Documenting building with simd feature

[andygrove]

Describe the bug

~/release/apache-arrow-datafusion-5.0.0 via 🦀 v1.54.0 
✦ ❯ cargo build --release --features "simd"
   Compiling packed_simd_2 v0.3.5
error[E0554]: `#![feature]` may not be used on the stable release channel
   --> /home/andy/.cargo/registry/src/github.aaakk.us.kg-1ecc6299db9ec823/packed_simd_2-0.3.5/src/lib.rs:214:1
    |
214 | / #![feature(
215 | |     const_generics,
216 | |     repr_simd,
217 | |     rustc_attrs,
...   |
227 | |     llvm_asm
228 | | )]
    | |__^

To Reproduce
Run command above.

[andygrove]

I am probably doing something wrong and/or we need better docs around this

[jorgecarleitao]

I think you need the nightly channel to use simd, as packed_simd requires nightly.

…

On Sat, Aug 14, 2021, 15:23 Andy Grove ***@***.***> wrote: I am probably doing something wrong and/or we need better docs around this — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#882 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAVE476BBDW7CIC4CIG3E73T4Z37PANCNFSM5CFEPPIQ> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&utm_campaign=notification-email> .

[alamb]

cargo +nightly build --release --features "simd"

[Dandandan]

I changed the issue to add some docs around this.

Btw, @andygrove AFAIK the SIMD option doesn't help a lot with the TPC-H queries. Building with snmalloc or mimalloc and fat LTO (longer build time) does improve execution times.

[houqp]

It would be good if we can provide doc on how to produce the most optimized build: simd + snmalloc + LTO.

[alamb]

I also think we should suggest building with native and/or at least avx2 instructions (by default my rustc only used sse/sse2, presumably for compatibility)

[Dandandan]

Here is an example of using all the options:

https://github.com/h2oai/db-benchmark/pull/182/files

[matthewmturner]

Hello. I could try this. To confirm - is the idea to add docs just for SIMD? Or for the most optimized build?

[houqp]

I would love to have docs for the most optimized build, but we can start with SIMD if that's too much :)