CoCa: generate and beam search

README.md

@@ -285,6 +285,32 @@ Training [CoCa](https://arxiv.org/abs/2205.01917) models is enabled through spec
 ```
 Credit to [lucidrains](https://github.com/lucidrains) for [initial code](https://github.com/lucidrains/CoCa-pytorch), [gpucce](https://github.com/gpucce) for adapting the code to open_clip, and [iejMac](https://github.com/iejMac) for training the models.
 
+### Generating text with CoCa
+
+To generate text with coca this should work
+
+```python
+import open_clip
+from PIL import Image
+
+model, _, transform = open_clip.create_model_and_transform(
+  model_name="coca_ViT-B-32",
+  pretrained="path/to/pretrained"
+)
+
+# load an image
+im = Image.load("path/to/image").convert("RGB")
+# transform the image and add a batch size dimension
+im = transform(im).unsqueeze(0)
+
+generated = model.generate(im)
+# alternatively if computation was running on a gpu
+# generated = generated.detach()
+
+print(open_clip.decode(generated[0]))
+# "<start_of_text> some text here <end_of_text>"
+```
+
 ### Training with pre-trained language models as text encoder:
 
 If you wish to use different language models as the text encoder for CLIP you can do so by using one of the Hugging Face model configs in ```src/open_clip/model_configs``` and passing in it's tokenizer as the ```--model``` and ```--hf-tokenizer-name``` parameters respectively. Currently we only support RoBERTa ("test-roberta" config), however adding new models should be trivial. You can also determine how many layers, from the end, to leave unfrozen with the ```--lock-text-unlocked-layers``` parameter. Here's an example command to train CLIP with the RoBERTa LM that has it's last 10 layers unfrozen:

src/open_clip/__init__.py

@@ -8,5 +8,5 @@
 from .openai import load_openai_model, list_openai_models
 from .pretrained import list_pretrained, list_pretrained_models_by_tag, list_pretrained_tags_by_model,\
     get_pretrained_url, download_pretrained_from_url, is_pretrained_cfg, get_pretrained_cfg, download_pretrained
-from .tokenizer import SimpleTokenizer, tokenize
+from .tokenizer import SimpleTokenizer, tokenize, decode
 from .transform import image_transform, AugmentationCfg

src/open_clip/coca_model.py

@@ -13,8 +13,15 @@
     MultimodalTransformer,
 )
 from .model import CLIPTextCfg, CLIPVisionCfg, _build_vision_tower, _build_text_tower
-from .generation_utils import top_a, top_k, top_p
+from .generation_utils import top_a, top_k, top_p, prepare_inputs_for_generation
+from transformers import BeamSearchScorer, LogitsProcessorList, MinLengthLogitsProcessor, StoppingCriteriaList, MaxLengthCriteria
 
+GENERATION_TYPES = {
+    "top_k": top_k,
+    "top_p": top_p,
+    "top_a": top_a,
+    "beam_search": "beam_search"
+}
 
 @dataclass
 class MultimodalCfg(CLIPTextCfg):
@@ -108,8 +115,8 @@ def _encode_image(self, images, normalize=True):
         image_latent = F.normalize(image_latent, dim=-1) if normalize else image_latent
         return image_latent, tokens_embs
 
-    def _encode_text(self, text, normalize=True):
-        text = text[:, :-1]  # make space for CLS token
+    def _encode_text(self, text, normalize=True, embed_cls=True):
+        text = text[:, :-1] if embed_cls else text # make space for CLS token
         text_latent, token_emb = self.text(text)
         text_latent = F.normalize(text_latent, dim=-1) if normalize else text_latent
         return text_latent, token_emb
@@ -118,13 +125,14 @@ def encode_image(self, images, normalize=True):
         image_latent, _ = self._encode_image(images, normalize=normalize)
         return image_latent
 
-    def encode_text(self, text, normalize=True):
-        text_latent, _ = self._encode_text(text, normalize=normalize)
+    def encode_text(self, text, normalize=True, embed_cls=True):
+        text_latent, _ = self._encode_text(text, normalize=normalize, embed_cls=embed_cls)
         return text_latent
 
-    def forward(self, image, text):
-        text_latent, token_embs = self._encode_text(text)
-        image_latent, image_embs = self._encode_image(image)
+    def forward(self, image, text, embed_cls=True, image_latent=None, image_embs=None):
+        text_latent, token_embs = self._encode_text(text, embed_cls=embed_cls)
+        if image_latent is None or image_embs is None:
+            image_latent, image_embs = self._encode_image(image)
 
         # TODO: add assertion to avoid bugs?
         labels = text[:, -token_embs.shape[1]:]
@@ -141,19 +149,47 @@ def forward(self, image, text):
     def generate(
             self,
             image,
-            text,
-            seq_len,
+            text=None,
+            seq_len=77,
             max_seq_len=77,
             mask_prob=0.0,
             temperature=1.,
-            filter_logits_fn=top_k,
+            generation_type="beam_search",
             filter_thres=0.9,
             min_p_pow=2.0,
             min_p_ratio=0.02,
+            pad_token_id=None,
+            eos_token_id=None,
+            sot_token_id=None,
+            num_beams=6,
+            num_beam_groups=3,
+            min_seq_len=5,
+            stopping_criteria=None,
     ):
 
+        assert generation_type in GENERATION_TYPES, \
+            f"generation_type has to be one of {'| ' + ' | '.join(list(GENERATION_TYPES.keys())) + ' |'}."
+        filter_logits_fn = GENERATION_TYPES[generation_type]
+
+        if generation_type == "beam_search":
+            return self.generate_beamsearch(
+                image_inputs = image,
+                max_length = seq_len,
+                pad_token_id=pad_token_id,
+                eos_token_id=eos_token_id,
+                sot_token_id=sot_token_id,
+                num_beams=num_beams,
+                num_beam_groups=num_beam_groups,
+                min_seq_len=min_seq_len,
+                stopping_criteria=stopping_criteria,
+            )
+
         assert mask_prob < 1, "mask_prob must be smaller than 1."
+        device = image.device
 
+        sot_token_id = 49406 if sot_token_id is None else sot_token_id
+        if text is None:
+            text = torch.ones((image.shape[0], 1), device=device, dtype=torch.long) * sot_token_id
         was_training = self.training
         num_dims = len(text.shape)
 
@@ -167,8 +203,7 @@ def generate(
         for _ in range(seq_len):
             x = out[:, -max_seq_len:]
 
-            # TODO: adjust for dict output
-            logits = self(image, x)["logits"][:, -1]
+            logits = self(image, x, embed_cls=False)["logits"][:, -1]
 
             if filter_logits_fn in {top_k, top_p}:
                 filtered_logits = filter_logits_fn(logits, thres=filter_thres)
@@ -184,10 +219,167 @@ def generate(
 
             out = torch.cat((out, sample), dim=-1)
 
-        out = out[:, t:]
-
         if num_dims == 1:
             out = out.squeeze(0)
 
         self.train(was_training)
         return out
+
+    def generate_beamsearch(
+            self,
+            image_inputs,
+            max_length,
+            pad_token_id=None,
+            eos_token_id=None,
+            sot_token_id=None,
+            num_beams=6,
+            num_beam_groups=3,
+            min_seq_len=5,
+            stopping_criteria=None,
+        ):
+
+        sot_token_id = 49406 if sot_token_id is None else sot_token_id
+        eos_token_id = 49407 if eos_token_id is None else eos_token_id
+        pad_token_id = self.pad_id if pad_token_id is None else pad_token_id
+
+        device = image_inputs.device
+        batch_size = image_inputs.shape[0]
+        image_inputs = torch.repeat_interleave(image_inputs, num_beams, dim=0)
+        image_latent, image_embs = self._encode_image(image_inputs)
+
+        input_ids = torch.ones((batch_size * num_beams, 1), device=device, dtype=torch.long)
+        input_ids = input_ids * sot_token_id
+        beam_scorer = BeamSearchScorer(
+            batch_size=batch_size,
+            num_beams=num_beams,
+            device=device,
+            num_beam_groups=num_beam_groups,
+        )
+        # instantiate logits processors
+        target_logits_processor_list = [
+            MinLengthLogitsProcessor(min_seq_len, eos_token_id=eos_token_id)
+        ]
+        logits_processor = LogitsProcessorList(
+            target_logits_processor_list
+        )
+        if stopping_criteria is None:
+            stopping_criteria = [MaxLengthCriteria(max_length=max_length)]
+        stopping_criteria = StoppingCriteriaList(
+            stopping_criteria
+        )
+
+        batch_size = len(beam_scorer._beam_hyps)
+        num_beams = beam_scorer.num_beams
+        num_beam_groups = beam_scorer.num_beam_groups
+        num_sub_beams = num_beams // num_beam_groups
+        batch_beam_size, cur_len = input_ids.shape
+        beam_indices = None
+
+        if num_beams * batch_size != batch_beam_size:
+            raise ValueError(
+                f"Batch dimension of `input_ids` should be {num_beams * batch_size}, but is {batch_beam_size}."
+            )
+
+        beam_scores = torch.full((batch_size, num_beams), -1e9, dtype=torch.float, device=device)
+        # initialise score of first beam of each group with 0 and the rest with 1e-9. This ensures that the beams in
+        # the same group don't produce same tokens everytime.
+        beam_scores[:, ::num_sub_beams] = 0
+        beam_scores = beam_scores.view((batch_size * num_beams,))
+
+        while True:
+
+            # predicted tokens in cur_len step
+            current_tokens = torch.zeros(batch_size * num_beams, dtype=input_ids.dtype, device=device)
+
+            # indices which will form the beams in the next time step
+            reordering_indices = torch.zeros(batch_size * num_beams, dtype=torch.long, device=device)
+
+            # do one decoder step on all beams of all sentences in batch
+            model_inputs = prepare_inputs_for_generation(input_ids=input_ids, image_inputs=image_inputs)
+            outputs = self(
+                model_inputs['images'],
+                model_inputs['text'],
+                embed_cls=False,
+                image_latent=image_latent,
+                image_embs=image_embs
+            )
+
+            for beam_group_idx in range(num_beam_groups):
+                group_start_idx = beam_group_idx * num_sub_beams
+                group_end_idx = min(group_start_idx + num_sub_beams, num_beams)
+                group_size = group_end_idx - group_start_idx
+
+                # indices of beams of current group among all sentences in batch
+                batch_group_indices = []
+
+                for batch_idx in range(batch_size):
+                    batch_group_indices.extend(
+                        [batch_idx * num_beams + idx for idx in range(group_start_idx, group_end_idx)]
+                    )
+                group_input_ids = input_ids[batch_group_indices]
+
+                # select outputs of beams of currentg group only
+                next_token_logits = outputs['logits'][batch_group_indices, -1, :]
+                vocab_size = next_token_logits.shape[-1]
+
+                next_token_scores_processed = logits_processor(
+                    group_input_ids, next_token_logits, current_tokens=current_tokens, beam_group_idx=beam_group_idx
+                )
+                next_token_scores = next_token_scores_processed + beam_scores[batch_group_indices].unsqueeze(-1)
+                next_token_scores = next_token_scores.expand_as(next_token_scores_processed)
+
+                # reshape for beam search
+                next_token_scores = next_token_scores.view(batch_size, group_size * vocab_size)
+
+                next_token_scores, next_tokens = torch.topk(
+                    next_token_scores, 2 * group_size, dim=1, largest=True, sorted=True
+                )
+
+                next_indices = torch.div(next_tokens, vocab_size, rounding_mode="floor")
+                next_tokens = next_tokens % vocab_size
+
+                # stateless
+                process_beam_indices = sum(beam_indices, ()) if beam_indices is not None else None
+                beam_outputs = beam_scorer.process(
+                    group_input_ids,
+                    next_token_scores,
+                    next_tokens,
+                    next_indices,
+                    pad_token_id=pad_token_id,
+                    eos_token_id=eos_token_id,
+                    beam_indices=process_beam_indices,
+                )
+                beam_scores[batch_group_indices] = beam_outputs["next_beam_scores"]
+                beam_next_tokens = beam_outputs["next_beam_tokens"]
+                beam_idx = beam_outputs["next_beam_indices"]
+
+                input_ids[batch_group_indices] = group_input_ids[beam_idx]
+                group_input_ids = torch.cat([group_input_ids[beam_idx, :], beam_next_tokens.unsqueeze(-1)], dim=-1)
+                current_tokens[batch_group_indices] = group_input_ids[:, -1]
+
+                # (beam_idx // group_size) -> batch_idx
+                # (beam_idx % group_size) -> offset of idx inside the group
+                reordering_indices[batch_group_indices] = (
+                    num_beams * torch.div(beam_idx, group_size, rounding_mode="floor") + group_start_idx + (beam_idx % group_size)
+                )
+
+            input_ids = torch.cat([input_ids, current_tokens.unsqueeze(-1)], dim=-1)
+
+            # increase cur_len
+            cur_len = cur_len + 1
+            if beam_scorer.is_done or stopping_criteria(input_ids, None):
+                break
+
+        final_beam_indices = sum(beam_indices, ()) if beam_indices is not None else None
+        sequence_outputs = beam_scorer.finalize(
+            input_ids,
+            beam_scores,
+            next_tokens,
+            next_indices,
+            pad_token_id=pad_token_id,
+            eos_token_id=eos_token_id,
+            max_length=stopping_criteria.max_length,
+            beam_indices=final_beam_indices,
+        )
+        return sequence_outputs['sequences']
+

src/open_clip/generation_utils.py

@@ -1,6 +1,5 @@
 from math import ceil
 import torch
-from torch import nn
 import torch.nn.functional as F
 
 
@@ -35,3 +34,25 @@ def top_a(logits, min_p_pow=2.0, min_p_ratio=0.02):
     logits[probs < limit] = float('-inf')
     logits[probs >= limit] = 1
     return logits
+
+
+def prepare_inputs_for_generation(input_ids, image_inputs, past=None, **kwargs):
+    if past:
+        input_ids = input_ids[:, -1].unsqueeze(-1)
+
+    attention_mask = kwargs.get("attention_mask", None)
+    position_ids = kwargs.get("position_ids", None)
+
+    if attention_mask is not None and position_ids is None:
+        # create position_ids on the fly for batch generation
+        position_ids = attention_mask.long().cumsum(-1) - 1
+        position_ids.masked_fill_(attention_mask == 0, 1)
+    else:
+        position_ids = None
+    return {
+        "text": input_ids,
+        "images": image_inputs,
+        "past_key_values": past,
+        "position_ids": position_ids,
+        "attention_mask": attention_mask,
+    }

src/open_clip/tokenizer.py

@@ -152,6 +152,9 @@ def decode(self, tokens):
 
 _tokenizer = SimpleTokenizer()
 
+def decode(output_ids: torch.Tensor):
+    output_ids = output_ids.cpu().numpy()
+    return _tokenizer.decode(output_ids)
 
 def tokenize(texts: Union[str, List[str]], context_length: int = 77) -> torch.LongTensor:
     """