Information-Preserving Domain Transfer with Unlabeled Data in Misspecified Simulation-Based Inference

TL;DR

SPIN is a novel SBI framework that uses unlabeled real-world data to improve Bayesian inference under model misspecification by preserving parameter-relevant information during domain transfer.

Contribution

It introduces a parameter-relevant information-preserving domain transfer method that leverages unlabeled, unpaired real-world observations for improved inference.

Findings

SPIN enhances real-world posterior inference in synthetic and physical benchmarks.

The method's benefits increase with higher model misspecification.

SPIN does not require real-world parameter labels or paired data during testing.

Abstract

Simulation-based inference (SBI) provides amortized Bayesian parameter inference from simulator-generated data without requiring explicit likelihood evaluation. Its reliability can degrade under model misspecification, where real-world observations are not well represented by the simulator used for training. Existing methods using unlabeled real-world data often align simulated and real-world data distributions, but marginal alignment alone does not directly preserve parameter-relevant information needed for posterior inference. We propose SPIN, an SBI framework with parameter-relevant information-preserving domain transfer using unlabeled, unpaired real-world observations. During training, SPIN translates labeled simulator observations toward the real-world domain and back to the simulator domain, using the original simulator labels to encourage domain transfer that preserves parameter-relevant mutual information. At test time, the learned real-to-simulator transport maps real-world observations into the simulator domain for posterior inference, without requiring real-world parameter labels or paired real--simulator observations. Across controlled synthetic and physical real-world benchmarks, SPIN improves real-world posterior inference, with the improvement becoming clearer as misspecification increases.