前言
当我们需要对大规模的数据向量化以存到向量数据库中时，且服务器上有多个GPU可以支配，我们希望同时利用所有的GPU来并行这一过程，加速向量化。
代码
就几行代码，不废话了
from sentence_transformers import SentenceTransformer
#Important, you need to shield your code with if __name__. Otherwise, CUDA runs into issues when spawning new processes.
if __name__ == '__main__':
#Create a large list of 100k sentences
sentences = ["This is sentence {}".format(i) for i in range(100000)]
#Define the model
model = SentenceTransformer('all-MiniLM-L6-v2')
#Start the multi-process pool on all available CUDA devices
pool = model.start_multi_process_pool()
#Compute the embeddings using the multi-process pool
emb = model.encode_multi_process(sentences, pool)
print("Embeddings computed. Shape:", emb.shape)
#Optional: Stop the proccesses in the pool
model.stop_multi_process_pool(pool)
注意：一定要加if __name__ == '__main__':这一句，不然报如下错：
RuntimeError:
An attempt has been made to start a new process before the
current process has finished its bootstrapping phase.
This probably means that you are not using fork to start your
child processes and you have forgotten to use the proper idiom
in the main module:
if __name__ == '__main__':
freeze_support()
...
The "freeze_support()" line can be omitted if the program
is not going to be frozen to produce an executable.
其实官方已经给出代码啦，我只不过复制粘贴了一下，代码位置：computing_embeddings_multi_gpu.py
官方还给出了流式encode的例子，也是多GPU并行的，如下：
from sentence_transformers import SentenceTransformer, LoggingHandler
import logging
from datasets import load_dataset
from torch.utils.data import DataLoader
from tqdm import tqdm
logging.basicConfig(format='%(asctime)s - %(message)s',
datefmt='%Y-%m-%d %H:%M:%S',
level=logging.INFO,
handlers=[LoggingHandler()])
#Important, you need to shield your code with if __name__. Otherwise, CUDA runs into issues when spawning new processes.
if __name__ == '__main__':
#Set params
data_stream_size = 16384 #Size of the data that is loaded into memory at once
chunk_size = 1024 #Size of the chunks that are sent to each process
encode_batch_size = 128 #Batch size of the model
#Load a large dataset in streaming mode. more info: https://huggingface.co/docs/datasets/stream
dataset = load_dataset('yahoo_answers_topics', split='train', streaming=True)
dataloader = DataLoader(dataset.with_format("torch"), batch_size=data_stream_size)
#Define the model
model = SentenceTransformer('all-MiniLM-L6-v2')
#Start the multi-process pool on all available CUDA devices
pool = model.start_multi_process_pool()
for i, batch in enumerate(tqdm(dataloader)):
#Compute the embeddings using the multi-process pool
sentences = batch['best_answer']
batch_emb = model.encode_multi_process(sentences, pool, chunk_size=chunk_size, batch_size=encode_batch_size)
print("Embeddings computed for 1 batch. Shape:", batch_emb.shape)
#Optional: Stop the proccesses in the pool
model.stop_multi_process_pool(pool)
官方案例：computing_embeddings_streaming.py
+-----------------------------------------------------------------------------+
| NVIDIA-SMI 515.105.01 Driver Version: 515.105.01 CUDA Version: 11.7 |
|-------------------------------+----------------------+----------------------+
| GPU Name Persistence-M| Bus-Id Disp.A | Volatile Uncorr. ECC |
| Fan Temp Perf Pwr:Usage/Cap| Memory-Usage | GPU-Util Compute M. |
| | | MIG M. |
|===============================+======================+======================|
| 0 NVIDIA A800-SXM... On | 00000000:23:00.0 Off | 0 |
| N/A 58C P0 297W / 400W | 75340MiB / 81920MiB | 100% Default |
| | | Disabled |
+-------------------------------+----------------------+----------------------+
| 1 NVIDIA A800-SXM... On | 00000000:29:00.0 Off | 0 |
| N/A 71C P0 352W / 400W | 80672MiB / 81920MiB | 100% Default |
| | | Disabled |
+-------------------------------+----------------------+----------------------+
| 2 NVIDIA A800-SXM... On | 00000000:52:00.0 Off | 0 |
| N/A 68C P0 398W / 400W | 75756MiB / 81920MiB | 100% Default |
| | | Disabled |
+-------------------------------+----------------------+----------------------+
| 3 NVIDIA A800-SXM... On | 00000000:57:00.0 Off | 0 |
| N/A 58C P0 341W / 400W | 75994MiB / 81920MiB | 100% Default |
| | | Disabled |
+-------------------------------+----------------------+----------------------+
| 4 NVIDIA A800-SXM... On | 00000000:8D:00.0 Off | 0 |
| N/A 56C P0 319W / 400W | 70084MiB / 81920MiB | 100% Default |
| | | Disabled |
+-------------------------------+----------------------+----------------------+
| 5 NVIDIA A800-SXM... On | 00000000:92:00.0 Off | 0 |
| N/A 70C P0 354W / 400W | 76314MiB / 81920MiB | 100% Default |
| | | Disabled |
+-------------------------------+----------------------+----------------------+
| 6 NVIDIA A800-SXM... On | 00000000:BF:00.0 Off | 0 |
| N/A 73C P0 360W / 400W | 75876MiB / 81920MiB | 100% Default |
| | | Disabled |
+-------------------------------+----------------------+----------------------+
| 7 NVIDIA A800-SXM... On | 00000000:C5:00.0 Off | 0 |
| N/A 57C P0 364W / 400W | 80404MiB / 81920MiB | 100% Default |
| | | Disabled |
+-------------------------------+----------------------+----------------------+
嘎嘎快啊