Picasso's GPU and CPU curve fitters are derived from Gpufit
(https://github.com/gpufit/Gpufit). Its Levenberg-Marquardt driver, its
Gauss-Jordan solve, its least-squares and Poisson maximum-likelihood estimators
and its Gaussian and cubic-spline PSF models were ported to Python/numba in

    picasso/fitting/splinefit.py       CPU cubic-spline fitting
    picasso/fitting/splinefit_cuda.py  CUDA cubic-spline fitting
    picasso/fitting/gaussfit_cuda.py   CUDA Gaussian fitting
    picasso/fitting/lmfit_cuda.py      shared CUDA Levenberg-Marquardt
                                       machinery

Picasso no longer links against or redistributes the Gpufit binary, but those
modules remain derivative works of its source, so its licence is reproduced
below in full.

Cite: Przybylski, A., Thiel, B., Keller-Findeisen, J., Stock, B. & Bates, M.
"Gpufit: An open-source toolkit for GPU-accelerated curve fitting."
Scientific Reports 7, 15722 (2017). https://doi.org/10.1038/s41598-017-15313-9

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MIT License

Copyright (c) 2017 Mark Bates, Adrian Przybylski, Björn Thiel, and Jan Keller-Findeisen

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
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copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

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SOFTWARE.
