Hi, PR 8431 is ready for review, IMHO. https://github.com/scipy/scipy/pull/8431 This PR adds a Cython API for root-finding of scalar functions in Optimize. It exposes brentq, brenth, ridder, bisect, newton, secant, and halley with 3 different callback signatures, two which are safe with Cython `nogil` which allows them to be called with Cython `prange`. this PR is a follow on to #8357, and allows efficient looping from C of large arrays with the same callback using any of the scalar-function root finders. I would appreciate your comments. Best, Mark -- Mark Mikofski, PhD (2005) *Fiat Lux*