# Memory allocations in Flux evaluation/training (w/MVE)

**URL:** <https://discourse.julialang.org/t/memory-allocations-in-flux-evaluation-training-w-mve/137175>\
**Category:** Machine Learning\
**Tags:** memory-allocation, flux\
**Created:** [May 18, 2026, 9:29pm UTC](https://discourse.julialang.org/t/memory-allocations-in-flux-evaluation-training-w-mve/137175 "2026-05-18T21:29:26Z")\
**Posts on this page:** 1\
**Showing post:** 32

<div class="post-metadata">

**Author:** ![CrashBurnRepeat](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/crashburnrepeat/32/4460_2.png) [@CrashBurnRepeat](https://discourse.julialang.org/u/CrashBurnRepeat)\
**Post date:** [June 1, 2026, 11:15pm UTC](https://discourse.julialang.org/t/memory-allocations-in-flux-evaluation-training-w-mve/137175/32 "2026-06-01T23:15:01Z")

</div>

Edit: I just found that I’m not the first to have this issue, it seems to be specific to the Adam optimizer. Still, the [solution from the previous issue](https://discourse.julialang.org/t/reactant-jl-and-lux-jl-dont-work-with-adam-optimiser/132278) was to delete and redownload all dependencies. I’m trying this on a new notebook, so it should be “fresh”?

Edit 2: Just changed to Descent and it works. I guess this is just a data point for the Adam issue?

So when trying to use `@compile` to capture the whole updating step with a simpler loss function, I’m running into a new error. The code for reference is

```julia-auto
opt = Flux.setup(Adam(), m)
ora = opt|>dev

function f_grad(f, m, z)
	Enzyme.gradient(Enzyme.Reverse, f, m, z) |> first
end

function ud(f, m, z, opt)
	gs = f_grad(f, m, z)
	Optimisers.update(opt, m, gs)
end

@compile ud(𝒱ₙₙ, mra, zra, ora)

```

where `m` is the model and `z` is some random data, with `mra` and `zra` being the same objects moved to RArrays. The error I’m getting is

```julia-auto
MethodError: no method matching Float32(::Reactant.TracedRNumber{Float32})

The type `Float32` exists, but no method is defined for this combination of argument types when trying to construct it.

Closest candidates are:

  (::Type{T})(::T) where T<:Number

   @ Core boot.jl:965

  Float32(::IrrationalConstants.Halfπ)

   @ IrrationalConstants ~/.julia/packages/IrrationalConstants/RokwY/src/macro.jl:112

  Float32(::IrrationalConstants.Logten)

   @ IrrationalConstants ~/.julia/packages/IrrationalConstants/RokwY/src/macro.jl:112

  ...

```

with the full stack trace

```julia-auto
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(convert), ::Type{…}, ::Reactant.TracedRNumber{…}) ...show types...
from 
utils.jl
cvt1
from 
essentials.jl:612
ntuple
from 
ntuple.jl:51
convert
from 
essentials.jl:614
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(convert), ::Type{…}, ::Tuple{…}) ...show types...
from 
utils.jl
cvt1
from 
essentials.jl:612
ntuple
from 
ntuple.jl:52
convert
from 
essentials.jl:614
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(convert), ::Type{…}, ::Tuple{…}) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(setproperty!), ::Optimisers.Leaf{…}, ::Symbol, ::Tuple{…}) ...show types...
from 
utils.jl
#_update!#11
from 
interface.jl:96
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::Optimisers.var"##_update!#11", ::IdDict{…}, ::IdDict{…}, ::typeof(Optimisers._update!), ::Optimisers.Leaf{…}, ::Reactant.TracedRArray{…}) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(Core.kwcall), ::@NamedTuple{…}, ::typeof(Optimisers._update!), ::Optimisers.Leaf{…}, ::Reactant.TracedRArray{…}) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::Optimisers.var"#9#10"{…}, ::Optimisers.Leaf{…}, ::Reactant.TracedRArray{…}) ...show types...
from 
utils.jl
map
from 
tuple.jl:389
map
from 
namedtuple.jl:263
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(map), ::Optimisers.var"#9#10"{…}, ::@NamedTuple{…}, ::@NamedTuple{…}) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(Optimisers.mapvalue), ::Optimisers.var"#9#10"{…}, ::@NamedTuple{…}, ::@NamedTuple{…}) ...show types...
from 
utils.jl
#_update!#7
from 
interface.jl:85
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::Optimisers.var"##_update!#7", ::IdDict{…}, ::IdDict{…}, ::typeof(Optimisers._update!), ::@NamedTuple{…}, ::Flux.Conv{…}) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(Core.kwcall), ::@NamedTuple{…}, ::typeof(Optimisers._update!), ::@NamedTuple{…}, ::Flux.Conv{…}) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::Optimisers.var"#9#10"{…}, ::@NamedTuple{…}, ::Flux.Conv{…}) ...show types...
from 
utils.jl
map
from 
tuple.jl:389
mapvalue
from 
utils.jl:2
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(Optimisers.mapvalue), ::Optimisers.var"#9#10"{…}, ::Tuple{…}, ::Tuple{…}) ...show types...
from 
utils.jl
#_update!#7
from 
interface.jl:85
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::Optimisers.var"##_update!#7", ::IdDict{…}, ::IdDict{…}, ::typeof(Optimisers._update!), ::Tuple{…}, ::Tuple{…}) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(Core.kwcall), ::@NamedTuple{…}, ::typeof(Optimisers._update!), ::Tuple{…}, ::Tuple{…}) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::Optimisers.var"#9#10"{…}, ::Tuple{…}, ::Tuple{…}) ...show types...
from 
utils.jl
map
from 
tuple.jl:385
map
from 
namedtuple.jl:263
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(map), ::Optimisers.var"#9#10"{…}, ::@NamedTuple{…}, ::@NamedTuple{…}) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(Optimisers.mapvalue), ::Optimisers.var"#9#10"{…}, ::@NamedTuple{…}, ::@NamedTuple{…}) ...show types...
from 
utils.jl
#_update!#7
from 
interface.jl:85
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::Optimisers.var"##_update!#7", ::IdDict{…}, ::IdDict{…}, ::typeof(Optimisers._update!), ::@NamedTuple{…}, ::Flux.Chain{…}) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(Core.kwcall), ::@NamedTuple{…}, ::typeof(Optimisers._update!), ::@NamedTuple{…}, ::Flux.Chain{…}) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::Optimisers.var"#9#10"{…}, ::@NamedTuple{…}, ::Flux.Chain{…}) ...show types...
from 
utils.jl
map
from 
tuple.jl:386
mapvalue
from 
utils.jl:2
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(Optimisers.mapvalue), ::Optimisers.var"#9#10"{…}, ::Tuple{…}, ::Tuple{…}) ...show types...
from 
utils.jl
#_update!#7
from 
interface.jl:85
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::Optimisers.var"##_update!#7", ::IdDict{…}, ::IdDict{…}, ::typeof(Optimisers._update!), ::Tuple{…}, ::Tuple{…}) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(Core.kwcall), ::@NamedTuple{…}, ::typeof(Optimisers._update!), ::Tuple{…}, ::Tuple{…}) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::Optimisers.var"#9#10"{…}, ::Tuple{…}, ::Tuple{…}) ...show types...
from 
utils.jl
map
from 
tuple.jl:385
map
from 
namedtuple.jl:263
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(map), ::Optimisers.var"#9#10"{…}, ::@NamedTuple{…}, ::@NamedTuple{…}) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(Optimisers.mapvalue), ::Optimisers.var"#9#10"{…}, ::@NamedTuple{…}, ::@NamedTuple{…}) ...show types...
from 
utils.jl
#_update!#7
from 
interface.jl:85
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::Optimisers.var"##_update!#7", ::IdDict{…}, ::IdDict{…}, ::typeof(Optimisers._update!), ::@NamedTuple{…}, ::Flux.Chain{…}) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(Core.kwcall), ::@NamedTuple{…}, ::typeof(Optimisers._update!), ::@NamedTuple{…}, ::Flux.Chain{…}) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::Optimisers.var"#9#10"{…}, ::@NamedTuple{…}, ::Flux.Chain{…}) ...show types...
from 
utils.jl
map
from 
tuple.jl:386
map
from 
namedtuple.jl:263
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(map), ::Optimisers.var"#9#10"{…}, ::@NamedTuple{…}, ::@NamedTuple{…}) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(Optimisers.mapvalue), ::Optimisers.var"#9#10"{…}, ::@NamedTuple{…}, ::@NamedTuple{…}) ...show types...
from 
utils.jl
#_update!#7
from 
interface.jl:85
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::Optimisers.var"##_update!#7", ::IdDict{…}, ::IdDict{…}, ::typeof(Optimisers._update!), ::@NamedTuple{…}, ::gan_model) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(Core.kwcall), ::@NamedTuple{…}, ::typeof(Optimisers._update!), ::@NamedTuple{…}, ::gan_model) ...show types...
from 
utils.jl
update!
from 
interface.jl:77
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(Optimisers.update!), ::@NamedTuple{…}, ::gan_model, ::gan_model) ...show types...
from 
utils.jl
call_with_reactant
from 
call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(Optimisers.update), ::@NamedTuple{…}, ::gan_model, ::gan_model) ...show types...
from 
utils.jl
call_with_reactant
from 

```

It feels like it should be fairly straighforward, but perhaps I’m missing something here?

---

_[View the full topic](https://discourse.julialang.org/t/memory-allocations-in-flux-evaluation-training-w-mve/137175)._