Cargo Features

index_permute has no features set by default.

[dependencies]
index_permute = { version = "0.1.12", features = ["parallel"] }
parallel = num_cpus

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features. These features may have been created by mistake, and this functionality may be removed in the future.

num_cpus parallel?