# Can I modify Flux parameters manually?

**URL:** <https://discourse.julialang.org/t/can-i-modify-flux-parameters-manually/54344>\
**Category:** Machine Learning\
**Created:** [January 31, 2021, 8:30pm UTC](https://discourse.julialang.org/t/can-i-modify-flux-parameters-manually/54344 "2021-01-31T20:30:11Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![DevJac](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@DevJac](https://discourse.julialang.org/u/DevJac)\
**Post date:** [January 31, 2021, 8:30pm UTC](https://discourse.julialang.org/t/can-i-modify-flux-parameters-manually/54344/1 "2021-01-31T20:30:11Z")

</div>

I want to be able to manually modify my Flux parameters, but when I have a `Zygote.Params` object, I can’t seem to change anything about it. I am trying to average the parameters of two networks that are the same shape (Polyak averaging).

Consider this REPL:

```julia
julia> using Flux

julia> nn = Dense(3, 3)
Dense(3, 3)

julia> params(nn)
Params([Float32[-0.8835063 0.7971344 -0.3184507; -0.38867068 -0.966625 -0.118569136; -0.39296985 -0.4625342 0.55543184], Float32[0.0, 0.0, 0.0]])

julia> params(nn)[1] *= 0
ERROR: MethodError: no method matching setindex!(::Zygote.Params, ::Array{Float32,2}, ::Int64)
Stacktrace:
 [1] top-level scope at REPL[4]:1

julia> the_params = params(nn)[1]
3×3 Array{Float32,2}:
 -0.883506 0.797134 -0.318451
 -0.388671 -0.966625 -0.118569
 -0.39297 -0.462534 0.555432

julia> typeof(the_params)
Array{Float32,2}

julia> the_params *= 0
3×3 Array{Float32,2}:
 -0.0 0.0 -0.0
 -0.0 -0.0 -0.0
 -0.0 -0.0 0.0

julia> the_params
3×3 Array{Float32,2}:
 -0.0 0.0 -0.0
 -0.0 -0.0 -0.0
 -0.0 -0.0 0.0

julia> params(nn)
Params([Float32[-0.8835063 0.7971344 -0.3184507; -0.38867068 -0.966625 -0.118569136; -0.39296985 -0.4625342 0.55543184], Float32[0.0, 0.0, 0.0]])

julia> params(nn)[1]
3×3 Array{Float32,2}:
 -0.883506 0.797134 -0.318451
 -0.388671 -0.966625 -0.118569
 -0.39297 -0.462534 0.555432

```

As you can see, I either cannot change the parameters. Or, if I do manage to get a hold of something I can change, it’s just a copy and doesn’t actually change the parameters.

Is there a way I can manually change the parameters?

---

<div class="post-metadata">

**Author:** ![DevJac](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@DevJac](https://discourse.julialang.org/u/DevJac)\
**Post date:** [January 31, 2021, 8:45pm UTC](https://discourse.julialang.org/t/can-i-modify-flux-parameters-manually/54344/2 "2021-01-31T20:45:38Z")

</div>

I needed to use `.*=` to “broadcast” the change instead of `*=`.

Consider:

```julia
julia> using Flux

julia> nn = Dense(3, 3)
Dense(3, 3)

julia> params(nn)
Params([Float32[-0.1867888 0.45788264 0.42513847; 0.29547477 0.8505957 0.6445496; 0.31435943 -0.9087379 0.5611925], Float32[0.0, 0.0, 0.0]])

julia> params(nn)[1] .*= 0
3×3 Array{Float32,2}:
 -0.0 0.0 0.0
  0.0 0.0 0.0
  0.0 -0.0 0.0

julia> params(nn)
Params([Float32[-0.0 0.0 0.0; 0.0 0.0 0.0; 0.0 -0.0 0.0], Float32[0.0, 0.0, 0.0]])

```