# Type instabilities when using broadcasting with splat operator
**URL:** https://discourse.julialang.org/t/type-instabilities-when-using-broadcasting-with-splat-operator/116698
**Category:** Performance
**Tags:** code\_warntype, type-stability
**Created:** [July 6, 2024, 3:01pm UTC](https://discourse.julialang.org/t/type-instabilities-when-using-broadcasting-with-splat-operator/116698 "2024-07-06T15:01:57Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@danielelamberto](https://discourse.julialang.org/u/danielelamberto)
#### Post date: [July 6, 2024, 3:01pm UTC](https://discourse.julialang.org/t/type-instabilities-when-using-broadcasting-with-splat-operator/116698/1 "2024-07-06T15:01:57Z")
Hi,
I’m trying to optimize my code and I noticed a type instability when using broadcasting together with the splat operator, as in the following code:
```julia
function f(x, p1, p2)
return x * p1 + p2
end
x = rand(1000)
p1 = 2.0
p2 = 3.0
p0 = [p1, p2]
f.(x, p0...)
@code_warntype f.(x, p0...)
```
and I get the following
```julia
MethodInstance for (::var"##dotfunction#389#20")(::Vector{Float64}, ::Vector{Float64})
from (::var"##dotfunction#389#20")(x1, x2) @ Main none:0
Arguments
#self#::Core.Const(var"##dotfunction#389#20"())
x1::Vector{Float64}
x2::Vector{Float64}
Body::Any
1 ─ %1 = Core.tuple(Main.f, x1)::Tuple{typeof(f), Vector{Float64}}
│ %2 = Core._apply_iterate(Base.iterate, Base.broadcasted, %1, x2)::Any
│ %3 = Base.materialize(%2)::Any
└── return %3
```
On the contrary, if I insert the elements individually, everything is fine.
I would prefer to use the splat operator since I have a lot of parameters to insert.
---
### Author:  [@Tarny\_GG\_Channie](https://discourse.julialang.org/u/Tarny_GG_Channie)
#### Post date: [July 6, 2024, 3:14pm UTC](https://discourse.julialang.org/t/type-instabilities-when-using-broadcasting-with-splat-operator/116698/2 "2024-07-06T15:14:58Z")
Your p0 is a vector, which means the “…” operator doesn’t know how many arguments there are, which means it dispatches to an unknown method of f, which means type instability. Change p0 to a tuple and you solve the issue.
---
### Author:  [@danielelamberto](https://discourse.julialang.org/u/danielelamberto)
#### Post date: [July 6, 2024, 4:03pm UTC](https://discourse.julialang.org/t/type-instabilities-when-using-broadcasting-with-splat-operator/116698/3 "2024-07-06T16:03:39Z")
Thanks, it worked perfectly!