Intra-Document Cascading (IDCM)
We provide a retrieval trained IDCM model. Our model is trained on MSMARCO-Document with up to 2000 tokens.
This instance can be used to re-rank a candidate set of long documents. The base BERT architecure is a 6-layer DistilBERT.
If you want to know more about our intra document cascading model & training procedure using knowledge distillation check out our paper: https://arxiv.org/abs/2105.09816 🎉
For more information, training data, source code, and a minimal usage example please visit: https://github.com/sebastian-hofstaetter/intra-document-cascade
Configuration
- Trained with fp16 mixed precision
- We select the top 4 windows of size (50 + 2*7 overlap words) with our fast CK model and score them with BERT
- The published code here is only usable for inference (we removed the training code)
Model Code
from transformers import AutoTokenizer,AutoModel, PreTrainedModel,PretrainedConfig
from typing import Dict
import torch
from torch import nn as nn
class IDCM_InferenceOnly(PreTrainedModel):
'''
IDCM is a neural re-ranking model for long documents, it creates an intra-document cascade between a fast (CK) and a slow module (BERT_Cat)
This code is only usable for inference (we removed the training mechanism for simplicity)
'''
config_class = IDCM_Config
base_model_prefix = "bert_model"
def __init__(self,
cfg) -> None:
super().__init__(cfg)
#
# bert - scoring
#
if isinstance(cfg.bert_model, str):
self.bert_model = AutoModel.from_pretrained(cfg.bert_model)
else:
self.bert_model = cfg.bert_model
#
# final scoring (combination of bert scores)
#
self._classification_layer = torch.nn.Linear(self.bert_model.config.hidden_size, 1)
self.top_k_chunks = cfg.top_k_chunks
self.top_k_scoring = nn.Parameter(torch.full([1,self.top_k_chunks], 1, dtype=torch.float32, requires_grad=True))
#
# local self attention
#
self.padding_idx= cfg.padding_idx
self.chunk_size = cfg.chunk_size
self.overlap = cfg.overlap
self.extended_chunk_size = self.chunk_size + 2 * self.overlap
#
# sampling stuff
#
self.sample_n = cfg.sample_n
self.sample_context = cfg.sample_context
if self.sample_context == "ck":
i = 3
self.sample_cnn3 = nn.Sequential(
nn.ConstantPad1d((0,i - 1), 0),
nn.Conv1d(kernel_size=i, in_channels=self.bert_model.config.dim, out_channels=self.bert_model.config.dim),
nn.ReLU()
)
elif self.sample_context == "ck-small":
i = 3
self.sample_projector = nn.Linear(self.bert_model.config.dim,384)
self.sample_cnn3 = nn.Sequential(
nn.ConstantPad1d((0,i - 1), 0),
nn.Conv1d(kernel_size=i, in_channels=384, out_channels=128),
nn.ReLU()
)
self.sampling_binweights = nn.Linear(11, 1, bias=True)
torch.nn.init.uniform_(self.sampling_binweights.weight, -0.01, 0.01)
self.kernel_alpha_scaler = nn.Parameter(torch.full([1,1,11], 1, dtype=torch.float32, requires_grad=True))
self.register_buffer("mu",nn.Parameter(torch.tensor([1.0, 0.9, 0.7, 0.5, 0.3, 0.1, -0.1, -0.3, -0.5, -0.7, -0.9]), requires_grad=False).view(1, 1, 1, -1))
self.register_buffer("sigma", nn.Parameter(torch.tensor([0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1]), requires_grad=False).view(1, 1, 1, -1))
def forward(self,
query: Dict[str, torch.LongTensor],
document: Dict[str, torch.LongTensor],
use_fp16:bool = True,
output_secondary_output: bool = False):
#
# patch up documents - local self attention
#
document_ids = document["input_ids"][:,1:]
if document_ids.shape[1] > self.overlap:
needed_padding = self.extended_chunk_size - (((document_ids.shape[1]) % self.chunk_size) - self.overlap)
else:
needed_padding = self.extended_chunk_size - self.overlap - document_ids.shape[1]
orig_doc_len = document_ids.shape[1]
document_ids = nn.functional.pad(document_ids,(self.overlap, needed_padding),value=self.padding_idx)
chunked_ids = document_ids.unfold(1,self.extended_chunk_size,self.chunk_size)
batch_size = chunked_ids.shape[0]
chunk_pieces = chunked_ids.shape[1]
chunked_ids_unrolled=chunked_ids.reshape(-1,self.extended_chunk_size)
packed_indices = (chunked_ids_unrolled[:,self.overlap:-self.overlap] != self.padding_idx).any(-1)
orig_packed_indices = packed_indices.clone()
ids_packed = chunked_ids_unrolled[packed_indices]
mask_packed = (ids_packed != self.padding_idx)
total_chunks=chunked_ids_unrolled.shape[0]
packed_query_ids = query["input_ids"].unsqueeze(1).expand(-1,chunk_pieces,-1).reshape(-1,query["input_ids"].shape[1])[packed_indices]
packed_query_mask = query["attention_mask"].unsqueeze(1).expand(-1,chunk_pieces,-1).reshape(-1,query["attention_mask"].shape[1])[packed_indices]
#
# sampling
#
if self.sample_n > -1:
#
# ck learned matches
#
if self.sample_context == "ck-small":
query_ctx = torch.nn.functional.normalize(self.sample_cnn3(self.sample_projector(self.bert_model.embeddings(packed_query_ids).detach()).transpose(1,2)).transpose(1, 2),p=2,dim=-1)
document_ctx = torch.nn.functional.normalize(self.sample_cnn3(self.sample_projector(self.bert_model.embeddings(ids_packed).detach()).transpose(1,2)).transpose(1, 2),p=2,dim=-1)
elif self.sample_context == "ck":
query_ctx = torch.nn.functional.normalize(self.sample_cnn3((self.bert_model.embeddings(packed_query_ids).detach()).transpose(1,2)).transpose(1, 2),p=2,dim=-1)
document_ctx = torch.nn.functional.normalize(self.sample_cnn3((self.bert_model.embeddings(ids_packed).detach()).transpose(1,2)).transpose(1, 2),p=2,dim=-1)
else:
qe = self.tk_projector(self.bert_model.embeddings(packed_query_ids).detach())
de = self.tk_projector(self.bert_model.embeddings(ids_packed).detach())
query_ctx = self.tk_contextualizer(qe.transpose(1,0),src_key_padding_mask=~packed_query_mask.bool()).transpose(1,0)
document_ctx = self.tk_contextualizer(de.transpose(1,0),src_key_padding_mask=~mask_packed.bool()).transpose(1,0)
query_ctx = torch.nn.functional.normalize(query_ctx,p=2,dim=-1)
document_ctx= torch.nn.functional.normalize(document_ctx,p=2,dim=-1)
cosine_matrix = torch.bmm(query_ctx,document_ctx.transpose(-1, -2)).unsqueeze(-1)
kernel_activations = torch.exp(- torch.pow(cosine_matrix - self.mu, 2) / (2 * torch.pow(self.sigma, 2))) * mask_packed.unsqueeze(-1).unsqueeze(1)
kernel_res = torch.log(torch.clamp(torch.sum(kernel_activations, 2) * self.kernel_alpha_scaler, min=1e-4)) * packed_query_mask.unsqueeze(-1)
packed_patch_scores = self.sampling_binweights(torch.sum(kernel_res, 1))
sampling_scores_per_doc = torch.zeros((total_chunks,1), dtype=packed_patch_scores.dtype, layout=packed_patch_scores.layout, device=packed_patch_scores.device)
sampling_scores_per_doc[packed_indices] = packed_patch_scores
sampling_scores_per_doc = sampling_scores_per_doc.reshape(batch_size,-1,)
sampling_scores_per_doc_orig = sampling_scores_per_doc.clone()
sampling_scores_per_doc[sampling_scores_per_doc == 0] = -9000
sampling_sorted = sampling_scores_per_doc.sort(descending=True)
sampled_indices = sampling_sorted.indices + torch.arange(0,sampling_scores_per_doc.shape[0]*sampling_scores_per_doc.shape[1],sampling_scores_per_doc.shape[1],device=sampling_scores_per_doc.device).unsqueeze(-1)
sampled_indices = sampled_indices[:,:self.sample_n]
sampled_indices_mask = torch.zeros_like(packed_indices).scatter(0, sampled_indices.reshape(-1), 1)
# pack indices
packed_indices = sampled_indices_mask * packed_indices
packed_query_ids = query["input_ids"].unsqueeze(1).expand(-1,chunk_pieces,-1).reshape(-1,query["input_ids"].shape[1])[packed_indices]
packed_query_mask = query["attention_mask"].unsqueeze(1).expand(-1,chunk_pieces,-1).reshape(-1,query["attention_mask"].shape[1])[packed_indices]
ids_packed = chunked_ids_unrolled[packed_indices]
mask_packed = (ids_packed != self.padding_idx)
#
# expensive bert scores
#
bert_vecs = self.forward_representation(torch.cat([packed_query_ids,ids_packed],dim=1),torch.cat([packed_query_mask,mask_packed],dim=1))
packed_patch_scores = self._classification_layer(bert_vecs)
scores_per_doc = torch.zeros((total_chunks,1), dtype=packed_patch_scores.dtype, layout=packed_patch_scores.layout, device=packed_patch_scores.device)
scores_per_doc[packed_indices] = packed_patch_scores
scores_per_doc = scores_per_doc.reshape(batch_size,-1,)
scores_per_doc_orig = scores_per_doc.clone()
scores_per_doc_orig_sorter = scores_per_doc.clone()
if self.sample_n > -1:
scores_per_doc = scores_per_doc * sampled_indices_mask.view(batch_size,-1)
#
# aggregate bert scores
#
if scores_per_doc.shape[1] < self.top_k_chunks:
scores_per_doc = nn.functional.pad(scores_per_doc,(0, self.top_k_chunks - scores_per_doc.shape[1]))
scores_per_doc[scores_per_doc == 0] = -9000
scores_per_doc_orig_sorter[scores_per_doc_orig_sorter == 0] = -9000
score = torch.sort(scores_per_doc,descending=True,dim=-1).values
score[score <= -8900] = 0
score = (score[:,:self.top_k_chunks] * self.top_k_scoring).sum(dim=1)
if self.sample_n == -1:
if output_secondary_output:
return score,{
"packed_indices": orig_packed_indices.view(batch_size,-1),
"bert_scores":scores_per_doc_orig
}
else:
return score,scores_per_doc_orig
else:
if output_secondary_output:
return score,scores_per_doc_orig,{
"score": score,
"packed_indices": orig_packed_indices.view(batch_size,-1),
"sampling_scores":sampling_scores_per_doc_orig,
"bert_scores":scores_per_doc_orig
}
return score
def forward_representation(self, ids,mask,type_ids=None) -> Dict[str, torch.Tensor]:
if self.bert_model.base_model_prefix == 'distilbert': # diff input / output
pooled = self.bert_model(input_ids=ids,
attention_mask=mask)[0][:,0,:]
elif self.bert_model.base_model_prefix == 'longformer':
_, pooled = self.bert_model(input_ids=ids,
attention_mask=mask.long(),
global_attention_mask = ((1-ids)*mask).long())
elif self.bert_model.base_model_prefix == 'roberta': # no token type ids
_, pooled = self.bert_model(input_ids=ids,
attention_mask=mask)
else:
_, pooled = self.bert_model(input_ids=ids,
token_type_ids=type_ids,
attention_mask=mask)
return pooled
tokenizer = AutoTokenizer.from_pretrained("distilbert-base-uncased") # honestly not sure if that is the best way to go, but it works :)
model = IDCM_InferenceOnly.from_pretrained("sebastian-hofstaetter/idcm-distilbert-msmarco_doc")
Effectiveness on MSMARCO Passage & TREC Deep Learning '19
We trained our model on the MSMARCO-Document collection. We trained the selection module CK with knowledge distillation from the stronger BERT model.
For re-ranking we used the top-100 BM25 results. The throughput of IDCM should be ~600 documents with max 2000 tokens per second.
MSMARCO-Document-DEV
| MRR@10 | NDCG@10 | |
|---|---|---|
| BM25 | .252 | .311 |
| IDCM | .380 | .446 |
TREC-DL'19 (Document Task)
For MRR we use the recommended binarization point of the graded relevance of 2. This might skew the results when compared to other binarization point numbers.
| MRR@10 | NDCG@10 | |
|---|---|---|
| BM25 | .661 | .488 |
| IDCM | .916 | .688 |
For more metrics, baselines, info and analysis, please see the paper: https://arxiv.org/abs/2105.09816
Limitations & Bias
The model inherits social biases from both DistilBERT and MSMARCO.
The model is only trained on longer documents of MSMARCO, so it might struggle with especially short document text - for short text we recommend one of our MSMARCO-Passage trained models.
Citation
If you use our model checkpoint please cite our work as:
@inproceedings{Hofstaetter2021_idcm,
author = {Sebastian Hofst{\"a}tter and Bhaskar Mitra and Hamed Zamani and Nick Craswell and Allan Hanbury},
title = {{Intra-Document Cascading: Learning to Select Passages for Neural Document Ranking}},
booktitle = {Proc. of SIGIR},
year = {2021},
}
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