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Diffstat (limited to 'third_party/rust/half/src/lib.rs')
| -rw-r--r-- | third_party/rust/half/src/lib.rs | 217 |
1 files changed, 217 insertions, 0 deletions
diff --git a/third_party/rust/half/src/lib.rs b/third_party/rust/half/src/lib.rs new file mode 100644 index 0000000000..2c5568b035 --- /dev/null +++ b/third_party/rust/half/src/lib.rs @@ -0,0 +1,217 @@ +//! A crate that provides support for half-precision 16-bit floating point types. +//! +//! This crate provides the [`f16`] type, which is an implementation of the IEEE 754-2008 standard +//! [`binary16`] a.k.a `half` floating point type. This 16-bit floating point type is intended for +//! efficient storage where the full range and precision of a larger floating point value is not +//! required. This is especially useful for image storage formats. +//! +//! This crate also provides a [`bf16`] type, an alternative 16-bit floating point format. The +//! [`bfloat16`] format is a truncated IEEE 754 standard `binary32` float that preserves the +//! exponent to allow the same range as [`f32`] but with only 8 bits of precision (instead of 11 +//! bits for [`f16`]). See the [`bf16`] type for details. +//! +//! Because [`f16`] and [`bf16`] are primarily for efficient storage, floating point operations such +//! as addition, multiplication, etc. are not implemented by hardware. While this crate does provide +//! the appropriate trait implementations for basic operations, they each convert the value to +//! [`f32`] before performing the operation and then back afterward. When performing complex +//! arithmetic, manually convert to and from [`f32`] before and after to reduce repeated conversions +//! for each operation. +//! +//! This crate also provides a [`slice`][mod@slice] module for zero-copy in-place conversions of +//! [`u16`] slices to both [`f16`] and [`bf16`], as well as efficient vectorized conversions of +//! larger buffers of floating point values to and from these half formats. +//! +//! The crate uses `#[no_std]` by default, so can be used in embedded environments without using the +//! Rust [`std`] library. A `std` feature to enable support for the standard library is available, +//! see the [Cargo Features](#cargo-features) section below. +//! +//! A [`prelude`] module is provided for easy importing of available utility traits. +//! +//! # Cargo Features +//! +//! This crate supports a number of optional cargo features. None of these features are enabled by +//! default, even `std`. +//! +//! - **`use-intrinsics`** -- Use [`core::arch`] hardware intrinsics for `f16` and `bf16` conversions +//! if available on the compiler target. This feature currently only works on nightly Rust +//! until the corresponding intrinsics are stabilized. +//! +//! When this feature is enabled and the hardware supports it, the functions and traits in the +//! [`slice`][mod@slice] module will use vectorized SIMD intructions for increased efficiency. +//! +//! By default, without this feature, conversions are done only in software, which will also be +//! the fallback if the target does not have hardware support. Note that without the `std` +//! feature enabled, no runtime CPU feature detection is used, so the hardware support is only +//! compiled if the compiler target supports the CPU feature. +//! +//! - **`alloc`** -- Enable use of the [`alloc`] crate when not using the `std` library. +//! +//! Among other functions, 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. +//! +//! - **`std`** -- Enable features that depend on the Rust [`std`] library. This also enables the +//! `alloc` feature automatically. +//! +//! Enabling the `std` feature also enables runtime CPU feature detection when the +//! `use-intrsincis` feature is also enabled. Without this feature detection, intrinsics are only +//! used when compiler target supports the target feature. +//! +//! - **`serde`** -- Adds support for the [`serde`] crate by implementing [`Serialize`] and +//! [`Deserialize`] traits for both [`f16`] and [`bf16`]. +//! +//! - **`num-traits`** -- Adds support for the [`num-traits`] crate by implementing [`ToPrimitive`], +//! [`FromPrimitive`], [`AsPrimitive`], [`Num`], [`Float`], [`FloatCore`], and [`Bounded`] traits +//! for both [`f16`] and [`bf16`]. +//! +//! - **`bytemuck`** -- Adds support for the [`bytemuck`] crate by implementing [`Zeroable`] and +//! [`Pod`] traits for both [`f16`] and [`bf16`]. +//! +//! - **`zerocopy`** -- Adds support for the [`zerocopy`] crate by implementing [`AsBytes`] and +//! [`FromBytes`] traits for both [`f16`] and [`bf16`]. +//! +//! [`alloc`]: https://doc.rust-lang.org/alloc/ +//! [`std`]: https://doc.rust-lang.org/std/ +//! [`binary16`]: https://en.wikipedia.org/wiki/Half-precision_floating-point_format +//! [`bfloat16`]: https://en.wikipedia.org/wiki/Bfloat16_floating-point_format +//! [`serde`]: https://crates.io/crates/serde +//! [`bytemuck`]: https://crates.io/crates/bytemuck +//! [`num-traits`]: https://crates.io/crates/num-traits +//! [`zerocopy`]: https://crates.io/crates/zerocopy +#![cfg_attr( + feature = "alloc", + doc = " +[`vec`]: mod@vec" +)] +#![cfg_attr( + not(feature = "alloc"), + doc = " +[`vec`]: # +[`Vec`]: https://docs.rust-lang.org/stable/alloc/vec/struct.Vec.html" +)] +#![cfg_attr( + feature = "serde", + doc = " +[`Serialize`]: serde::Serialize +[`Deserialize`]: serde::Deserialize" +)] +#![cfg_attr( + not(feature = "serde"), + doc = " +[`Serialize`]: https://docs.rs/serde/*/serde/trait.Serialize.html +[`Deserialize`]: https://docs.rs/serde/*/serde/trait.Deserialize.html" +)] +#![cfg_attr( + feature = "num-traits", + doc = " +[`ToPrimitive`]: ::num_traits::ToPrimitive +[`FromPrimitive`]: ::num_traits::FromPrimitive +[`AsPrimitive`]: ::num_traits::AsPrimitive +[`Num`]: ::num_traits::Num +[`Float`]: ::num_traits::Float +[`FloatCore`]: ::num_traits::float::FloatCore +[`Bounded`]: ::num_traits::Bounded" +)] +#![cfg_attr( + not(feature = "num-traits"), + doc = " +[`ToPrimitive`]: https://docs.rs/num-traits/*/num_traits/cast/trait.ToPrimitive.html +[`FromPrimitive`]: https://docs.rs/num-traits/*/num_traits/cast/trait.FromPrimitive.html +[`AsPrimitive`]: https://docs.rs/num-traits/*/num_traits/cast/trait.AsPrimitive.html +[`Num`]: https://docs.rs/num-traits/*/num_traits/trait.Num.html +[`Float`]: https://docs.rs/num-traits/*/num_traits/float/trait.Float.html +[`FloatCore`]: https://docs.rs/num-traits/*/num_traits/float/trait.FloatCore.html +[`Bounded`]: https://docs.rs/num-traits/*/num_traits/bounds/trait.Bounded.html" +)] +#![cfg_attr( + feature = "bytemuck", + doc = " +[`Zeroable`]: bytemuck::Zeroable +[`Pod`]: bytemuck::Pod" +)] +#![cfg_attr( + not(feature = "bytemuck"), + doc = " +[`Zeroable`]: https://docs.rs/bytemuck/*/bytemuck/trait.Zeroable.html +[`Pod`]: https://docs.rs/bytemuck/*bytemuck/trait.Pod.html" +)] +#![cfg_attr( + feature = "zerocopy", + doc = " +[`AsBytes`]: zerocopy::AsBytes +[`FromBytes`]: zerocopy::FromBytes" +)] +#![cfg_attr( + not(feature = "zerocopy"), + doc = " +[`AsBytes`]: https://docs.rs/zerocopy/*/zerocopy/trait.AsBytes.html +[`FromBytes`]: https://docs.rs/zerocopy/*/zerocopy/trait.FromBytes.html" +)] +#![warn( + missing_docs, + missing_copy_implementations, + missing_debug_implementations, + trivial_numeric_casts, + future_incompatible +)] +#![allow(clippy::verbose_bit_mask, clippy::cast_lossless)] +#![cfg_attr(not(feature = "std"), no_std)] +#![cfg_attr( + all( + feature = "use-intrinsics", + any(target_arch = "x86", target_arch = "x86_64") + ), + feature(stdsimd, f16c_target_feature) +)] +#![doc(html_root_url = "https://docs.rs/half/1.8.2")] +#![doc(test(attr(deny(warnings), allow(unused))))] +#![cfg_attr(docsrs, feature(doc_cfg))] + +#[cfg(feature = "alloc")] +extern crate alloc; + +mod bfloat; +mod binary16; +#[cfg(feature = "num-traits")] +mod num_traits; + +pub mod slice; +#[cfg(feature = "alloc")] +#[cfg_attr(docsrs, doc(cfg(feature = "alloc")))] +pub mod vec; + +pub use bfloat::bf16; +#[doc(hidden)] +#[allow(deprecated)] +pub use binary16::consts; +pub use binary16::f16; + +/// A collection of the most used items and traits in this crate for easy importing. +/// +/// # Examples +/// +/// ```rust +/// use half::prelude::*; +/// ``` +pub mod prelude { + #[doc(no_inline)] + pub use crate::{ + bf16, f16, + slice::{HalfBitsSliceExt, HalfFloatSliceExt}, + }; + + #[cfg(feature = "alloc")] + #[doc(no_inline)] + #[cfg_attr(docsrs, doc(cfg(feature = "alloc")))] + pub use crate::vec::{HalfBitsVecExt, HalfFloatVecExt}; +} + +// Keep this module private to crate +mod private { + use crate::{bf16, f16}; + + pub trait SealedHalf {} + + impl SealedHalf for f16 {} + impl SealedHalf for bf16 {} +} |