merge conflicts - renamed to previous_token singular

src/transformers/modeling_utils.py

@@ -556,46 +556,81 @@ class PreTrainedModel(nn.Module):
         length_penalty=None,
         num_return_sequences=None,
     ):
-        """ Sequence generator for models with a LM head.
-
-        The method currently supports greedy or penalized greedy decoding, sampling with top-k or nucleus sampling
+        r""" Generates sequences for models with a LM head. The method currently supports greedy or penalized greedy decoding, sampling with top-k or nucleus sampling
         and beam-search.
 
-        Adapted in part from Facebook's XLM beam search code: https://github.com/facebookresearch/XLM
+        Adapted in part from `Facebook's XLM beam search code`_.
+
+        .. _`Facebook's XLM beam search code`:
+           https://github.com/facebookresearch/XLM/blob/9e6f6814d17be4fe5b15f2e6c43eb2b2d76daeb4/src/model/transformer.py#L529
+
+
+        Parameters:
 
-        Params:
-            **input_ids**: (`optional`) `torch.LongTensor` of shape (1, sequence_length)
+            input_ids: (`optional`) `torch.LongTensor` of shape `(batch_size, sequence_length)`
                 The sequence used as a prompt for the generation. If `None` the method initializes
-                it as an empty `torch.LongTensor` of shape (1,)
-            **max_length**: (`optional`) int
+                it as an empty `torch.LongTensor` of shape `(1,)`.
+
+            max_length: (`optional`) int
                 The max length of the sequence to be generated.  Between 1 and infinity. Default to 20.
-            **do_sample**: (`optional`) bool
-                If set to `False` we use greedy decoding; otherwise sampling. Default to greedy sampling.
-            **num_beams**: (`optional`) int
-                Number of beams for beam search. 1 means no beam serach. Default to 1.
-            **temperature**: (`optional`) float
-                The value used to module the next token probabilities.
-            **top_k**: (`optional`) int
+
+            do_sample: (`optional`) bool
+                If set to `False` greedy decoding is used. Otherwise sampling is used. Default to greedy sampling.
+
+            num_beams: (`optional`) int
+                Number of beams for beam search. Must be between 1 and infinity. 1 means no beam search. Default to 1.
+
+            temperature: (`optional`) float
+                The value used to module the next token probabilities. Must be strictely positive. Default to 1.0.
+
+            top_k: (`optional`) int
                 The number of highest probability vocabulary tokens to keep for top-k-filtering. Between 1 and infinity. Default to 50.
-            **top_p**: (`optional`) float
+
+            top_p: (`optional`) float
                 The cumulative probability of parameter highest probability vocabulary tokens to keep for nucleus sampling. Must be between 0 and 1. Default to 1.
-            **repetition_penalty**: (`optional`) float
-                The parameter for repetition penalty. Between 1.0 and + infinity. 1.0 means no penalty. Default to 1.
-            **bos_token_id**: (`optional`) int
+
+            repetition_penalty: (`optional`) float
+                The parameter for repetition penalty. Between 1.0 and infinity. 1.0 means no penalty. Default to 1.0.
+
+            bos_token_id: (`optional`) int
                 Beginning of sentence token if no prompt is provided. Default to 0.
-            **eos_token_ids**: (`optional`) int or list of int
+
+            eos_token_ids: (`optional`) int or list of int
                 End of sequence token or list of tokens to stop the generation. Default to 0.
-            **length_penalty**: (`optional`) float
+            length_penalty: (`optional`) float
                 Exponential penalty to the length. Default to 1.
-            **num_return_sequences**: (`optional`) int
-                The number of independantly computed returned sequences for each element in the batch. Default to 1.
+
+            num_return_sequences: (`optional`) int
+                The number of independently computed returned sequences for each element in the batch. Default to 1.
+
+        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
+            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)  # generate 3 independent sequences using beam search decoding (5 beams) 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)))
+
+            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, do_sample=True, temperature=0.7, bos_token_id=tokenizer.bos_token_id, eos_token_ids=tokenizer.eos_token_id, num_beams=3)  # generate sequences using beam search decoding (3 beams)
+            print('Generated: {}'.format(tokenizer.decode(outputs[0], skip_special_tokens=True)))
         """
 
         # We cannot generate if the model does not have a LM head
         if self.get_output_embeddings() is None:
             raise AttributeError(
                 "You tried to generate sequences with a model that does not have a LM Head."
-                "Please use another model class (e.g. `OpenAIGPTLMHeadModel`)"
+                "Please use another model class (e.g. `OpenAIGPTLMHeadModel`, `XLNetLMHeadModel`, `GPT2LMHeadModel`, `CTRLLMHeadModel`, `T5WithLMHeadModel`, `TransfoXLLMHeadModel`)"
             )
 
         max_length = max_length if max_length is not None else self.config.max_length
@@ -623,7 +658,7 @@ class PreTrainedModel(nn.Module):
         assert isinstance(max_length, int) and max_length > 0, "`max_length` should be a strictely positive integer."
         assert isinstance(do_sample, bool), "`do_sample` should be a boolean."
         assert isinstance(num_beams, int) and num_beams > 0, "`num_beams` should be a strictely positive integer."
-        # assert temperature >= 0, "`temperature` should be positive."
+        assert temperature > 0, "`temperature` should be strictely positive."
         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."
@@ -725,16 +760,16 @@ class PreTrainedModel(nn.Module):
             # repetition penalty from CTRL paper (https://arxiv.org/abs/1909.05858)
             if repetition_penalty != 1.0:
                 for i in range(batch_size):
-                    for previous_tokens in set(input_ids[i].tolist()):
+                    for previous_token in set(input_ids[i].tolist()):
                         # if score < 0 then repetition penalty has to multiplied to reduce the previous token probability
-                        if next_token_logits[i, previous_tokens] < 0:
-                            next_token_logits[i, previous_tokens] *= repetition_penalty
+                        if next_token_logits[i, previous_token] < 0:
+                            next_token_logits[i, previous_token] *= repetition_penalty
                         else:
-                            next_token_logits[i, previous_tokens] /= repetition_penalty
+                            next_token_logits[i, previous_token] /= repetition_penalty
 
             if do_sample:
                 # Temperature (higher temperature => more likely to sample low probability tokens)
-                if temperature > 0 and temperature != 1.0:
+                if temperature != 1.0:
                     next_token_logits = next_token_logits / temperature
                 # Top-p/top-k filtering
                 next_token_logits = top_k_top_p_filtering(next_token_logits, top_k=top_k, top_p=top_p)
@@ -808,16 +843,16 @@ class PreTrainedModel(nn.Module):
             # repetition penalty (from CTRL paper https://arxiv.org/abs/1909.05858)
             if repetition_penalty != 1.0:
                 for i in range(batch_size * num_beams):
-                    for previous_tokens in set(input_ids[i].tolist()):
+                    for previous_token in set(input_ids[i].tolist()):
                         # if score < 0 then repetition penalty has to multiplied to reduce the previous token probability
-                        if scores[i, previous_tokens] < 0:
-                            scores[i, previous_tokens] *= repetition_penalty
+                        if scores[i, previous_token] < 0:
+                            scores[i, previous_token] *= repetition_penalty
                         else:
-                            scores[i, previous_tokens] /= repetition_penalty
+                            scores[i, previous_token] /= repetition_penalty
 
             if do_sample:
                 # Temperature (higher temperature => more likely to sample low probability tokens)
-                if temperature > 0 and temperature != 1.0:
+                if temperature != 1.0:
                     scores = scores / temperature
                 # Top-p/top-k filtering
                 scores = top_k_top_p_filtering(