worst_score = min(score, self.worst_score)
@@ -1107,7 +1166,7 @@ class BeamHypotheses(object):
         If there are enough hypotheses and that none of the hypotheses being generated
         can become better than the worst one in the heap, then we are done with this sentence.
         """
-        if len(self) < self.n_hyp:
+        if len(self) < self.num_beams:
             return False
         elif self.early_stopping:
             return True

tests/test_modeling_common.py

@@ -13,7 +13,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-
 import copy
 import logging
 import os.path
@@ -53,6 +52,7 @@ class ModelTesterMixin:
 
     model_tester = None
     all_model_classes = ()
+    all_generative_model_classes = ()
     test_torchscript = True
     test_pruning = True
     test_resize_embeddings = True
@@ -595,6 +595,47 @@ class ModelTesterMixin:
             with torch.no_grad():
                 model(**inputs_dict)
 
+    def test_lm_head_model_random_generate(self):
+
+        config, inputs_dict = self.model_tester.prepare_config_and_inputs_for_common()
+        input_ids = inputs_dict.get(
+            "input_ids", None
+        )  # TODO (PVP): ugly workaround to make code work for t5 for the moment - has to changed when t5 is fixed.
+
+        for model_class in self.all_generative_model_classes:
+            model = model_class(config)
+            model.to(torch_device)
+            model.eval()
+
+            if config.bos_token_id is None:
+                with self.assertRaises(AssertionError):
+                    model.generate(max_length=5)
+                # batch_size = 1
+                self._check_generated_tokens(model.generate(input_ids))
+                # batch_size = 1, num_beams > 1
+                self._check_generated_tokens(model.generate(input_ids, num_beams=3))
+            else:
+                # batch_size = 1
+                self._check_generated_tokens(model.generate(max_length=5))
+                # batch_size = 1, num_beams > 1
+                self._check_generated_tokens(model.generate(max_length=5, num_beams=3))
+
+            # batch_size > 1, sample
+            self._check_generated_tokens(model.generate(input_ids, num_return_sequences=3))
+            # batch_size > 1, greedy
+            self._check_generated_tokens(model.generate(input_ids, do_sample=False, num_return_sequences=3))
+            # batch_size > 1, num_beams > 1, sample
+            self._check_generated_tokens(model.generate(input_ids, num_beams=3, num_return_sequences=3,))
+            # batch_size > 1, num_beams > 1, greedy
+            self._check_generated_tokens(
+                model.generate(input_ids, do_sample=False, num_beams=3, num_return_sequences=3)
+            )
+
+    def _check_generated_tokens(self, output_ids):
+        for token_id in output_ids[0].tolist():
+            self.assertGreaterEqual(token_id, 0)
+            self.assertLess(token_id, self.model_tester.vocab_size)
+
 
 global_rng = random.Random()
 

tests/test_modeling_ctrl.py

@@ -30,6 +30,7 @@ if is_torch_available():
 class CTRLModelTest(ModelTesterMixin, unittest.TestCase):
 
     all_model_classes = (CTRLModel, CTRLLMHeadModel) if is_torch_available() else ()
+    all_generative_model_classes = (CTRLLMHeadModel,) if is_torch_available() else ()
     test_pruning = False
     test_torchscript = False
     test_resize_embeddings = False

tests/test_modeling_gpt2.py

@@ -37,6 +37,9 @@ if is_torch_available():
 class GPT2ModelTest(ModelTesterMixin, unittest.TestCase):
 
     all_model_classes = (GPT2Model, GPT2LMHeadModel, GPT2DoubleHeadsModel) if is_torch_available() else ()
+    all_generative_model_classes = (
+        (GPT2LMHeadModel,) if is_torch_available() else ()
+    )  # TODO (PVP): Add Double HeadsModel when generate() function is changed accordingly
 
     class GPT2ModelTester(object):
         def __init__(
@@ -88,6 +91,8 @@ class GPT2ModelTest(ModelTesterMixin, unittest.TestCase):
             self.num_labels = num_labels
             self.num_choices = num_choices
             self.scope = scope
+            self.bos_token_id = vocab_size - 1
+            self.eos_token_id = vocab_size - 1
 
         def prepare_config_and_inputs(self):
             input_ids = ids_tensor([self.batch_size, self.seq_length], self.vocab_size)
@@ -122,9 +127,11 @@ class GPT2ModelTest(ModelTesterMixin, unittest.TestCase):
                 # hidden_dropout_prob=self.hidden_dropout_prob,
                 # attention_probs_dropout_prob=self.attention_probs_dropout_prob,
                 n_positions=self.max_position_embeddings,
-                n_ctx=self.max_position_embeddings
+                n_ctx=self.max_position_embeddings,
                 # type_vocab_size=self.type_vocab_size,
                 # initializer_range=self.initializer_range
+                bos_token_id=self.bos_token_id,
+                eos_token_ids=self.eos_token_id,
             )
 
             head_mask = ids_tensor([self.num_hidden_layers, self.num_attention_heads], 2)

tests/test_modeling_openai.py

@@ -39,6 +39,9 @@ class OpenAIGPTModelTest(ModelTesterMixin, unittest.TestCase):
     all_model_classes = (
         (OpenAIGPTModel, OpenAIGPTLMHeadModel, OpenAIGPTDoubleHeadsModel) if is_torch_available() else ()
     )
+    all_generative_model_classes = (
+        (OpenAIGPTLMHeadModel,) if is_torch_available() else ()
+    )  # TODO (PVP): Add Double HeadsModel when generate() function is changed accordingly
 
     class OpenAIGPTModelTester(object):
         def __init__(

tests/test_modeling_transfo_xl.py

@@ -34,6 +34,7 @@ if is_torch_available():
 class TransfoXLModelTest(ModelTesterMixin, unittest.TestCase):
 
     all_model_classes = (TransfoXLModel, TransfoXLLMHeadModel) if is_torch_available() else ()
+    all_generative_model_classes = (TransfoXLLMHeadModel,) if is_torch_available() else ()
     test_pruning = False
     test_torchscript = False
     test_resize_embeddings = False
@@ -59,6 +60,7 @@ class TransfoXLModelTest(ModelTesterMixin, unittest.TestCase):
             num_hidden_layers=5,
             scope=None,
             seed=1,
+            eos_token_id=0,
         ):
             self.parent = parent
             self.batch_size = batch_size
@@ -79,6 +81,7 @@ class TransfoXLModelTest(ModelTesterMixin, unittest.TestCase):
             self.num_hidden_layers = num_hidden_layers
             self.scope = scope
             self.seed = seed
+            self.eos_token_id = eos_token_id
 
         def prepare_config_and_inputs(self):
             input_ids_1 = ids_tensor([self.batch_size, self.seq_length], self.vocab_size)
@@ -100,6 +103,7 @@ class TransfoXLModelTest(ModelTesterMixin, unittest.TestCase):
                 d_inner=self.d_inner,
                 div_val=self.div_val,
                 n_layer=self.num_hidden_layers,
+                eos_token_ids=self.eos_token_id,
             )
 
             return (config, input_ids_1, input_ids_2, lm_labels)

tests/test_modeling_xlm.py

@@ -49,6 +49,9 @@ class XLMModelTest(ModelTesterMixin, unittest.TestCase):
         if is_torch_available()
         else ()
     )
+    all_generative_model_classes = (
+        (XLMWithLMHeadModel,) if is_torch_available() else ()
+    )  # TODO (PVP): Check other models whether language generation is also applicable
 
     class XLMModelTester(object):
         def __init__(
@@ -81,6 +84,7 @@ class XLMModelTest(ModelTesterMixin, unittest.TestCase):
             summary_type="last",
             use_proj=True,
             scope=None,
+            bos_token_id=0,
         ):
             self.parent = parent
             self.batch_size = batch_size
@@ -111,6 +115,7 @@ class XLMModelTest(ModelTesterMixin, unittest.TestCase):
             self.num_labels = num_labels
             self.num_choices = num_choices
             self.scope = scope
+            self.bos_token_id = bos_token_id
 
         def prepare_config_and_inputs(self):
             input_ids = ids_tensor([self.batch_size, self.seq_length], self.vocab_size)
@@ -151,6 +156,7 @@ class XLMModelTest(ModelTesterMixin, unittest.TestCase):
                 initializer_range=self.initializer_range,
                 summary_type=self.summary_type,
                 use_proj=self.use_proj,
+                bos_token_id=self.bos_token_id,
             )
 
             return (

tests/test_modeling_xlnet.py

@@ -52,6 +52,9 @@ class XLNetModelTest(ModelTesterMixin, unittest.TestCase):
         if is_torch_available()
         else ()
     )
+    all_generative_model_classes = (
+        (XLNetLMHeadModel,) if is_torch_available() else ()
+    )  # TODO (PVP): Check other models whether language generation is also applicable
     test_pruning = False
 
     class XLNetModelTester(object):
@@ -78,6 +81,9 @@ class XLNetModelTest(ModelTesterMixin, unittest.TestCase):
             initializer_range=0.05,
             seed=1,
             type_vocab_size=2,
+            bos_token_id=1,
+            eos_token_id=2,
+            pad_token_id=5,
         ):
             self.parent = parent
             self.batch_size = batch_size
@@ -101,6 +107,9 @@ class XLNetModelTest(ModelTesterMixin, unittest.TestCase):
             self.seed = seed
             self.type_vocab_size = type_vocab_size
             self.type_sequence_label_size = type_sequence_label_size
+            self.bos_token_id = bos_token_id
+            self.pad_token_id = pad_token_id
+            self.eos_token_id = eos_token_id
 
         def prepare_config_and_inputs(self):
             input_ids_1 = ids_tensor([self.batch_size, self.seq_length], self.vocab_size)
@@ -142,6 +151,9 @@ class XLNetModelTest(ModelTesterMixin, unittest.TestCase):
                 bi_data=self.bi_data,
                 initializer_range=self.initializer_range,
                 num_labels=self.type_sequence_label_size,
+                bos_token_id=self.bos_token_id,
+                pad_token_id=self.pad_token_id,
+                eos_token_id=self.eos_token_id,
             )
 
             return (