[Rust] packed_simd requires nightly

[asfimport]

See rust-lang/rfcs#2366 for more info on stabilization of this crate.

 

error[E0554]: `#![feature]` may not be used on the stable release channel
   --> /home/andy/.cargo/registry/src/github.com-1ecc6299db9ec823/packed_simd-0.3.3/src/lib.rs:202:1
    |
202 | / #![feature(
203 | |     repr_simd,
204 | |     const_fn,
205 | |     platform_intrinsics,
...   |
215 | |     custom_inner_attributes
216 | | )]
    | |__^
 

Reporter: Andy Grove / @andygrove

Related issues:

• [Rust] DivideByZero when running arrow crate when simd feature is disabled (relates to)

PRs and other links:

• GitHub Pull Request #7037

_{Note: This issue was originally created as ARROW-6718. Please see the migration documentation for further details.}

[asfimport]

Neville Dipale / @nevi-me:
If everyone's happy with the performance of arithmetic and compute kernels after the improvements to the non-SIMD functions (ARROW-7460), I'd like to propose removing packed_simd @paddyhoran

[asfimport]

Paddy Horan / @paddyhoran:
I would love to get back on stable.  I added a feature to disable explicit SIMD to try and make progress toward this goal.  Although the main thing we need is specialization on stable.

 

If we can get the same level of performance then I'm all for removing packed_simd.  At the time we adopted it, the author was trying to get it adopted into std.  Since then he has stopped driving this forward until other features land.

 

I'll take a look in the next few days to compare performance, etc. 

[asfimport]

Kyle Strand:
There is now a portable-SIMD Rust language working group: https://blog.rust-lang.org/inside-rust/2020/09/29/Portable-SIMD-PG.html

Their goal is to make "a portable SIMD API available to stable Rust users." We should follow their progress and adopt their recommendations.

[asfimport]

Andrew Lamb / @alamb:
Migrated to github: apache/arrow-rs#54