# Use of Reactant.jl on existing framework

**URL:** <https://discourse.julialang.org/t/use-of-reactant-jl-on-existing-framework/135261>\
**Category:** General Usage\
**Tags:** reactant\
**Created:** [January 25, 2026, 11:43pm UTC](https://discourse.julialang.org/t/use-of-reactant-jl-on-existing-framework/135261 "2026-01-25T23:43:32Z")\
**Posts on this page:** 10\
**Page:** 1

<div class="post-metadata">

**Author:** ![albertomercurio](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/albertomercurio/32/27051_2.png) [@albertomercurio](https://discourse.julialang.org/u/albertomercurio)\
**Post date:** [January 25, 2026, 11:43pm UTC](https://discourse.julialang.org/t/use-of-reactant-jl-on-existing-framework/135261/1 "2026-01-25T23:43:32Z")

</div>

Hello,

I have some generic function that tests some functionalities of a package. The function does something like this

```julia-auto
function shared_function(T, array_type)
    x = rand(T, 10, 10)
    dx = array_type(x)
    @test some_function(dx) = some_function(x)
end

```

In this way I can test many backends by just changing `array_type` to e.g. `Array`, `CuArray`, `MtlArray`, `ConcreteRArray`.

However, Reactant.jl need to compile the function first

```julia-auto
comp_f = @compile some_function(dx)
@test comp_f(dx) == some_function(x)

```

How should I manage this? Should I really put `@compile` to all the functions? This seems to be quite annoying.

---

<div class="post-metadata">

**Author:** ![Tortar](https://avatars.discourse-cdn.com/v4/letter/t/6bbea6/32.png) [@Tortar](https://discourse.julialang.org/u/Tortar)\
**Post date:** [January 26, 2026, 12:13am UTC](https://discourse.julialang.org/t/use-of-reactant-jl-on-existing-framework/135261/2 "2026-01-26T00:13:23Z")

</div>

Just want to say that I have the same inquiry of @albertomercurio for the same exact motivation 🙂

---

<div class="post-metadata">

**Author:** ![yolhan\_mannes](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/yolhan_mannes/32/220485_2.png) [@yolhan\_mannes](https://discourse.julialang.org/u/yolhan_mannes)\
**Post date:** [January 26, 2026, 12:17am UTC](https://discourse.julialang.org/t/use-of-reactant-jl-on-existing-framework/135261/3 "2026-01-26T00:17:45Z")

</div>

You could just do `@jit` for test that’s completely ok

---

<div class="post-metadata">

**Author:** ![albertomercurio](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/albertomercurio/32/27051_2.png) [@albertomercurio](https://discourse.julialang.org/u/albertomercurio)\
**Post date:** [January 26, 2026, 12:39am UTC](https://discourse.julialang.org/t/use-of-reactant-jl-on-existing-framework/135261/4 "2026-01-26T00:39:33Z")

</div>

It doesn’t seem to work

```julia-auto
function test_fun(T, array_type)
    x = rand(T, 100)
    dx = array_type(x)
    @test sum(dx) == sum(x)
end

```

```julia-auto
julia> test_fun(Float32, Array)
Test Passed

julia> test_fun(Float32, Reactant.to_rarray)
Test Failed at REPL[9]:4
  Expression: sum(dx) == sum(x)
   Evaluated: ConcretePJRTNumber{Float32, 1}(47.982807f0) == 47.98281f0

ERROR: There was an error during testing

julia> test_fun_compiled = @compile test_fun(Float32, Reactant.to_rarray)
ERROR: Cannot convert TracedRArray to ConcreteArray
Stacktrace:
  [1] call_with_reactant(::Reactant.EnsureReturnType{Union{}}, ::typeof(error), ::String)
    @ Reactant ~/.julia/packages/Reactant/AO3KW/src/utils.jl:1064
  [2] call_with_reactant(::Reactant.EnsureReturnType{…}, ::typeof(Reactant.to_rarray_internal), ::Reactant.TracedRArray{…}, ::Type{…}, ::Reactant.Sharding.NoSharding, ::Val{…}, ::Nothing, ::Nothing)
    @ Reactant ~/.julia/packages/Reactant/AO3KW/src/utils.jl:1064
  [3] #to_rarray#153
    @ ~/.julia/packages/Reactant/AO3KW/src/Tracing.jl:2050 [inlined]
  [4] to_rarray
    @ ~/.julia/packages/Reactant/AO3KW/src/Tracing.jl:2040 [inlined]
  [5] test_fun
    @ ./REPL[9]:3
  [6] call_with_reactant(::typeof(test_fun), ::Type{Float32}, ::typeof(Reactant.to_rarray))
    @ Reactant ~/.julia/packages/Reactant/AO3KW/src/utils.jl:1064
  [7] make_mlir_fn(f::typeof(test_fun), args::Tuple{…}, kwargs::@NamedTuple{}, name::String, concretein::Bool; toscalar::Bool, return_dialect::Symbol, args_in_result::Symbol, construct_function_without_args::Bool, do_transpose::Bool, within_autodiff::Bool, input_shardings::Nothing, output_shardings::Nothing, runtime::Val{…}, verify_arg_names::Nothing, argprefix::Symbol, resprefix::Symbol, resargprefix::Symbol, num_replicas::Int64, optimize_then_pad::Bool)
    @ Reactant.TracedUtils ~/.julia/packages/Reactant/AO3KW/src/TracedUtils.jl:355
  [8] make_mlir_fn
    @ ~/.julia/packages/Reactant/AO3KW/src/TracedUtils.jl:284 [inlined]
  [9] compile_mlir!(mod::Reactant.MLIR.IR.Module, f::typeof(test_fun), args::Tuple{…}, compile_options::CompileOptions, callcache::Dict{…}, sdycache::Dict{…}, sdygroupidcache::Tuple{…}; fn_kwargs::@NamedTuple{}, backend::String, runtime::Val{…}, legalize_stablehlo_to_mhlo::Bool, client::Reactant.XLA.PJRT.Client, kwargs::@Kwargs{})
    @ Reactant.Compiler ~/.julia/packages/Reactant/AO3KW/src/Compiler.jl:1740
 [10] compile_mlir!
    @ ~/.julia/packages/Reactant/AO3KW/src/Compiler.jl:1702 [inlined]
 [11] compile_xla(f::Function, args::Tuple{…}; before_xla_optimizations::Bool, client::Nothing, serializable::Bool, kwargs::@Kwargs{…})
    @ Reactant.Compiler ~/.julia/packages/Reactant/AO3KW/src/Compiler.jl:3708
 [12] compile_xla
    @ ~/.julia/packages/Reactant/AO3KW/src/Compiler.jl:3680 [inlined]
 [13] compile(f::Function, args::Tuple{…}; kwargs::@Kwargs{…})
    @ Reactant.Compiler ~/.julia/packages/Reactant/AO3KW/src/Compiler.jl:3802
 [14] top-level scope
    @ ~/.julia/packages/Reactant/AO3KW/src/Compiler.jl:2850
Some type information was truncated. Use `show(err)` to see complete types.

```

---

<div class="post-metadata">

**Author:** ![wsmoses](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/wsmoses/32/26497_2.png) [@wsmoses](https://discourse.julialang.org/u/wsmoses)\
**Post date:** [January 26, 2026, 12:52am UTC](https://discourse.julialang.org/t/use-of-reactant-jl-on-existing-framework/135261/5 "2026-01-26T00:52:21Z")

</div>

Currently to\_rarray isn’t allowed within a compile, which is your last issue. We should fix this, file an issue on github (but also in the interim, don’t do that?)

---

<div class="post-metadata">

**Author:** ![wsmoses](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/wsmoses/32/26497_2.png) [@wsmoses](https://discourse.julialang.org/u/wsmoses)\
**Post date:** [January 26, 2026, 12:56am UTC](https://discourse.julialang.org/t/use-of-reactant-jl-on-existing-framework/135261/6 "2026-01-26T00:56:42Z")

</div>

Not tested [on a plane atm], but I assume something like this ought work?

```julia-auto
function test_fun(T, array_type)
    x = rand(T, 100)
    dx = array_type(x)
    if dx isa ConcreteRArray
       @test sum(dx) ≈ sum(x)
    else
       @test Reactant.@jit(sum(dx)) ≈ sum(x)
    end
end

test_fun(Float32, Array)
test_fun(Float32, ConcreteRArray)

```

This is fairly similar to what’s in Reactant’s test suite itself

---

<div class="post-metadata">

**Author:** ![albertomercurio](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/albertomercurio/32/27051_2.png) [@albertomercurio](https://discourse.julialang.org/u/albertomercurio)\
**Post date:** [January 26, 2026, 1:23am UTC](https://discourse.julialang.org/t/use-of-reactant-jl-on-existing-framework/135261/7 "2026-01-26T01:23:00Z")

</div>

> [@albertomercurio](#):
>
> ConcreteRArray

Oh yes this should work. However this implies that I have to import Reactant.jl in the main tests. Now it is structured that every backend has its own environment, CUDA, Metal, Reactant and so on, with `test_fun` as shared function. Your example implies that I need to have Reactant always loaded.

---

<div class="post-metadata">

**Author:** ![wsmoses](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/wsmoses/32/26497_2.png) [@wsmoses](https://discourse.julialang.org/u/wsmoses)\
**Post date:** [January 26, 2026, 1:48am UTC](https://discourse.julialang.org/t/use-of-reactant-jl-on-existing-framework/135261/8 "2026-01-26T01:48:23Z")

</div>

I mean there’s other ways to structure this if you don’t want to import things. For example, you could also pass in an execute function, like

```julia-auto
function test_fun(T, array_type, execute)
    x = rand(T, 100)
    dx = array_type(x)
    @test execute(sum, dx) ≈ sum(x)
end

function default_exec(f, args...)
   f(args...)
end

function reactant_exec(f, args...)
   @jit f(args...)
end

```

---

<div class="post-metadata">

**Author:** ![albertomercurio](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/albertomercurio/32/27051_2.png) [@albertomercurio](https://discourse.julialang.org/u/albertomercurio)\
**Post date:** [January 26, 2026, 8:33am UTC](https://discourse.julialang.org/t/use-of-reactant-jl-on-existing-framework/135261/9 "2026-01-26T08:33:19Z")

</div>

Ok this seems the best way thanks.

I’m wondering if Reactant.jl is planning to autocompile the functions in the future, in order to avoid this extra step for all the functions.

---

<div class="post-metadata">

**Author:** ![wsmoses](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/wsmoses/32/26497_2.png) [@wsmoses](https://discourse.julialang.org/u/wsmoses)\
**Post date:** [January 26, 2026, 4:09pm UTC](https://discourse.julialang.org/t/use-of-reactant-jl-on-existing-framework/135261/10 "2026-01-26T16:09:17Z")

</div>

That is an eventual goal, but unlikely to start anytime soon.