OCL-PDE: A Generative Framework for PDE Inverse Problems with Observation-Complementary Latents
Authors: Ding Yang, Chuqi Chen, Chang Ma, Yang Xiang
Organizations: Department of Mathematics, The Hong Kong University of Science and Technology, Hong Kong · Department of Mathematics, University of Michigan, Ann Arbor, USA · Department of Materials, The Hong Kong University of Science and Technology, Hong Kong · Algorithms of Machine Learning and Autonomous Driving Research Lab, HKUST Shenzhen-Hong Kong Collaborative Innovation Research Institute, Shenzhen, China
Partial differential equation (PDE) inverse problems are often ill-posed, making fine-scale details difficult to recover. We address this problem by introducing a learned observation-complementary latent representation that preserves reconstruction-relevant information and is combined with the observation to reconstruct the unknown field. Building on this representation, we propose OCL-PDE, a generative framework that encourages the observation to guide large-scale structure and the latent to supply complementary fine-scale details. OCL-PDE is built on a physics-aware autoencoder (AE) and conditional Flow Matching, supporting inverse reconstruction as well as forward PDE prediction. Experiments demonstrate improved reconstruction accuracy and fine-detail recovery compared with the evaluated baselines.
Figures & tables
Figure 1: Overview of OCL-PDE. The framework learns observation-complementary latents and generates them conditioned on observations to recover unknown fields. (A) The physics-aware autoencoder predicts the PDE response uc and encodes observation-complementary information in a latent z ; the decoder combines uc and latent z to reconstruct the input field. (B) With the autoencoder frozen, the conditional Flow learns to transform Gaussian noise into the encoder’s latents z guided by the observed response. (C) At inference, the Flow generates a latent from noise conditioned on the available observation y , and the decoder combines the generated latent z and y to recover the unknown field c .
Figure 2: Allen–Cahn evolution of a trajectory from t=0 to t=4 .
Method
ϕ0 relative L2 mean ± std.
Terminal-field relative L2 at t=4 ; mean ± std.
Test time (s/field)
PINO ( Li et al., 2024 )
0.18496±0.04341
0.03110±0.01316
–
DGenNO ( Zang and Koutsourelakis, 2025 ) ( d=512 )
0.66444±0.33967
0.62601±0.20541
73.51
Conditional EDM+PDE ( Karras et al., 2022 )
0.41914±0.05692
0.41826±0.07390
12.42
DPS (L2 guidance) ( Chung et al., 2023 )
0.45889±0.14540
0.18284±0.10136
27.56
No- Z ablation
0.09827±0.01863
0.01679±0.01108
–
OCL-PDE
0.05897±0.01817
0.01386±0.00547
0.9150
Table 1: Allen–Cahn initial-field and terminal-field relative L2 errors on 20 held-out trajectories, with test time per field.
Figure 3: Allen–Cahn initial-field recovery. Rows show reconstructions, absolute initial-field errors, spectral-method evolutions to t=4 , and absolute terminal-field errors. We report initial-field and terminal-field errors in relative L2 .
Method
Noise ρ=1%
Noise ρ=3%
a r0
a r20
u r0
u r20
a r0
a r20
u r0
u r20
PINO
0.03836
0.03669
0.00452
0.00450
0.05252
0.03694
0.00580
0.00456
Conditional EDM+PDE
0.09808
0.09912
0.02349
0.02398
0.09927
0.09893
0.02372
0.02400
No- Z ablation
0.03605
0.03151
0.00345
0.00318
0.05127
0.04034
0.00531
0.00409
OCL-PDE
0.03456
0.02249
0.00310
0.00265
0.05239
0.02381
0.00520
0.00285
Table 2: GRF coefficient reconstruction on 16 test fields with 50% clean-anchor coverage: mean relative L2 errors of the recovered coefficient ( a ) and corresponding pressure ( u ), before (r0) and after (r20) pressure correction. Pressure is computed from each recovered coefficient using conservative finite differences.
Figure 4: Continuous coefficient recovery before and after pressure correction at 3% noise and 50% clean-anchor coverage. We show the pressure observation, reference coefficient, reconstructions, and absolute coefficient errors, and report coefficient reconstruction errors in relative L2 .
Method
2% (318 points)
5% (794 points)
10% (1588 points)
Hard error ↓
u rel. L2↓
Time
Hard error ↓
u rel. L2↓
Time
Hard error ↓
u rel. L2↓
Time
PINO
0.06800
0.08264
-
0.05070
0.06317
-
0.04572
0.05456
-
DGenNO ( d=1024 )
0.13957
0.10923
99.02
0.14084
0.11891
96.24
0.14459
0.12381
84.42
DiffusionPDE ( Huang et al., 2024 )
0.15472
0.06302
164.8
0.12350
0.05192
164.5
0.10744
0.04561
164.6
No- Z
0.04659
0.02709
-
0.03454
0.01950
-
0.03143
0.01753
-
OCL-PDE
0.03524
0.01919
0.3417
0.02357
0.01199
0.3437
0.02105
0.01086
0.3440
Table 3: Binary coeficient reconstruction on 64 test fields: hard pixel error of the recovered coefficient, relative L2 error of the corresponding pressure, and inference time (seconds per field). Pressure is computed from each recovered hard coefficient using conservative finite differences.
Figure 5: Binary coefficient recovery on the same held-out field at 2% , 5% , and 10% observation rates (top to bottom). Percentages below reconstructions are hard pixel errors.
Figure 6: Allen–Cahn reconstructions for one pair of samples, swapping y or z between rows or setting either input to zero. Errors are relative L2 against each row’s ground truth.
Figure 7: GRF Darcy latent correction in loga (Sample 0). The last three columns show what the base ( z=0 ) misses, what the latent adds, and what remains unrecovered, respectively. Coefficient errors are relative L2 .
Appendix figures & tables18 assets
Supplementary material from the paper’s appendix.
Appendix
Task
Spatial condition supplied to C
Latent/velocity shape
Scalar inputs
Allen–Cahn
ηAC=[ϕ4,1] on 1282
8×8×8
τ and tcond=4
GRF Darcy, no anchors
ηlow=[u/su,M] on 322
4×16×16
τ only
GRF Darcy, clean anchors
ηMF=[u/su,M,MH] on 322
4×16×16
τ only
Binary Darcy
ηbin=[yq/su,Mq] on 1282
4×16×16
τ only
Appendix
Table 4: Spatial inputs to the Flow condition extractor C . Here ϕ is the Allen–Cahn solution and ϕ4=ϕ(x,4) is its observed terminal field ( y ); 1 is the all-one validity mask. For GRF Darcy, u denotes the native 322 pressure observation; for Binary Darcy, yq is the raw zero-filled 1282 pressure tensor. The quantity su is the training-set pressure standard deviation. In the clean-anchor row, selected noisy values in u have been replaced with clean anchors. The masks M and Mq mark observed pressure nodes, and MH marks clean anchors. In GRF Darcy, Flow receives native-grid observations. Flow time τ and physical time tcond are separate scalar inputs; the noise level ρ is not supplied to any Flow.
Task
Field grid
Latent C×H×W
AE
Log-var
Flow
Total
Allen–Cahn
128×128
8×8×8
30,650,596
72
22,080,456
52,731,124
GRF Darcy
128×128
4×16×16
30,313,272
20
10,417,444
40,730,716
Binary Darcy
128×128
4×16×16
30,313,272
20
10,503,668
40,816,960
Appendix
Table 5: Audited parameter counts for the models used in formal inference. The GRF Flow with clean anchors has one additional clean-anchor-mask condition channel.
Method
d
Initial ϕ0
Learned response
Solver response
Time (s)
DGenNO
512
1.57088±0.51192
0.36875±0.20238
0.67583±0.33643
16.67510±3.37500
Appendix
Table 6: Paper-aligned Allen–Cahn task adaptation ( N=20 ). Errors are relative L2 . The discrepancy between learned and independently solved terminal responses indicates a forward-surrogate limitation.
Method
d
ρ
Coefficient a
Solver- u
Time (s)
DGenNO
1024
0
0.71855±0.26673
0.19793±0.08747
24.01364±3.89045
DGenNO
1024
0.01
0.66729±0.25667
0.20109±0.10271
24.22199±5.68484
DGenNO
1024
0.03
0.71316±0.24072
0.20244±0.08668
25.00300±4.82461
Appendix
Table 7: Continuous Darcy results using the original DGenNO optimization procedure on the coarse pressure grid ( N=64 per setting). Errors are relative L2 .
Method
0% (0)
5% (45)
10% (90)
15% (135)
20% (180)
PINO
0.04029→0.04558
0.04012→0.04403
0.04009→0.04267
0.03989→0.04064
0.03960→0.03944
Conditional EDM+PDE
0.10212→0.11001
0.10014→0.10678
0.09885→0.10398
0.09716→0.10090
0.09528→0.09776
No- Z ablation
0.04013→0.04370
0.03992→0.04182
0.03968→0.04034
0.03902→0.03698
0.03863→0.03530
OCL-PDE
0.03967→0.04297
0.03934→0.04217
0.03910→0.03884
0.03850→0.03412
0.03798→0.03027
Appendix
Table 8: GRF coefficient relative L2 at ρ=1% with 0–20% clean-anchor coverage. Each cell reports round 0 → round 20; parentheses give the number of clean anchors. Lower is better.
Method
25% (225)
30% (270)
35% (315)
40% (360)
45% (405)
50% (450)
PINO
0.03946→0.03874
0.03936→0.03784
0.03914→0.03729
0.03892→0.03705
0.03875→0.03686
0.03836→0.03669
Conditional EDM+PDE
0.09441→0.09654
0.09468→0.09653
0.09486→0.09633
0.09525→0.09651
0.09647→0.09754
0.09808→0.09912
No- Z ablation
0.03823→0.03436
0.03790→0.03303
0.03738→0.03221
0.03692→0.03192
0.03670→0.03168
0.03605→0.03151
OCL-PDE
0.03756→0.02833
0.03727→0.02549
0.03663→0.02360
0.03581→0.02324
0.03527→0.02271
0.03456→0.02249
Appendix
Table 9: GRF coefficient relative L2 at ρ=1% with 25–50% clean-anchor coverage. Each cell reports round 0 → round 20; parentheses give the number of clean anchors. Lower is better.
Method
0% (0)
5% (45)
10% (90)
15% (135)
20% (180)
PINO
0.06365→0.06083
0.06292→0.05531
0.06223→0.05116
0.06117→0.04530
0.05990→0.04240
Conditional EDM+PDE
0.10497→0.12520
0.10276→0.11878
0.10129→0.11278
0.09977→0.10632
0.09779→0.10037
No- Z ablation
0.05806→0.06051
0.05780→0.05700
0.05741→0.05361
0.05668→0.04975
0.05594→0.04705
OCL-PDE
0.06092→0.06599
0.06041→0.06072
0.05994→0.05442
0.05927→0.04451
0.05827→0.03895
Appendix
Table 10: GRF coefficient relative L2 at ρ=3% with 0–20% clean-anchor coverage. Each cell reports round 0 → round 20; parentheses give the number of clean anchors. Lower is better.
Method
25% (225)
30% (270)
35% (315)
40% (360)
45% (405)
50% (450)
PINO
0.05858→0.04053
0.05782→0.03887
0.05667→0.03791
0.05548→0.03750
0.05395→0.03727
0.05252→0.03694
Conditional EDM+PDE
0.09668→0.09789
0.09680→0.09735
0.09676→0.09642
0.09698→0.09636
0.09812→0.09739
0.09927→0.09893
No- Z ablation
0.05516→0.04560
0.05487→0.04344
0.05411→0.04221
0.05316→0.04156
0.05204→0.04085
0.05127→0.04034
OCL-PDE
0.05731→0.03597
0.05691→0.03019
0.05625→0.02633
0.05488→0.02566
0.05317→0.02457
0.05239→0.02381
Appendix
Table 11: GRF coefficient relative L2 at ρ=3% with 25–50% clean-anchor coverage. Each cell reports round 0 → round 20; parentheses give the number of clean anchors. Lower is better.
Method
a relative L2
Solver- u relative L2
Mean time (s/field)
ρ=0
ρ=0.01
ρ=0.03
ρ=0
ρ=0.01
ρ=0.03
PINO
0.03561
0.03986
0.06239
0.00430
0.00471
0.00711
0.00141
DGenNO ( d=1024 )
0.15056
0.14958
0.15234
0.03358
0.03316
0.03405
99.74
Conditional EDM+PDE
0.09575
0.09636
0.09943
0.02633
0.02637
0.02674
12.25
No- Z ablation
0.02742
0.03858
0.05704
0.00318
0.00371
0.00629
0.01571
OCL-PDE
0.01807
0.03686
0.05740
0.00192
0.00334
0.00620
2.541
Appendix
Table 12: Robustness of continuous Darcy recovery to additive pressure noise on the aligned 32×32 pressure grid. Independent Gaussian noise with standard deviation ρsu is added to all interior pressure values; the boundary remains zero. The case ρ=0 is noise-free. Reported coefficient and solver- u errors are means over 64 held-out fields. For each method with recorded timing, test time is the mean per-field inference time over all three noise levels, excluding numerical Darcy solves; “–” denotes unavailable timing. Solver- u denotes an independent numerical Darcy solve from each reconstructed coefficient. Lower is better.
Method
2% (318 points)
5% (794 points)
10% (1588 points)
Boundary F1 ↑
ASSD (px) ↓
HD95 (px) ↓
Boundary F1 ↑
ASSD (px) ↓
HD95 (px) ↓
Boundary F1 ↑
ASSD (px) ↓
HD95 (px) ↓
PINO
0.47774
3.43339
13.20167
0.60188
2.40210
9.76224
0.65318
2.12762
9.99703
DGenNO ( d=1024 )
0.49796
5.12891
21.74188
0.50092
5.21081
22.72245
0.49330
5.39692
22.19505
DiffusionPDE
0.3540
7.6068
29.0139
0.4270
6.5002
26.5313
0.4493
6.1458
25.1457
No- Z
0.6279
2.8237
13.3906
0.7514
2.0703
10.8046
0.7894
1.8443
9.4692
OCL-PDE
0.7509
1.9840
10.0763
0.8721
1.2133
6.4314
0.8943
0.9803
5.2465
Appendix
Table 13: Additional Binary Darcy metrics at 2% , 5% , and 10% observation rates. Boundary F1 uses a one-pixel tolerance; ASSD and HD95 are measured in pixels. Bold values are best within each observation rate.
Method
d
Observed
Hard error
Solver- u
Time (s)
DGenNO
1024
2%
0.16463±0.07715
0.13248±0.06821
25.21020±5.67132
DGenNO
1024
5%
0.18134±0.10124
0.14612±0.08035
26.16990±2.63666
DGenNO
1024
10%
0.17399±0.07537
0.15497±0.09822
24.58750±5.65273
Appendix
Table 14: DGenNO with the original inference procedure for Binary Darcy from random pressure observations ( N=64 per setting). Entries are mean ± sample standard deviation. Both errors are reported as ratios.
Observation density
Method
Clean
80 dB
50 dB
2%
PINO
0.068003
0.067999
0.068479
No- Z
0.046590
0.046590
0.047270
OCL-PDE
0.035237
0.035226
0.036256
5%
PINO
0.050697
0.050689
0.050801
No- Z
0.034540
0.034532
0.035040
OCL-PDE
0.023565
0.023566
0.024655
Appendix
Table 15: Binary Darcy reconstruction under observation noise without retraining or refinement. Mean hard pixel errors over 64 fields are reported as fractions.
Figure 8: DiffusionPDE coefficient-observation sanity check with the main experiment’s epoch 350 EMA checkpoint. Rows show the same held-out field at 2% , 5% , and 10% random pressure observation rates. Columns show observed pressure, the 500 fixed coefficient observations, ground truth, pressure-only recovery, and recovery with both types of observations. Reconstructed coefficients are thresholded at the phase midpoint; annotations report hard pixel error and solver- u relative L2 error from an independent numerical solve.
Figure 9: Full Allen–Cahn decoder-branch intervention for two fixed test pairs: trajectories 6 and 15 in the first two rows, and trajectories 0 and 3 in the last two rows. Columns show the reference field, matched reconstruction, exchanged observation, exchanged latent, zero latent, and zero observation. The plot labels U and Z denote observation y and latent z , respectively. Each reconstruction is annotated with its relative L2 error.
Reconstruction
Hard error
Ephysical
Ef
Ehi
Q
Allen–Cahn: n=20 , f=ϕ(⋅,0)
DθD(z=0,y)
–
100.67±0.62
100.67±0.62
188.76±23.43
0
DθD(z⋆,y)
–
2.66±0.72
2.66±0.72
55.62±3.47
0.9993
DθD(zflow,y)
–
5.90±1.82
5.90±1.82
78.95±3.99
0.9964
GRF Darcy: n=64 , f=loga
DθD(z=0,y)
–
3.66±0.93
9.08±2.51
97.98±2.42
0
Appendix
Table 16: Fixed-observation latent diagnostics. Errors are percentages (mean ± sample standard deviation); Q is the pooled analysis-field squared-error reduction relative to z=0 . The oracle uses the ground-truth encoder mean μ . Flow uses K=64 samples for Allen–Cahn and GRF Darcy, and K=16 for Binary Darcy. Binary outputs are thresholded after averaging phase probabilities; hard pixel error applies only to Binary Darcy.
Figure 10: GRF Darcy latent corrections. Flow-generated reconstruction and zero-latent base, with the target residual, latent correction, and remaining error in f=loga . We report coefficient reconstruction errors in relative L2 .
Figure 11: Allen–Cahn latent corrections. Flow-generated reconstruction and zero-latent base, with the target residual, latent correction, and remaining error in f=ϕ(⋅,0) . We report initial-field reconstruction errors in relative L2 .
Figure 12: Binary Darcy latent corrections at 5% observations. Flow-generated reconstruction and zero-latent base, with the target residual, latent correction, and remaining error in f=loga . We report hard pixel errors.
Reconstructing PDE solutions from sparse observations is a core challenge in scientific computing. We present FM4PDE, a flow-matching generative framework that learns the joint distribution of PDE coefficients (or initial states) and solutions (or final states), enabling both forward simulation and inverse recovery with limited paired data. At inference, sampling is guided by a composite loss that enforces agreement with sparse measurements and reduces the PDE residual; we support deterministic, stochastic, and hybrid samplers. We provide error guarantees for these guided procedures. For the deterministic optimizer, a coercivity condition ensures trajectory boundedness and a phase-wise contraction yields logarithmic complexity in the target accuracy. For the stochastic sampler, we introduce adaptive guidance and assume dissipativity of the velocity field to obtain uniform moment bounds independent of the noise-floor parameter. This leads to polynomial-time error bounds, and a matching lower bound shows constant guidance induces an unavoidable positive bias, motivating adaptivity. A hybrid deterministic-stochastic analysis is also provided. Experiments on static and time-dependent benchmark PDEs demonstrate competitive accuracy and faster inference than diffusion-based generative models.
Xifeng Zhang, Jin Zhao
School of Mathematical Science Capital Normal University Beijing, 100048, China · Academy for Multidisciplinary Studies Capital Normal University2026 Beijing, 100048, China
Recovering complete physical fields from sparse observations is challenging because the measurements may not uniquely determine the underlying state. Diffusion-based PDE solvers address this problem through iterative sampling whereas neural operators provide deterministic one-pass predictions. We propose SCOPE (Sparse-Context Observability-aware Predictive Embeddings) to recover complete PDE fields from sparse observations by coupling full-field latent prediction with physical reconstruction. A shared decoder reconstructs fields from both predicted and complete-view representations so that representation learning is guided by both physical recovery and latent matching. We derive a quadratic risk decomposition at fixed teacher-decoder pairs showing why optimal latent prediction need not yield optimal field reconstruction. We also establish sufficient conditions for decoder improvements on complete inputs to transfer to recovery from partial observations. Experiments across five PDE settings show that SCOPE outperforms mask-aware neural operators on all ten forward and inverse tasks and achieves lower errors than those reported for diffusion-based solvers including DiffusionPDE and FunDPS. Decoder-only adaptation further improves recovery without retraining the backbone while retaining deterministic single-pass inference.
Ruichen Xu, Siyao Wang, Fang Wan +8
Stony Brook University · University of California, Davis · Independent Research +3
Scientific measurements are often bottlenecked by suboptimal conditions, whether that be noise, incomplete spatial coverage, or limited resolution, rendering accurate field reconstruction a difficult task. We introduce LatentPDE, a latent diffusion framework designed to simultaneously resolve sparse-observation reconstruction and super-resolution. While existing physics-guided diffusion models typically rely on soft loss penalties or uninterpretable representations, our approach enforces physical compliance by constructing an inherently interpretable latent space. Specifically, we parameterize the latent variables directly as the coefficients and source terms of an assumed governing PDE. In doing so, LatentPDE is able to reliably reconstruct dynamics across highly disparate and structured data gaps. Empirical results on diverse configurations demonstrate that our model achieves high-fidelity recovery at any desired resolution while also tracking the underlying predictive uncertainty.
Valerie Tsao, Nathaniel Chaney, Manolis Veveakis
Department of Civil & Environmental Engineering, Duke University, NC, USA.