Is it possible to have an AtomicReference to a lis...

# kotlin-native

[martmists]

Is it possible to have an AtomicReference to a list? I'm getting this error:

Uncaught Kotlin exception: kotlin.native.concurrent.InvalidMutabilityException: mutation attempt of frozen kotlin.collections.ArrayList@1aa3f68
    at kfun:kotlin.Throwable#<init>(kotlin.String?){} (0x4169a9)
    at kfun:kotlin.Exception#<init>(kotlin.String?){} (0x410c87)
    at kfun:kotlin.RuntimeException#<init>(kotlin.String?){} (0x410d97)
    at kfun:kotlin.native.concurrent.InvalidMutabilityException#<init>(kotlin.String){} (0x433557)
    at ThrowInvalidMutabilityException (0x434a76)
    at Kotlin_AtomicReference_checkIfFrozen (0x523c71)
    at kfun:kotlin.native.concurrent.AtomicReference#<init>(1:0){} (0x4328ae)
    at ...

[KamilH]

Depends on what you would like to achieve, but maybe you should take a look at the Stately library and its collections implementation:
https://github.com/touchlab/Stately#stately-iso-collections

[Dominaezzz]

You can have an atomic reference but you can't mutate the list itself.

[martmists]

I'm not mutating the list though, this just happens when doing AtomicReference(someList)

[martmists]

I do swap out the list for different ones but I never modify it

[martmists]

and it seems the Stately collections are too slow for real-time audio ^^'

[Dominaezzz]

Hmm, will have to see code then.

[martmists]

open class IIRNode<T>(coeffsA: List<Float>, coeffsB: List<Float>) : MonoNode<T>() {
    private val coeffsA = AtomicReference(coeffsA)
    private val coeffsB = AtomicReference(coeffsB)
    constructor(order: Int) : this(List(order+1) { 1f }, List(order+1) { 1f })

    /* ... */
}

[Dominaezzz]

That's suspicious. You don't know if those list aren't mutated after construction. You might want to take a defensive copy.

[martmists]

Unless K/N mutates them by itself I'm positive they are never modified. Even so, this errors in the AtomicReference constructor

[Dominaezzz]

Ah I see, odd. Seems youtrack worthy then.

[russhwolf]

Does it work if you freeze manually before adding to atomic ref? private val coeffsA = AtomicReference(coeffsA.freeze()) etc

[martmists]

manually freezing does not solve it, no

[russhwolf]

What does the code look like where you're constructing a IIRNode?

[martmists]

I just managed to recreate it with just val x = AtomicReference(List(10) { 1f })

[russhwolf]

val x = AtomicReference(List(10) { 1f }.freeze()) should work

[russhwolf]

If it doesn't then I have no idea

[Dominaezzz]

Does the stack trace at least look different?