# How to control output type with Flux?
**URL:** https://discourse.julialang.org/t/how-to-control-output-type-with-flux/98770
**Category:** General Usage
**Created:** [May 12, 2023, 10:16pm UTC](https://discourse.julialang.org/t/how-to-control-output-type-with-flux/98770 "2023-05-12T22:16:15Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@erlebach](https://discourse.julialang.org/u/erlebach)
#### Post date: [May 12, 2023, 10:16pm UTC](https://discourse.julialang.org/t/how-to-control-output-type-with-flux/98770/1 "2023-05-12T22:16:16Z")
Here is a MWE:
```julia
using Flux
function NeuralNetwork(; nb_in=1, nb_out=1, layer_size=8, nb_hid_layers=1)
# Note the use of Any[] since the Dense layers are of different types
layers = Any[Flux.Dense(nb_in => layer_size, tanh)]
push!(layers, Flux.Dense(layer_size => nb_out))
return Chain(layers...)
end
# Set up Neural Netoork (input layer, hidden layers, output layer)
model_univ = NeuralNetwork(nb_in=9, nb_out=9, layer_size=8, nb_hid_layers=0)
p_model, re = Flux.destructure(model_univ)
p_model = zeros(Float64, length(p_model))
input = rand(Float64, 9)
model_univ(input)
```
The last line produces output of type `Float32`, even though the weights `p_model` is of type `Float64`. I cannot figure out how to generate output data of type `Float64`. Any help is appreciated.
---
### Author:  [@mcabbott](https://discourse.julialang.org/u/mcabbott)
#### Post date: [May 12, 2023, 10:23pm UTC](https://discourse.julialang.org/t/how-to-control-output-type-with-flux/98770/2 "2023-05-12T22:23:06Z")
Flux now standardises on the eltype of the weight arrays. This is because accidental promotion to Float64 was a very common huge performance bug. Your network has Float32 weights because this is the default of `Dense` (and all other layers).
If you want to run the network with Float64 everywhere, then you want `f64(model)` or `Chain(layers...) |> f64`. Just once, after construction.
If you want Float64 numbers out of a network with Float32 weights, you could for instance write `Chain(layers..., f64)`. The input should then ideally be Float32 (it will be converted if not).
---
### Author:  [@erlebach](https://discourse.julialang.org/u/erlebach)
#### Post date: [May 12, 2023, 10:28pm UTC](https://discourse.julialang.org/t/how-to-control-output-type-with-flux/98770/3 "2023-05-12T22:28:26Z")
Thanks! I never would have figured this out. I am debugging code, and this is a temporary phase.
---
### Author:  [@mcabbott](https://discourse.julialang.org/u/mcabbott)
#### Post date: [May 12, 2023, 10:34pm UTC](https://discourse.julialang.org/t/how-to-control-output-type-with-flux/98770/4 "2023-05-12T22:34:34Z")
The first time I run this, it prints a warning:
```julia
julia> model_univ(input)
┌ Warning: Layer with Float32 parameters got Float64 input.
│ The input will be converted, but any earlier layers may be very slow.
│ layer = Dense(9 => 8, tanh) # 80 parameters
│ summary(x) = "9-element Vector{Float64}"
└ @ Flux ~/.julia/packages/Flux/Nzh8J/src/layers/stateless.jl:50
9-element Vector{Float32}:
-0.19098403
0.20039776
0.031824134
```
Maybe this should suggest `f64`. It is certainly easy to miss but making it print every time would be pretty noisy.
Is there an obvious place in the documentation to mention this?