How to make Optim's optimize work for scalars

Specific Domains Optimization (Mathematical)
2

I am not sure you are aware of the possible pitfalls. Curiously, multivariate methods can break down in surprising ways in 1D, and can easily yield suboptimal performance. Optim also has GoldenSection(), see

That said, you can always write a wrapper like

using Optim

function univariate_optimize(f, x0, args...; kwargs...)
    opt = Optim.optimize(x -> f(x[1]), [x0], args...; kwargs...)
    @assert Optim.converged(opt)
    Optim.minimizer(opt)[1]
end

univariate_optimize(x -> abs2(x), 1.0, BFGS(); autodiff = :forward)

You just have to make a decision about what to extract from Optim.MultivariateOptimizationResults, or write a conversion routine to Optim.UnivariateOptimizationResults.

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