Optimistix

Optimistix is a JAX library for nonlinear solvers, including root finding, minimisation, fixed points, and least squares. It features highly modular optimisers, interoperable solvers (e.g., converting root find problems to least squares), PyTree-based state management, fast compilation and runtimes, and deep integration with the JAX ecosystem for features like autodiff, autoparallelism, and GPU/TPU support. As of version 0.1.0, it requires Python 3.11+ and is under active, rapid development with frequent updates.