Spatial Adapter

A post-hoc cascade adapter that extracts explicit low-rank spatial representations from the residuals of any frozen first-stage predictor, yielding closed-form covariance estimation and uncertainty quantification.

Installation

Requires Python 3.10+, Conda, and (optionally) CUDA 12.8+ for GPU.

git clone https://github.com/STLABTW/spatial-adapter.git
cd spatial-adapter

make conda-env                 # recommended: conda env + C++ extensions
# or
pip install -e ".[all]"        # pip-only

For Blackwell / sm_120 GPUs (e.g. RTX 5070 Ti):

pip install torch torchvision --index-url https://download.pytorch.org/whl/cu128 --force-reinstall

Quick Start

Option A — one-shot tuned fit (recommended)

Hides the (τ₁, τ₂) grid search behind a single call: runs a short Optuna sweep, refits at the best weights, returns the trained adapter plus the chosen τ's and the trials dataframe.

import torch
from spatial_adapter import SpatialAdapter, TrendModel

trend = TrendModel(num_continuous_features=5, hidden_layer_sizes=[], n_locations=100)

result = SpatialAdapter.fit_tuned(
    trend, train_loader,
    val_cont=val_X, val_y=val_Y, locs=station_coords,
    device=torch.device("cpu"),
    latent_dim=10,
    n_trials=10,              # per-seed Optuna budget (defaults to 10)
    seed=42,
    criterion="auto",         # see table below
)
result.adapter.reconstruct(val_X, val_Y)   # trained; ready to use
result.tau1, result.tau2                    # best weights chosen by Optuna
result.trials                               # pandas DataFrame of all trials

Validation criterion — what Optuna minimizes/maximizes over (τ₁, τ₂):

criterion	Task	Direction	What it measures
"auto" (default)	any	—	regression → rmse, binary → accuracy
"rmse"	regression	min	point-prediction RMSE on val
"accuracy"	binary	max	classification accuracy on val
"auc"	binary	max	ROC AUC on val
"cov_frob"	regression	min	relative Frobenius covariance error, ||Σ̂_pred − Σ̂_obs||_F / ||Σ̂_obs||_F
"sv_score"	regression	min	weighted L² distance between empirical semivariograms of val and prediction (gstools)

For the paper's KAUST Table 4 ablation (RMSE vs CovFrob vs SV_score selection), use these criteria directly. For domain-specific ground-truth covariance (e.g. a known Matérn model), fall back to AdapterTuner with a custom evaluate_fn.

Option B — manual control (power users)

Bypasses tuning when you already have (τ₁, τ₂) or want direct control of the ADMM loop.

import torch
from spatial_adapter import (
    SpatialAdapter, SpatialAdapterConfig,
    SpatialBasisLearner, TrendModel,
)

trend = TrendModel(num_continuous_features=5, hidden_layer_sizes=[], n_locations=100)
basis = SpatialBasisLearner(num_locations=100, latent_dim=10)

adapter = SpatialAdapter(
    trend, basis, train_loader,
    val_cont=val_X, val_y=val_Y, locs=station_coords,
    config=SpatialAdapterConfig(),
    device=torch.device("cpu"),
    tau1=1.0, tau2=1.0,
)
adapter.pretrain_trend(epochs=5)
adapter.init_basis_dense()
adapter.run()  # ADMM optimization

Examples & paper experiments

End-to-end scripts, configs, and notebooks live under examples/. To reproduce the paper tables (data download, config → table mapping, expected output) see examples/experiments/README.md.

Project layout

• spatial_adapter/ — core library: models/, data/, metrics.py, prediction.py, tuning/, utils/, and cpp_extensions/ (pybind11 C++ kernels).
• examples/ — runnable experiments (experiments/) and baselines (baselines/stdk/).
• tests/ — pytest suite; see make test.
• data/ — external datasets (git-ignored; see data/README.md).

Development

make conda-env       # set up environment
make build-cpp       # build C++ extensions
make test            # run tests
make test-cov        # tests with HTML coverage

Citation

@misc{wang2026spatialadapterstructuredspatial,
      title={Spatial Adapter: Structured Spatial Decomposition and Closed-Form Covariance for Frozen Predictors},
      author={Wen-Ting Wang and Wei-Ying Wu and Hao-Yun Huang and Xuan-Chun Wang},
      year={2026},
      eprint={2605.11394},
      archivePrefix={arXiv},
      primaryClass={stat.ML},
      url={https://arxiv.org/abs/2605.11394},
}

License

MIT — see LICENSE.