aosp12/external/rust/crates/half

f16 and bf16 floating point types for Rust

This crate implements a half-precision floating point f16 type for Rust implementing the IEEE 754-2008 standard binary16 a.k.a half format, as well as a bf16 type implementing the bfloat16 format.

Usage

The f16 and bf16 types provides conversion operations as a normal Rust floating point type, but since they are primarily leveraged for minimal floating point storage and most major hardware does not implement them, all math operations should be done as an f32 type.

This crate provides no_std support by default so can easily be used in embedded code where a smaller float format is most useful.

Requires Rust 1.32 or greater. If you need support for older versions of Rust, use versions 1.3 and earlier of this crate.

See the crate documentation for more details.

Optional Features

• serde - Implement Serialize and Deserialize traits for f16 and bf16. This adds a dependency on the serde crate.

• use-intrinsics - Use hardware intrinsics for f16 and bf16 conversions if available on the compiler host target. By default, without this feature, conversions are done only in software, which will be the fallback if the host target does not have hardware support. Available only on Rust nightly channel.

• alloc - Enable use of the alloc crate when not using the std library.

  This enables the vec module, which contains zero-copy conversions for the Vec type. This allows fast conversion between raw Vec<u16> bits and Vec<f16> or Vec<bf16> arrays, and vice versa. Requires Rust 1.36 or greater.

• std - Enable features that depend on the Rust std library, including everything in the alloc feature.

  Enabling the std feature enables runtime CPU feature detection when the use-intrsincis feature is also enabled. Without this feature detection, intrinsics are only used when compiler host target supports them.

• num-traits - Enable ToPrimitive and FromPrimitive trait implementations from the num-traits crate.

• bytemuck - Enable Zeroable and Pod trait implementations from the bytemuck crate.

More Documentation

• Crate API Reference
• Latest Changes

License

This library is distributed under the terms of either of:

• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)

at your option.

Contributing

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.