Attention sparse embeddings (#235)

* WIP: sparse embeddings using attention

* support for stopwords

* apply stopwords

* proceed implementation of sparse attention embeddings (#234)

* complete inference

* query embed + comment

* use simpler weights formula instead of sorting of words

* update tests

* fix: fix bm42 usage, add query_embed to SparseTextEmbedding, update tests

---------

Co-authored-by: George <[email protected]>

fastembed/common/onnx_model.py

@@ -1,3 +1,4 @@
+from dataclasses import dataclass
 from pathlib import Path
 from typing import Any, Dict, Generic, Iterable, Optional, Tuple, Type, TypeVar, Sequence
 import warnings
@@ -13,13 +14,19 @@
 T = TypeVar("T")
 
 
+@dataclass
+class OnnxOutputContext:
+    model_output: np.ndarray
+    attention_mask: Optional[np.ndarray] = None
+    input_ids: Optional[np.ndarray] = None
+
+
 class OnnxModel(Generic[T]):
     @classmethod
     def _get_worker_class(cls) -> Type["EmbeddingWorker"]:
         raise NotImplementedError("Subclasses must implement this method")
 
-    @classmethod
-    def _post_process_onnx_output(cls, output: Tuple[np.ndarray, np.ndarray]) -> Iterable[T]:
+    def _post_process_onnx_output(self, output: OnnxOutputContext) -> Iterable[T]:
         raise NotImplementedError("Subclasses must implement this method")
 
     def __init__(self) -> None:
@@ -74,7 +81,7 @@ def load_onnx_model(
                     RuntimeWarning,
                 )
 
-    def onnx_embed(self, *args, **kwargs) -> Tuple[np.ndarray, np.ndarray]:
+    def onnx_embed(self, *args, **kwargs) -> OnnxOutputContext:
         raise NotImplementedError("Subclasses must implement this method")
 
 

fastembed/common/preprocessor_utils.py

@@ -1,12 +1,24 @@
 import json
 from pathlib import Path
+from typing import Tuple
 
 from tokenizers import Tokenizer, AddedToken
 
 from fastembed.image.transform.operators import Compose
 
 
-def load_tokenizer(model_dir: Path, max_length: int = 512) -> Tokenizer:
+def load_special_tokens(model_dir: Path) -> dict:
+    tokens_map_path = model_dir / "special_tokens_map.json"
+    if not tokens_map_path.exists():
+        raise ValueError(f"Could not find special_tokens_map.json in {model_dir}")
+
+    with open(str(tokens_map_path)) as tokens_map_file:
+        tokens_map = json.load(tokens_map_file)
+
+    return tokens_map
+
+
+def load_tokenizer(model_dir: Path, max_length: int = 512) -> Tuple[Tokenizer, dict]:
     config_path = model_dir / "config.json"
     if not config_path.exists():
         raise ValueError(f"Could not find config.json in {model_dir}")
@@ -19,18 +31,13 @@ def load_tokenizer(model_dir: Path, max_length: int = 512) -> Tokenizer:
     if not tokenizer_config_path.exists():
         raise ValueError(f"Could not find tokenizer_config.json in {model_dir}")
 
-    tokens_map_path = model_dir / "special_tokens_map.json"
-    if not tokens_map_path.exists():
-        raise ValueError(f"Could not find special_tokens_map.json in {model_dir}")
-
     with open(str(config_path)) as config_file:
         config = json.load(config_file)
 
     with open(str(tokenizer_config_path)) as tokenizer_config_file:
         tokenizer_config = json.load(tokenizer_config_file)
 
-    with open(str(tokens_map_path)) as tokens_map_file:
-        tokens_map = json.load(tokens_map_file)
+    tokens_map = load_special_tokens(model_dir)
 
     tokenizer = Tokenizer.from_file(str(tokenizer_path))
     tokenizer.enable_truncation(max_length=min(tokenizer_config["model_max_length"], max_length))
@@ -44,7 +51,16 @@ def load_tokenizer(model_dir: Path, max_length: int = 512) -> Tokenizer:
         elif isinstance(token, dict):
             tokenizer.add_special_tokens([AddedToken(**token)])
 
-    return tokenizer
+    special_token_to_id = {}
+
+    for token in tokens_map.values():
+        if isinstance(token, str):
+            special_token_to_id[token] = tokenizer.token_to_id(token)
+        elif isinstance(token, dict):
+            token_str = token.get("content", "")
+            special_token_to_id[token_str] = tokenizer.token_to_id(token_str)
+
+    return tokenizer, special_token_to_id
 
 
 def load_preprocessor(model_dir: Path) -> Compose:

fastembed/image/onnx_embedding.py

@@ -2,6 +2,7 @@
 
 import numpy as np
 
+from fastembed.common.onnx_model import OnnxOutputContext
 from fastembed.common.utils import normalize, define_cache_dir
 from fastembed.common import ImageInput, OnnxProvider
 from fastembed.image.image_embedding_base import ImageEmbeddingBase
@@ -108,9 +109,8 @@ def _preprocess_onnx_input(self, onnx_input: Dict[str, np.ndarray]) -> Dict[str,
 
         return onnx_input
 
-    @classmethod
-    def _post_process_onnx_output(cls, output: np.ndarray) -> Iterable[np.ndarray]:
-        return normalize(output).astype(np.float32)
+    def _post_process_onnx_output(self, output: OnnxOutputContext) -> Iterable[np.ndarray]:
+        return normalize(output.model_output).astype(np.float32)
 
 
 class OnnxImageEmbeddingWorker(ImageEmbeddingWorker):

fastembed/image/onnx_image_model.py

@@ -8,7 +8,7 @@
 import numpy as np
 
 from fastembed.common.preprocessor_utils import load_preprocessor
-from fastembed.common.onnx_model import OnnxModel, EmbeddingWorker, T
+from fastembed.common.onnx_model import OnnxModel, EmbeddingWorker, T, OnnxOutputContext
 from fastembed.common import PathInput, ImageInput, OnnxProvider
 from fastembed.common.utils import iter_batch
 from fastembed.parallel_processor import ParallelWorkerPool
@@ -21,8 +21,7 @@ class OnnxImageModel(OnnxModel[T]):
     def _get_worker_class(cls) -> Type["ImageEmbeddingWorker"]:
         raise NotImplementedError("Subclasses must implement this method")
 
-    @classmethod
-    def _post_process_onnx_output(cls, output: np.ndarray) -> Iterable[T]:
+    def _post_process_onnx_output(self, output: OnnxOutputContext) -> Iterable[T]:
         raise NotImplementedError("Subclasses must implement this method")
 
     def __init__(self) -> None:
@@ -47,7 +46,7 @@ def load_onnx_model(
         )
         self.processor = load_preprocessor(model_dir=model_dir)
 
-    def onnx_embed(self, images: List[PathInput]) -> np.ndarray:
+    def onnx_embed(self, images: List[PathInput]) -> OnnxOutputContext:
         with contextlib.ExitStack():
             image_files = [Image.open(image) for image in images]
             encoded = self.processor(image_files)
@@ -56,7 +55,9 @@ def onnx_embed(self, images: List[PathInput]) -> np.ndarray:
 
         model_output = self.model.run(None, onnx_input)
         embeddings = model_output[0]
-        return embeddings
+        return OnnxOutputContext(
+            model_output=embeddings
+        )
 
     def _embed_images(
         self,