102 lines
4.2 KiB
Markdown
102 lines
4.2 KiB
Markdown
---
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pipeline_tag: sentence-similarity
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tags:
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- sentence-transformers
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- feature-extraction
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- sentence-similarity
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- transformers
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- semantic-search
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- chinese
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---
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# DMetaSoul/sbert-chinese-general-v2-distill
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此模型是之前[开源通用语义匹配模型](https://huggingface.co/DMetaSoul/sbert-chinese-general-v2)的蒸馏版本（仅4层 BERT），适用于**通用语义匹配**场景，从效果来看该模型在各种任务上**泛化能力更好且编码速度更快**。
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离线训练好的大模型如果直接用于线上推理，对计算资源有苛刻的需求，而且难以满足业务环境对延迟、吞吐量等性能指标的要求，这里我们使用蒸馏手段来把大模型轻量化。从 12 层 BERT 蒸馏为 4 层后，模型参数量缩小到 44%，大概 latency 减半、throughput 翻倍、精度下降 6% 左右（具体结果详见下文评估小节）。
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# Usage
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## 1. Sentence-Transformers
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通过 [sentence-transformers](https://www.SBERT.net) 框架来使用该模型，首先进行安装：
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```
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pip install -U sentence-transformers
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```
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然后使用下面的代码来载入该模型并进行文本表征向量的提取：
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```python
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from sentence_transformers import SentenceTransformer
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sentences = ["我的儿子！他猛然间喊道，我的儿子在哪儿？", "我的儿子呢！他突然喊道，我的儿子在哪里？"]
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model = SentenceTransformer('DMetaSoul/sbert-chinese-general-v2-distill')
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embeddings = model.encode(sentences)
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print(embeddings)
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```
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## 2. HuggingFace Transformers
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如果不想使用 [sentence-transformers](https://www.SBERT.net) 的话，也可以通过 HuggingFace Transformers 来载入该模型并进行文本向量抽取：
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```python
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from transformers import AutoTokenizer, AutoModel
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import torch
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#Mean Pooling - Take attention mask into account for correct averaging
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def mean_pooling(model_output, attention_mask):
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token_embeddings = model_output[0] #First element of model_output contains all token embeddings
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input_mask_expanded = attention_mask.unsqueeze(-1).expand(token_embeddings.size()).float()
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return torch.sum(token_embeddings * input_mask_expanded, 1) / torch.clamp(input_mask_expanded.sum(1), min=1e-9)
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# Sentences we want sentence embeddings for
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sentences = ["我的儿子！他猛然间喊道，我的儿子在哪儿？", "我的儿子呢！他突然喊道，我的儿子在哪里？"]
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# Load model from HuggingFace Hub
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tokenizer = AutoTokenizer.from_pretrained('DMetaSoul/sbert-chinese-general-v2-distill')
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model = AutoModel.from_pretrained('DMetaSoul/sbert-chinese-general-v2-distill')
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# Tokenize sentences
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encoded_input = tokenizer(sentences, padding=True, truncation=True, return_tensors='pt')
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# Compute token embeddings
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with torch.no_grad():
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model_output = model(**encoded_input)
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# Perform pooling. In this case, mean pooling.
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sentence_embeddings = mean_pooling(model_output, encoded_input['attention_mask'])
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print("Sentence embeddings:")
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print(sentence_embeddings)
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```
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## Evaluation
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这里主要跟蒸馏前对应的 teacher 模型作了对比：
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*性能：*
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| | Teacher | Student | Gap |
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| ---------- | --------------------- | ------------------- | ----- |
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| Model | BERT-12-layers (102M) | BERT-4-layers (45M) | 0.44x |
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| Cost | 23s | 12s | -47% |
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| Latency | 38ms | 20ms | -47% |
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| Throughput | 418 sentence/s | 791 sentence/s | 1.9x |
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*精度：*
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| | **csts_dev** | **csts_test** | **afqmc** | **lcqmc** | **bqcorpus** | **pawsx** | **xiaobu** | **Avg** |
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| -------------- | ------------ | ------------- | --------- | --------- | ------------ | --------- | ---------- | ------- |
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| **Teacher** | 77.19% | 72.59% | 36.79% | 76.91% | 49.62% | 16.24% | 63.15% | 56.07% |
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| **Student** | 76.49% | 73.33% | 26.46% | 64.26% | 46.02% | 11.83% | 52.45% | 50.12% |
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| **Gap** (abs.) | - | - | - | - | - | - | - | -5.95% |
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*基于1万条数据测试，GPU设备是V100，batch_size=16，max_seq_len=256*
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## Citing & Authors
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E-mail: xiaowenbin@dmetasoul.com |