readme: ---
  pipeline_tag: sentence-similarity
  tags:
  - sentence-transformers
  - feature-extraction
  - sentence-similarity
  - transformers
  - semantic-search
  - chinese
  ---
  
  # DMetaSoul/sbert-chinese-qmc-finance-v1-distill
  
  此模型是之前[开源金融问题匹配模型](https://huggingface.co/DMetaSoul/sbert-chinese-qmc-finance-v1)的蒸馏轻量化版本（仅4层 BERT），适用于**金融领域的问题匹配**场景，比如：
  
  - 8千日利息400元? VS 10000元日利息多少钱
  - 提前还款是按全额计息 VS 还款扣款不成功怎么还款？
  - 为什么我借钱交易失败 VS 刚申请的借款为什么会失败
  
  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 5% 左右（具体结果详见下文评估小节）。
  
  # Usage
  
  ## 1. Sentence-Transformers
  
  通过  [sentence-transformers](https://www.SBERT.net) 框架来使用该模型，首先进行安装：
  
  ```
  pip install -U sentence-transformers
  ```
  
  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：
  
  ```python
  from sentence_transformers import SentenceTransformer
  sentences = ["到期不能按时还款怎么办", "剩余欠款还有多少？"]
  
  model = SentenceTransformer('DMetaSoul/sbert-chinese-qmc-finance-v1-distill')
  embeddings = model.encode(sentences)
  print(embeddings)
  ```
  
  ## 2. HuggingFace Transformers
  
  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：
  
  ```python
  from transformers import AutoTokenizer, AutoModel
  import torch
  
  
  #Mean Pooling - Take attention mask into account for correct averaging
  def mean_pooling(model_output, attention_mask):
      token_embeddings = model_output[0] #First element of model_output contains all token embeddings
      input_mask_expanded = attention_mask.unsqueeze(-1).expand(token_embeddings.size()).float()
      return torch.sum(token_embeddings * input_mask_expanded, 1) / torch.clamp(input_mask_expanded.sum(1), min=1e-9)
  
  
  # Sentences we want sentence embeddings for
  sentences = ["到期不能按时还款怎么办", "剩余欠款还有多少？"]
  
  # Load model from HuggingFace Hub
  tokenizer = AutoTokenizer.from_pretrained('DMetaSoul/sbert-chinese-qmc-finance-v1-distill')
  model = AutoModel.from_pretrained('DMetaSoul/sbert-chinese-qmc-finance-v1-distill')
  
  # Tokenize sentences
  encoded_input = tokenizer(sentences, padding=True, truncation=True, return_tensors='pt')
  
  # Compute token embeddings
  with torch.no_grad():
      model_output = model(**encoded_input)
  
  # Perform pooling. In this case, mean pooling.
  sentence_embeddings = mean_pooling(model_output, encoded_input['attention_mask'])
  
  print("Sentence embeddings:")
  print(sentence_embeddings)
  ```
  
  ## Evaluation
  
  这里主要跟蒸馏前对应的 teacher 模型作了对比：
  
  *性能：*
  
  |            | Teacher               | Student             | Gap   |
  | ---------- | --------------------- | ------------------- | ----- |
  | Model      | BERT-12-layers (102M) | BERT-4-layers (45M) | 0.44x |
  | Cost       | 23s                   | 12s                 | -47%  |
  | Latency    | 38ms                  | 20ms                | -47%  |
  | Throughput | 418 sentence/s        | 791 sentence/s      | 1.9x  |
  
  *精度：*
  
  |                | **csts_dev** | **csts_test** | **afqmc** | **lcqmc** | **bqcorpus** | **pawsx** | **xiaobu** | **Avg** |
  | -------------- | ------------ | ------------- | --------- | --------- | ------------ | --------- | ---------- | ------- |
  | **Teacher**    | 77.40%       | 74.55%        | 36.00%    | 75.75%    | 73.24%       | 11.58%    | 54.75%     | 57.61%  |
  | **Student**    | 75.02%       | 71.99%        | 32.40%    | 67.06%    | 66.35%       | 7.57%     | 49.26%     | 52.80%  |
  | **Gap** (abs.) | -            | -             | -         | -         | -            | -         | -          | -4.81%  |
  
  *基于1万条数据测试，GPU设备是V100，batch_size=16，max_seq_len=256*
  
  ## Citing & Authors
  
  E-mail: xiaowenbin@dmetasoul.com