setting RUSTFLAGS for linux

[ritchie46]

Comment:

For linux we build polars with the following RUSTFLAGS as environment var:

export RUSTFLAGS='-C target-feature=+fxsr,+sse,+sse2,+sse3,+ssse3,+sse4.1,+sse4.2,+popcnt,+avx,+fma'

Where should I put these. I see a build.sh, but I think that will also be used by os-x.

Is it best to set it in the run_docker_build.sh?

[xhochy]

It needs to be in build.sh as everything outside of recipe/ is auto-generated. Still, conda-forge supports a wider userbase where not everyone has AVX capable CPUs. Thus we should be careful what we set here. conda also supports CPU (feature) detection but we haven't used this in conda-forge yet, see the following issue for that: conda-forge/conda-forge.github.io#1261

You should be able to safeguard this with the following in build.sh:

if [[ "${target_platform}" == "linux-64" ]]; then
  ...
fi

[Maxyme]

What could be an option, is to use x86_features if they are available by checking at for them at runtime (https://doc.rust-lang.org/std/macro.is_x86_feature_detected.html)
I think this could be useful for this: https://docs.rs/simdeez/0.2.4/simdeez/index.html

[ritchie46]

We don't have runtime detectable simd in polars. We could define a minimal set. This is what I have done in the polars CI as well.
The current set is the one where we did not get an issue that it was not working for them. ;)

I could drop the avx feauture (note that it is not avx512). That would already be far more than the rustc defaults.

[ritchie46]

fixed by #11