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that is an algorithm for a different problem; here we are looking for a zero, not an extremum, and we want to find all the zeroes (in a two-dimensional plane, so there are usually infinitely many zeroes), not just one of them

perhaps there is a way to apply it to this problem that is obvious to you but not to me

with autodiff we can use a zero-finding algorithm (even one that isn't derivative-free) to find extrema, but i don't know how you'd go about using an extremum-finding algorithm to find zeroes. the first step would seem to be quadrature? but that sounds impractical




The algoithm itself is about the use of golden ratio for interval search.

One can use subdivision, other can use ternary division. And another one can use golden ratio.


as i understand it, the advantage of golden-section search is that, to search for a minimum rather than a zero, you need to in some sense interpolate a parabola rather than a line, so you need three points rather than two, and you'd like them to be somewhat evenly spaced. i don't fully understand why the golden section is better for this than just dividing the interval between the two lowest points in half, but it's definitely an algorithm to solve a different problem




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