Neural Operator-Grounded Continuous Tensor Function Representation and Its Applications
Authors: Ruoyang Su, Xi-Le Zhao, Sheng Liu, Wei-Hao Wu, Yisi Luo, Michael K. Ng
Organizations: School of Mathematical Sciences, University of Electronic Science and Technology of China, Chengdu 611731, China · School of Mathematics and Statistics, Xi’an Jiaotong University, Xi’an 710049, China · Department of Mathematics, Hong Kong Baptist University, Hong Kong, China
Recently, continuous tensor functions have attracted increasing attention, because they can unifiedly represent data both on mesh grids and beyond mesh grids. However, since mode-n product is essentially discrete and linear, the potential of current continuous tensor function representations is still locked. To break this bottleneck, we suggest neural operator-grounded mode-n operators as a continuous and nonlinear alternative of discrete and linear mode-n product. Instead of mapping the discrete core tensor to the discrete target tensor, proposed mode-n operator directly maps the continuous core tensor function to the continuous target tensor function, which provides a genuine continuous representation of real-world data and can ameliorate discretization artifacts. Empowering with continuous and nonlinear mode-n operators, we propose a neural operator-grounded continuous tensor function representation (abbreviated as NO-CTR), which can more faithfully represent complex real-world data compared with classic discrete tensor representations and continuous tensor function representations. Theoretically, we also prove that any continuous tensor function can be approximated by NO-CTR. To examine the capability of NO-CTR, we suggest an NO-CTR-based multi-dimensional data completion model. Extensive experiments across various data on regular mesh grids (multi-spectral images and color videos), on mesh girds with different resolutions (Sentinel-2 images) and beyond mesh grids (point clouds) demonstrate the superiority of NO-CTR.
Figures & tables
Fig. 1: Discrete and linear mode- n operator and proposed continuous and nonlinear mode- n operator. The basic unit performed upon by discrete and linear mode- n operator is the mode- n fiber vectors of the discrete core tensor G , which are then mapped to the mode- n fiber vectors of the discrete target tensor X . The basic unit performed upon by continuous and nonlinear mode- n operator is the mode- n univariate fiber functions of the continuous core tensor function G , which are then mapped to the mode- n univariate fiber functions of the continuous target tensor function X .
Fig. 2: Visual and quantitative recovery results with discrete and linear mode- n operators (LRTFR [ 34 ] ), continuous and nonlinear mode- n operators (proposed NO-CTR) on the MSI Toy (top) and point cloud Frog (bottom) when the sampling rates are 10% .
Fig. 3: Flow chart of NO-CTR and the corresponding multi-dimensional data completion model. We first cleverly leverage neural operators to suggest continuous and nonlinear mode- n operators. Specifically, the basic unit performed upon by continuous and nonlinear mode- n operator is the mode- n univariate fiber functions of the continuous core tensor function G , which are then mapped to the mode- n univariate fiber functions of the continuous target tensor function X . Empowering with continuous and nonlinear mode- n operators, we propose a neural operator-grounded continuous tensor function representation (NO-CTR), which can faithfully represent continuous target tensor function X as a continuous core tensor function G and a series of continuous and nonlinear mode- n operators {F⟨n⟩}n=1N . To examine the capability of NO-CTR, we suggest an NO-CTR-based multi-dimensional data completion model.
TABLE I: Quantitative Recovery Results of MSI Completion
Fig. 4: Visual recovery results of MSI completion at a sampling rate of 10% .
TABLE II: Quantitative Recovery Results of Color Video Completion
Fig. 5: Visual recovery results of color video completion at a sampling rate of 10% .
TABLE III: Quantitative Recovery Results of Sentinel-2 Image Completion
Fig. 6: Visual recovery results of Sentinel-2 image completion at a sampling rate of 10% .
TABLE IV: Quantitative Recovery Results of Point Cloud Completion
Fig. 7: Visual recovery results of point cloud completion at a sampling rate of 10% .
Sampling Rate
10%
20%
MSI
Mode- n Operators
PSNR
SSIM
PSNR
SSIM
Flowers
No Operator
30.565
0.898
34.367
0.948
Discrete & Linear
39.175
0.984
43.119
0.984
Continuous & Nonlinear
42.591
0.994
49.717
0.999
Toy
No Operator
26.190
0.835
29.087
0.895
Discrete & Linear
38.907
0.982
41.395
0.991
TABLE V: Quantitative Recovery Results of MSI Completion With Different Mode- n Operators
Sampling Rate
10%
20%
MSI
Architecture
PSNR
SSIM
PSNR
SSIM
Flowers
No Operator
30.565
0.898
34.367
0.948
FNO
40.940
0.992
47.446
0.997
DeepONet
42.591
0.994
49.717
0.999
Toy
No Operator
26.190
0.835
29.087
0.895
FNO
41.167
0.994
46.076
0.998
TABLE VI: Quantitative Recovery Results of MSI Completion With Different Neural Operators
Sampling Rate
10%
20%
MSI
Core
PSNR
SSIM
PSNR
SSIM
Flowers
LRTFR
39.586
0.983
44.232
0.992
PE-MLP
42.086
0.993
47.326
0.998
SIREN
42.591
0.994
49.717
0.999
Toy
LRTFR
37.781
0.980
41.948
0.991
PE-MLP
40.831
0.993
45.765
0.998
TABLE VII: Quantitative Recovery Results of MSI Completion With Different Representation Methods for the Continuous Core Tensor Function
Sampling Rate
10%
20%
MSI
Method
PSNR
SSIM
Parameters
PSNR
SSIM
Parameters
Flowers
SIREN
38.681
0.977
16 711
46.041
0.995
47 671
LRTFR
36.879
0.965
130 191
43.249
0.991
331 023
NO-CTR
42.591
0.994
507 341
49.717
0.999
472 721
Toy
SIREN
37.259
0.974
16 711
45.306
0.995
47 671
LRTFR
37.661
0.975
130 191
43.099
0.991
595 231
TABLE VIII: Quantitative Recovery Results and Number of Parameters of MSI Completion With Different Continuous Tensor Function Representations
Fig. 8: Quantitative recovery results w.r.t. different numbers of sensors on the MSIs Flowers (left) and Toy (right) at a sampling rate of 10% .
Fig. 9: Quantitative recovery results w.r.t. different numbers of branch networks on the MSIs Flowers (left) and Toy (right) at a sampling rate of 10% .
Key Laboratory of Computing and Stochastic Mathematics (Ministry of Education), School of Mathematics and Statistics, Hunan Normal University · Department of Statistics and Data Science, Southern University of Science and Technology
Department of Biomedical Engineering, University of Basel, Allschwil, Switzerland · Harvard Medical School, Brigham and Women’s Hospital, Boston, United States
Department of Physics, CCTP and ITCP, University of Crete, 71303, Greece · Theoretical Physics Department, CERN, Geneva, Switzerland · Physik-Institut, Universität Zürich, 8057 Zürich, Switzerland