Generalized Context in Cross Attention for Transfer Learning of Disjoint Tabular Data
Authors: Kazi F. Akhter, Ibna Kowsar, Manar D. Samad
Organizations: Department of Computer Science Tennessee State University Nashville, TN, USA · Department of Computer Science North Carolina Agricultural and Technical State University Greensboro, NC, USA
Unlike images and text, applying transfer learning to tabular data is challenging due to heterogeneity in feature types, structures, and semantics across disparate domains. Existing methods assume shared features across data tables to enable knowledge transfer between domains, which is unrealistic in practice. \mds{This paper introduces generalized context learning to remove the requirement of shared features across domains. The generalized context captured by transformer projection weights for key, value, and query provides rule-based generalization rather than the domain-specific context conventionally learned from transformer activations. Projection weights for key from the source domain interact with the weight for query in the target domain to achieve Cross-domain Attention Transfer Learning (CATTLE) in a data-agnostic manner. Our experiments on ten pairs of disjoint source-target data sets show that CATTLE can learn generalized context from a single source data set and is rank-wise and statistically superior to nine state-of-the-art baselines, including machine learning, deep learning, and transfer learning methods using large-scale pre-trained models. CATTLE achieves the best average rank (2.9) and delivers a 3.7% average AUROC gain over the baseline methods.} The CATTLE source code is available at https://tinyurl.com/pr5s8ywn.
Figures & tables
Figure 1: Overview of the CATTLE framework. Attention-related weights from a pretrained Gated Feature Tokenizer Transformer (gFTT) trained on source data are transferred into a newly initialized gFTT, which is then finetuned using target data. Emb. = Embedding, Cat. = Categorical, and Num. = Numerical features.
Type
OpenML ID
Data set
Domain
Samples
Features
Numeric
Categorical
Classes
Source Data sets
14
mfeat-fourier (MF)
Shape Measurements
2000
76
76
0
10
31
credit-g (CG)
Banking
1000
20
7
13
2
38
sick (SK)
Thyroid Disease
3772
29
7
22
2
980
optdigits (DG)
Optical Digits
5620
64
64
0
2
1504
steel-plates-fault (SP)
Manufacturing
1941
33
33
0
2
40664
car-evaluation (CE)
Car Pricing
1728
21
0
21
4
Table 1: Summary of source and target data sets for transfer learning.
Figure 2: Transfer learning loss curves: (a) self‐supervised pretraining, (b) supervised pretraining, (c) finetuning a self-supervised pretrained model using a target data set, and (d) finetuning a supervised pretrained model using a target data set.
Parameter
Distribution
XGBoost [ 13 ]
max_depth
UniformInt[1, 10]
learning_rate
LogUniform[ exp(−7) , 1]
n_estimators
UniformInt[100, 4000]
subsample
UniformFloat[0.2, 1.0]
colsample_bytree
UniformFloat[0.2, 1.0]
Table 2: Hyperparameter search space for all baselines and proposed methods.
Logistic Regression
XGBoost
MLP
ResNet
FT- Transformer
TabNet
XTab
CM2
TransTab
CATTLE Supervised
CATTLE Self-Supervised
Target
Source
Source
Source
DB
0.822 (0.04)
0.810 (0.04)
0.798 (0.03)
0.818 (0.03)
0.788 (0.04)
0.643 (0.03)
52 AutoML Data sets
0.834 (0.02)
Open Tabs 2000 Data sets
0.803 (0.03)
CD
0.799 (0.04)
0.803 (0.04)
0.807 (0.04)
CG
0.818 (0.04)
0.808 (0.04)
0.819 (0.04)
VH
0.935 (0.01)
0.925 (0.01)
0.917 (0.01)
0.855 (0.01)
0.914 (0.01)
0.794 (0.10)
0.935 (0.01)
0.893 (0.01)
MF
0.928 (0.01)
0.940 (0.01)
0.933 (0.01)
DG
0.935 (0.01)
0.932 (0.01)
0.942 (0.01)
CM
0.703 (0.02)
0.727 (0.02)
0.704 (0.02)
0.695 (0.03)
0.724 (0.03)
0.681 (0.08)
0.721 (0.02)
0.729 (0.02)
CH
0.726 (0.01)
0.721 (0.03)
0.729 (0.02)
Table 3: Average area under the ROC curve (AUROC) and corresponding performance rank. Two-letter acronyms of the source and target data sets are taken from Table 1 . Traditional deep and machine learning methods for tabular data are trained and tested directly on target data sets without pretraining on the source.
Logistic Regression
XGBoost
MLP
ResNet
FT- Transformer
TabNet
XTab
CM2
TransTab
CATTLE Supervised
CATTLE Self-Supervised
Target
Source
Source
Source
DB
0.747 (0.04)
0.729 (0.04)
0.753 (0.03)
0.772 (0.03)
0.754 (0.04)
0.625 (0.05)
52 AutoML Data sets
0.764 (0.02)
Open Tabs 2000 Data sets
0.734 (0.02)
CD
0.734 (0.04)
0.735 (0.02)
0.740 (0.04)
CG
0.735 (0.04)
0.738 (0.05)
0.746 (0.05)
VH
0.736 (0.03)
0.753 (0.03)
0.754 (0.03)
0.721 (0.04)
0.767 (0.06)
0.574 (0.01)
0.753 (0.02)
0.664 (0.02)
MF
0.776 (0.03)
0.774 (0.02)
0.786 (0.02)
DG
0.766 (0.03)
0.758 (0.02)
0.773 (0.02)
CM
0.512 (0.04)
0.551 (0.03)
0.526 (0.02)
0.536 (0.04)
0.583 (0.06)
0.766 (0.01)
0.653 (0.03)
0.552 (0.03)
CH
0.510 (0.02)
0.534 (0.04)
0.640 (0.03)
Table 4: Comparison of CATTLE with other baseline methods based on average classification accuracy. Two-letter acronyms of the source and target data sets are taken from Table 1 . Traditional deep and machine learning methods for tabular data are trained and tested directly on target data sets without pretraining on the source.
Figure 3: Win matrix based on Wilcoxon signed-rank statistical tests. The cell value X/Y presents X as the number of times the row method statistically outperforms the column method. Y is the number of source–target data set pairs with statistically significant differences between a pair of methods.
Bottom Layers → Bottom Layers
Top Layers → Bottom Layers
gFTT s ( W0 ) → gFTT t ( W0 )
gFTT s ( W0,1 ) → gFTT t ( W0,1 )
gFTT s ( W0 ) → gFTT t ( W0,1 )
gFTT s ( WL ) → gFTT t ( W0 )
gFTT s ( WL,WL−1 ) → gFTT t ( W0,1 )
gFTT s ( WL ) → gFTT t ( W0,1 ) [Proposed]
Cardiovascular → diabetes
0.818 (0.06)
0.816 (0.06)
0.813 (0.06)
0.810 (0.05)
0.818 (0.05)
0.819 (0.05)
credit-g → diabetes
0.821 (0.06)
0.819 (0.06)
0.816 (0.06)
0.814 (0.06)
0.814 (0.05)
0.815 (0.06)
mfeat-fourier → vehicle
0.928 (0.01)
0.927 (0.01)
0.926 (0.01)
0.928 (0.02)
0.927 (0.01)
0.927 (0.01)
optdigits → vehicle
0.933 (0.01)
0.930 (0.01)
0.925 (0.01)
0.931 (0.02)
0.925 (0.01)
0.942 (0.01)
churn → cmc
0.745 (0.05)
0.751 (0.05)
0.747 (0.05)
0.746 (0.03)
0.747 (0.05)
0.749 (0.05)
Table 5: Effects of transferring attention layers from the source pretrained transformer (gFTT) to the downstream transformer. Attention layers are numbered from bottom (0) to top (L), as {0, 1, …, L-1, L} for the projection weight (W) matrices.
Figure 4: Effects of individual source data sets on the classification of the (downstream) cmc target data set. A source data set is used for self-supervised pretraining of the upstream model.
Source → Target
Anonymized
Word2Vec
Pre-trained BERT
Cardiovascular-Disease-dataset → diabetes
0.714 (0.06)
0.707 (0.05)
0.799 (0.04)
credit-g → diabetes
0.685 (0.04)
0.694 (0.05)
0.818 (0.04)
mfeat-fourier → vehicle
0.435 (0.06)
0.441 (0.03)
0.928 (0.01)
optdigits → vehicle
0.418 (0.05)
0.432 (0.03)
0.935 (0.01)
churn → cmc
0.582 (0.05)
0.610 (0.04)
0.726 (0.01)
sick → cmc
0.569 (0.06)
0.601 (0.04)
0.733 (0.02)
Table 6: Ablation study on categorical feature encoding strategies. The anonymized variant removes semantic information from feature names before learning their embeddings from scratch. The Word2Vec-style variant uses trainable token embeddings for feature names and categorical values. Embeddings for categorical feature names and values are extracted from pre-trained BERT [ 37 ] .
Source → Target
Random
Trained
Direct
Proposed
weights
weights
finetune
CATTLE
Cardiovascular-Disease-dataset → diabetes
0.812 (0.06)
0.810 (0.06)
0.799 (0.04)
0.819 (0.05)
credit-g → diabetes
0.811 (0.06)
0.815 (0.06)
0.818 (0.04)
0.815 (0.06)
mfeat-fourier → vehicle
0.901 (0.01)
0.912 (0.01)
0.928 (0.01)
0.927 (0.01)
optdigits → vehicle
0.932 (0.01)
0.927 (0.01)
0.935 (0.01)
0.942 (0.01)
churn → cmc
0.745 (0.04)
0.747 (0.05)
0.726 (0.01)
0.749 (0.05)
Table 7: Ablation study on cross-attention weight transfer mechanisms. The random - weights variant uses randomly selected weights from the pretrained model to remain frozen in the downstream. The trained - weights variant updates the proposed frozen pre-trained key - value projection weights in the downstream. The directfinetune variant directly finetunes the upstream pre-trained model on the target data without proposed weight transfer. Proposed CATTLE transfers selective pretrained key-value projection weights and keeps them frozen while finetuning the downstream model using target data.
Appendix figures & tables2 assets
Supplementary material from the paper’s appendix.
Appendix
Data set pairs
Top 4 Layers
Top 3 Layers
Top 2 Layers
Top 1 Layer
CD → DB
0.818(0.051)
0.814(0.055)
0.810(0.060)
0.821(0.057)
CE → PC1
0.787(0.071)
0.810(0.051)
0.833(0.047)
0.831(0.035)
CH → CM
0.735(0.046)
0.732(0.039)
0.741(0.043)
0.743(0.039)
CG → DB
0.803(0.063)
0.808(0.059)
0.806(0.063)
0.804(0.061)
MF → VH
0.932(0.014)
0.938(0.014)
0.929(0.015)
0.927(0.012)
DG → VH
0.928(0.010)
0.929(0.010)
0.926(0.010)
0.923(0.012)
Appendix
Table 8: Effects of the number of active attention layers of the pretrained gFTT model (supervised) on downstream target data classification (AUROC scores).
Target
TARTE
TabPFNv2
Source
CATTLE Supervised
CATTLE Self-Supervised
DB
0.815 (0.04)
0.816 (0.03)
CD
0.803 (0.05)
0.807 (0.05)
CG
0.808 (0.04)
0.819 (0.04)
VH
0.941 (0.01)
0.966 (0.01)
MF
0.940 (0.01)
0.936 (0.00)
DG
0.932 (0.01)
0.942 (0.01)
CM
0.737 (0.02)
0.756 (0.02)
CH
0.721 (0.03)
0.729 (0.02)
SK
0.726 (0.03)
0.738 (0.02)
Appendix
Table 9: Comparison of CATTLE (supervised and self-supervised) with TARTE and TabPFNv2 across multiple source–target tasks.