# \`Optimization.LBFGS\` fails to converge while \`Optim.NelderMead()\` works

**URL:** <https://discourse.julialang.org/t/optimization-lbfgs-fails-to-converge-while-optim-neldermead-works/121016>\
**Category:** General Usage\
**Tags:** question, optim, optimization\
**Created:** [October 7, 2024, 3:52pm UTC](https://discourse.julialang.org/t/optimization-lbfgs-fails-to-converge-while-optim-neldermead-works/121016 "2024-10-07T15:52:03Z")\
**Posts on this page:** 1\
**Showing post:** 10

<div class="post-metadata">

**Author:** ![jling](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jling/32/212909_2.png) [@jling](https://discourse.julialang.org/u/jling)\
**Post date:** [October 8, 2024, 7:54am UTC](https://discourse.julialang.org/t/optimization-lbfgs-fails-to-converge-while-optim-neldermead-works/121016/10 "2024-10-08T07:54:29Z")

</div>

> [@roflmaostc](#):
>
> `r = * Status: failure (reached maximum number of iterations)`

thanks for the insight, so if I updated your code to increase iterations to 10^5:

```julia
    return Optim.optimize(F, p0, LBFGS(), Optim.Options(;iterations=10^5); autodiff=:forward)

```

I get

```julia
Status: failure (line search failed)

 * Candidate solution
    Final objective value: 9.802206e+01

 * Found with
    Algorithm: L-BFGS

```

btw, even with more iterations, the result from NelderMead and LBFGS don’t converge:

```julia
function optim_fit2(func::T, xs, ys, σs, p0; algo = LBFGS()) where T
    F = function (p)
        cs = func(xs, p)
        return chi2(ys, cs, σs)
    end

    return Optim.optimize(F, p0, algo, Optim.Options(;iterations=5000); autodiff=:forward)
end

sol_nm = optim_fit2(ATLAS_f_6p, xs, ys, sigmas, p0_6para; algo = NelderMead())
sol_lbfgs = optim_fit2(ATLAS_f_6p, xs, ys, sigmas, p0_6para; algo = LBFGS())

julia> sol_nm.minimum, sol_lbfgs.minimum
(98.51662613370482, 98.0220580738921)

julia> sol_nm.minimizer, sol_lbfgs.minimizer
([0.014343016762772673, 0.36918264249014077, 0.08258611548972156, -0.019076422764126248, -0.31125906069802134, -0.044992442492889535], [11207.052120386572, -913.9928401545511, 165.74801872441768, 91.61206638696663, 17.418590874571905, 1.1299718078901382])

```

if we use BFGS + stopping criteria from [Connection between BFGS and ROOT.Minuit. Stopping criteria - #4 by Yuan-Ru-Lin](https://discourse.julialang.org/t/connection-between-bfgs-and-root-minuit-stopping-criteria/48729/4)

which is yet another set of `minimizer`…

```julia
julia> sol_lbfgs.minimizer |> print
[3.724592263478385, 0.7652684260382869, 4.556910181502994, 1.2983875079831064, -0.1450263191617602, -0.037556051055012134]

```

I think this is consistent with what @ChrisRackauckas said about the line search in Optim is “bad” (not sure what it means exactly).

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