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Missing a leg? A blowtorch? You might want to check with Los Angeles Metro

Los Angeles Times

Things to Do in L.A. Tap to enable a layout that focuses on the article. Various items at the Metro Lost & Found office on March 5, 2026. This is read by an automated voice. Please report any issues or inconsistencies here . If you've ever lost something valuable on a Metro bus or train and assumed it was gone forever, take heart: There is a system for reuniting riders with their possessions.










Discrete Adjoint Matching

So, Oswin, Karrer, Brian, Fan, Chuchu, Chen, Ricky T. Q., Liu, Guan-Horng

arXiv.org Machine Learning

Computation methods for solving entropy-regularized reward optimization -- a class of problems widely used for fine-tuning generative models -- have advanced rapidly. Among those, Adjoint Matching (AM, Domingo-Enrich et al., 2025) has proven highly effective in continuous state spaces with differentiable rewards. Transferring these practical successes to discrete generative modeling, however, remains particularly challenging and largely unexplored, mainly due to the drastic shift in generative model classes to discrete state spaces, which are nowhere differentiable. In this work, we propose Discrete Adjoint Matching (DAM) -- a discrete variant of AM for fine-tuning discrete generative models characterized by Continuous-Time Markov Chains, such as diffusion-based large language models. The core of DAM is the introduction of discrete adjoint-an estimator of the optimal solution to the original problem but formulated on discrete domains-from which standard matching frameworks can be applied. This is derived via a purely statistical standpoint, in contrast to the control-theoretic viewpoint in AM, thereby opening up new algorithmic opportunities for general adjoint-based estimators. We showcase DAM's effectiveness on synthetic and mathematical reasoning tasks.