Missing atomic operators for `Data.Primitive.ByteArray`

[TerrorJack]

There are several atomic primops for MutableByteArray# like casIntArray#, fetchAddIntArray#, yet they don't have shims in Data.Primitive.ByteArray yet. Mind if I open a PR for this?

[treeowl]

Please do!

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On Mon, Apr 2, 2018, 9:15 AM Shao Cheng ***@***.***> wrote: There are several atomic primops for MutableByteArray# like casIntArray#, fetchAddIntArray#, yet they don't have shims in Data.Primitive.ByteArray yet. Mind if I open a PR for this? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#122>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABzi_SCcjse67Hc5Ksasi09s9QwpxQYwks5tkcHmgaJpZM4TDMWa> .

[cartazio]

@TerrorJack .... plase make sure they have a consistent size on both 32bit and 64bit platforms....

Theres also gonna be some gotchas (i imagine) with alignment plus how this interacts with cache line synchronization etc. so lets make sure we understand the semantics and performance characteristics before we merge it in.

[andrewthad]

make sure they have a consistent size on both 32bit and 64bit platforms

Isn't the only way to implement this to make them have inconsistent sizes on 32 bit vs 64 bit platforms? I think this has to use machine-sized words.

[cartazio]

I’ll have to double check what’s available on the various target platforms. I guess I’m just uncomfortable with a byte varying per platform operation on bytearrays. Illl need to think about this

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On Tue, Apr 3, 2018 at 3:07 PM Andrew Martin ***@***.***> wrote: make sure they have a consistent size on both 32bit and 64bit platforms Isn't the only way to implement this to make them have inconsistent sizes on 32 bit vs 64 bit platforms? I think this has to use machine-sized words. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#122 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAAQwoeTibieji1aug7OV_vK0Q_z1a87ks5tk8hsgaJpZM4TDMWa> .

[andrewthad]

It's worth considering that we are already in this situation. This bit of code

writeByteArray myArray 1 (1 :: Int)

behaves differently on a 32-bit platform and a 64-bit platform.

[andrewthad]

I have two PRs exploring different approaches to implementing these primops:

• add PrimMach typeclass and implement casPrimArray with it #152: more general
• add PrimArray wrappers for casIntArray #151: less general

Both of these only add primops to PrimArray, but these could easily be added to the ByteArray module as well.

[andrewthad]

I have written a library that implements this: primitive-atomic. I will consider merging this into primitive, although I'm not certain that it meets a terribly dire need.