# Avoid allocations in one-dimensional Optim when target expects vector
**URL:** https://discourse.julialang.org/t/avoid-allocations-in-one-dimensional-optim-when-target-expects-vector/131159
**Category:** General Usage
**Tags:** allocations
**Created:** [July 29, 2025, 7:40am UTC](https://discourse.julialang.org/t/avoid-allocations-in-one-dimensional-optim-when-target-expects-vector/131159 "2025-07-29T07:40:32Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@JADekker](https://discourse.julialang.org/u/JADekker)
#### Post date: [July 29, 2025, 7:40am UTC](https://discourse.julialang.org/t/avoid-allocations-in-one-dimensional-optim-when-target-expects-vector/131159/1 "2025-07-29T07:40:32Z")
Hi, I’m in an optimization situation where I have an objective function that expects a vector input, but the optimization problem is over just one variable, so I’d like to use Brent’s algorithm. To make it compatible with my function, I simply use `x -> test_vector([x])` in the below, which seems to add a lot of allocations. Is there a way to avoid this? (In my use-case, I have something that looks like `test_vector`, not `test_scalar`). See below MWE
```julia-auto
using BenchmarkTools
using Optim
test_scalar(x::Real) = x^2
function optims_scalar()
ress = 0.
for i in 1:10
ress += Optim.optimize(test_scalar, 0.0, 1.0, Brent()).minimizer
end
return ress
end
test_vector(x::AbstractVector) = @inbounds x[1]^2
function optims_vector()
ress = 0.
for i in 1:10
ress += Optim.optimize(x -> test_vector([x]), 0.0, 1.0, Brent()).minimizer[1]
end
return ress
end
function run_tests()
display(@benchmark optims_scalar())
display(@benchmark optims_vector())
end
run_tests()
```
gives
```julia-auto
BenchmarkTools.Trial: 10000 samples with 1 evaluation per sample.
Range (min … max): 12.000 μs … 49.500 μs ┊ GC (min … max): 0.00% … 0.00%
Time (median): 12.125 μs ┊ GC (median): 0.00%
Time (mean ± σ): 12.383 μs ± 1.590 μs ┊ GC (mean ± σ): 0.00% ± 0.00%
█▇▆▄▄▃▁▂▃▂ ▂
████████████▇▇▇▆▅▆▅▆▅▅▃▆▄▄▃▄▅▅▄▅▅▄▅▃▄▆▁▅▄▅▅▄▃▄▄▁▃▆▅▅▅▅▅▆▅▆▇ █
12 μs Histogram: log(frequency) by time 17.4 μs <
Memory estimate: 1.72 KiB, allocs estimate: 20.
BenchmarkTools.Trial: 10000 samples with 1 evaluation per sample.
Range (min … max): 17.416 μs … 32.571 ms ┊ GC (min … max): 0.00% … 99.88%
Time (median): 18.334 μs ┊ GC (median): 0.00%
Time (mean ± σ): 22.684 μs ± 326.642 μs ┊ GC (mean ± σ): 16.69% ± 2.19%
▇█ ▁ ▄▂
▅██▇▇█▅▄▃▂██▆▅▇▄▃▃▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▁▂▂▂▂ ▃
17.4 μs Histogram: frequency by time 27 μs <
Memory estimate: 47.97 KiB, allocs estimate: 760.
```
fwiw, I’m on v1.10.4 for compatibility reasons
---
### Author:  [@yolhan\_mannes](https://discourse.julialang.org/u/yolhan_mannes)
#### Post date: [July 29, 2025, 8:09am UTC](https://discourse.julialang.org/t/avoid-allocations-in-one-dimensional-optim-when-target-expects-vector/131159/2 "2025-07-29T08:09:33Z")
Can you try using StaticArrays.jl and just do `SA[x]` instead, in 1.12 everything is fine but it may be because of the compiler improvment. BTW if you can write your problem as a system of Optim its far better than solving for each i like that
---
### Author:  [@JADekker](https://discourse.julialang.org/u/JADekker)
#### Post date: [July 29, 2025, 8:20am UTC](https://discourse.julialang.org/t/avoid-allocations-in-one-dimensional-optim-when-target-expects-vector/131159/3 "2025-07-29T08:20:02Z")
I’ll try the static version in a bit. What do you mean with a system of Optim?
---
### Author:  [@yolhan\_mannes](https://discourse.julialang.org/u/yolhan_mannes)
#### Post date: [July 29, 2025, 8:22am UTC](https://discourse.julialang.org/t/avoid-allocations-in-one-dimensional-optim-when-target-expects-vector/131159/4 "2025-07-29T08:22:01Z")
I mean if you can minimize a vector instead, the only reason you couldn’t is if you need previous results
---
### Author:  [@JADekker](https://discourse.julialang.org/u/JADekker)
#### Post date: [July 29, 2025, 8:25am UTC](https://discourse.julialang.org/t/avoid-allocations-in-one-dimensional-optim-when-target-expects-vector/131159/5 "2025-07-29T08:25:04Z")
In my use case, each ‘i’ actually gets a slightly different function, so I’m afraid that won’t work for me
---
### Author:  [@JADekker](https://discourse.julialang.org/u/JADekker)
#### Post date: [July 29, 2025, 8:48am UTC](https://discourse.julialang.org/t/avoid-allocations-in-one-dimensional-optim-when-target-expects-vector/131159/6 "2025-07-29T08:48:35Z")
Works like a charm, both in my MWE and in the code where I need it! Thanks! (Saves me about 5% runtime and 6% reduction in memory allocation size in my actual code, which is a nice improvement for adding two letters…)