community[minor]: Add Ascend NPU optimized Embeddings (#20260)

- **Description:** Add NPU support for embeddings

---------

Co-authored-by: Bagatur <22008038+baskaryan@users.noreply.github.com>
Co-authored-by: Bagatur <baskaryan@gmail.com>

libs/community/langchain_community/embeddings/ascend.py

@@ -0,0 +1,120 @@
+import os
+from typing import Any, Dict, List, Optional
+
+from langchain_core.embeddings import Embeddings
+from langchain_core.pydantic_v1 import BaseModel, root_validator
+
+
+class AscendEmbeddings(Embeddings, BaseModel):
+    """
+    Ascend NPU accelerate Embedding model
+
+    Please ensure that you have installed CANN and torch_npu.
+
+    Example:
+
+    from langchain_community.embeddings import AscendEmbeddings
+    model = AscendEmbeddings(model_path=<path_to_model>,
+        device_id=0,
+        query_instruction="Represent this sentence for searching relevant passages: "
+    )
+    """
+
+    """model path"""
+    model_path: str
+    """Ascend NPU device id."""
+    device_id: int = 0
+    """Unstruntion to used for embedding query."""
+    query_instruction: str = ""
+    """Unstruntion to used for embedding document."""
+    document_instruction: str = ""
+    use_fp16: bool = True
+    pooling_method: Optional[str] = "cls"
+    model: Any
+    tokenizer: Any
+
+    def __init__(self, *args: Any, **kwargs: Any) -> None:
+        super().__init__(*args, **kwargs)
+        try:
+            from transformers import AutoModel, AutoTokenizer
+        except ImportError as e:
+            raise ImportError(
+                "Unable to import transformers, please install with "
+                "`pip install -U transformers`."
+            ) from e
+        try:
+            self.model = AutoModel.from_pretrained(self.model_path).npu().eval()
+            self.tokenizer = AutoTokenizer.from_pretrained(self.model_path)
+        except Exception as e:
+            raise Exception(
+                f"Failed to load model [self.model_path], due to following error:{e}"
+            )
+
+        if self.use_fp16:
+            self.model.half()
+        self.encode([f"warmup {i} times" for i in range(10)])
+
+    @root_validator
+    def validate_environment(cls, values: Dict) -> Dict:
+        if not os.access(values["model_path"], os.F_OK):
+            raise FileNotFoundError(
+                f"Unabled to find valid model path in [{values['model_path']}]"
+            )
+        try:
+            import torch_npu
+        except ImportError:
+            raise ModuleNotFoundError("torch_npu not found, please install torch_npu")
+        except Exception as e:
+            raise e
+        try:
+            torch_npu.npu.set_device(values["device_id"])
+        except Exception as e:
+            raise Exception(f"set device failed due to {e}")
+        return values
+
+    def encode(self, sentences: Any) -> Any:
+        inputs = self.tokenizer(
+            sentences,
+            padding=True,
+            truncation=True,
+            return_tensors="pt",
+            max_length=512,
+        )
+        try:
+            import torch
+        except ImportError as e:
+            raise ImportError(
+                "Unable to import torch, please install with " "`pip install -U torch`."
+            ) from e
+        last_hidden_state = self.model(
+            inputs.input_ids.npu(), inputs.attention_mask.npu(), return_dict=True
+        ).last_hidden_state
+        tmp = self.pooling(last_hidden_state, inputs["attention_mask"].npu())
+        embeddings = torch.nn.functional.normalize(tmp, dim=-1)
+        return embeddings.cpu().detach().numpy()
+
+    def pooling(self, last_hidden_state: Any, attention_mask: Any = None) -> Any:
+        try:
+            import torch
+        except ImportError as e:
+            raise ImportError(
+                "Unable to import torch, please install with " "`pip install -U torch`."
+            ) from e
+        if self.pooling_method == "cls":
+            return last_hidden_state[:, 0]
+        elif self.pooling_method == "mean":
+            s = torch.sum(
+                last_hidden_state * attention_mask.unsqueeze(-1).float(), dim=-1
+            )
+            d = attention_mask.sum(dim=1, keepdim=True).float()
+            return s / d
+        else:
+            raise NotImplementedError(
+                f"Pooling method [{self.pooling_method}] not implemented"
+            )
+
+    def embed_documents(self, texts: List[str]) -> List[List[float]]:
+        return self.encode([self.document_instruction + text for text in texts])
+
+    def embed_query(self, text: str) -> List[float]:
+        return self.encode([self.query_instruction + text])[0]