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from __future__ import annotations
import gc
import logging
import shutil
from pathlib import Path
from typing import Dict, List, Union
import faiss
import numpy as np
import torch
from datasets import Dataset
from faiss.contrib.ondisk import merge_ondisk
from huggingface_hub import snapshot_download
from sentence_transformers import SentenceTransformer
from tqdm import auto as tqdm
logger = logging.getLogger(__name__)
class OnDiskIVFHelper:
def __init__(self, path: Union[str, Path]):
self.path = path
@property
def path(self):
return self._path
@path.setter
def path(self, value: Union[str, Path]):
value = Path(value)
value.mkdir(parents=True, exist_ok=True)
self._path = value
def train(self, xt: np.ndarray):
index = faiss.index_factory(xt.shape[1], "IVF4096,Flat")
logger.info("Training index...")
index.train(xt)
train_index_path = str(self.path / "faiss.index")
logger.info(f"Write {train_index_path}")
faiss.write_index(index, train_index_path)
def add_with_ids(self, xb: np.ndarray, ix: np.ndarray | int):
if isinstance(ix, int):
ix = np.arange(ix, ix + xb.shape[0])
block_num = ix[0]
train_index_path = str(self.path / "faiss.index")
index = faiss.read_index(train_index_path)
logger.info("Adding vectors to index...")
index.add_with_ids(xb, ix)
block_index_path = str(self.path / f"block_{block_num}.index")
logger.info(f"Write {block_index_path}")
faiss.write_index(index, block_index_path)
def merge(self):
logger.info("Loading trained index")
train_index_path = str(self.path / "faiss.index")
index = faiss.read_index(train_index_path)
block_fnames = [str(p) for p in self.path.glob("block_*.index")]
if len(block_fnames) == 0:
return
merged_index_path = str(self.path / "merged_index.ivfdata")
merge_ondisk(index, block_fnames, merged_index_path)
populated_index_path = str(self.path / "populated.index")
logger.info(f"Write {populated_index_path}")
faiss.write_index(index, populated_index_path)
def search(self, xq: np.ndarray, top_k: int = 5, nprobe: int = 16):
populated_index_path = str(self.path / "populated.index")
logger.info("Read " + populated_index_path)
index = faiss.read_index(populated_index_path)
index.nprobe = nprobe
D, I = index.search(xq, top_k) # noqa: E741
return D, I
def delete(self):
shutil.rmtree(self.path)
@property
def ntotal(self) -> int:
populated_index_path = str(self.path / "populated.index")
logger.info("Read " + populated_index_path)
index = faiss.read_index(populated_index_path)
return index.ntotal
def __len__(self) -> int:
return self.ntotal
@property
def is_trained(self) -> bool:
index_file_path = self.path / "populated.index"
if not index_file_path.exists():
return False
index_file_path = str(index_file_path)
index = faiss.read_index(index_file_path)
return index.is_trained
class DatasetIndex:
def __init__(self, path: Union[str, Path]):
self._context_embedding_model = None
self._query_embedding_model = None
self.context_model = "facebook-dpr-ctx_encoder-multiset-base"
self.query_model = "facebook-dpr-question_encoder-multiset-base"
# Ensure we're using CPU
if (
hasattr(torch.backends, "mps")
and torch.backends.mps.is_available()
):
self.device = torch.device("mps")
elif torch.cuda.is_available():
self.device = torch.device("cuda")
else:
self.device = torch.device("cpu")
self.index = OnDiskIVFHelper(path)
@property
def context_embedding_model(self) -> SentenceTransformer:
if self._context_embedding_model is None:
self._query_embedding_model = None
self._context_embedding_model = SentenceTransformer(
self.context_model, device=self.device
)
return self._context_embedding_model
@property
def query_embedding_model(self) -> SentenceTransformer:
if self._query_embedding_model is None:
self._context_embedding_model = None
self._query_embedding_model = SentenceTransformer(
self.query_model, device=self.device
)
return self._query_embedding_model
@property
def ntotal(self) -> int:
try:
ntotal = len(self.index)
except Exception:
try:
self.index.merge()
ntotal = len(self.index)
except Exception:
ntotal = 0
return ntotal
def create_index(
self,
dataset: Dataset | List[Dict] | List[str],
/,
*,
column: str | None = None,
batch_size: int = 32,
block_size: int = 159744,
force: bool = False,
):
"""Build FAISS index for the given documents"""
n_documents = len(dataset)
n_index = self.ntotal
if not force and n_index == n_documents:
logging.info("Found existing index. Skipping...")
return
self.index.delete()
logging.info("Training index/Adding vectors to index...")
# Add vectors to index
for block_start in tqdm.trange(
0, n_documents, block_size, desc="Blocks"
):
# logging.info(f"Starting encoding of {n_documents} documents...")
# Train index
embeddings = self.context_embedding_model.encode(
(
dataset[block_start : block_start + block_size]
if column is None
else dataset[block_start : block_start + block_size][
column
]
),
batch_size=batch_size,
convert_to_numpy=True,
show_progress_bar=True,
device=self.device,
)
batch_end = min(block_start + block_size, n_documents)
assert len(embeddings) == batch_end - block_start
if block_start == 0:
self.index.train(embeddings)
self.index.add_with_ids(embeddings, block_start)
self.index.merge()
print("Number of indexed documents:", len(self.index))
# Clear memory
del embeddings
gc.collect()
if self.device.type == "cuda":
torch.cuda.empty_cache()
logging.info("Indexing complete!")
def search(self, query: str, k: int = 5) -> List[Dict]:
"""Search the index for similar documents"""
if self.index is None:
raise ValueError("Index not built yet!")
# Encode query
if isinstance(query, str):
query = [query]
query_vector = self.query_embedding_model.encode(
query, convert_to_numpy=True
)
# Search
D, I = self.index.search(query_vector, k) # noqa: E741
# Format results
results = []
for i in range(len(query)):
results.append([
(idx, score) for idx, score in zip(I[i], D[i]) if idx >= 0
])
return results
@classmethod
def from_pretrained(cls, model_id: str) -> DatasetIndex:
"""Download and load a pre-trained index"""
snapshot_path = snapshot_download(
repo_id=model_id,
repo_type="dataset",
allow_patterns="index/*",
)
snapshot_path = Path(snapshot_path)
self = cls(snapshot_path / "index")
# make sure the index is merged
_ = self.ntotal
return self
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