pub trait StdFloat: Sealed + Sized {
fn fract(self) -> Self;
fn mul_add(self, a: Self, b: Self) -> Self { ... }
fn sqrt(self) -> Self { ... }
fn ceil(self) -> Self { ... }
fn floor(self) -> Self { ... }
fn round(self) -> Self { ... }
fn trunc(self) -> Self { ... }
}Expand description
This trait provides a possibly-temporary implementation of float functions
that may, in the absence of hardware support, canonicalize to calling an
operating system’s math.h dynamically-loaded library (also known as a
shared object). As these conditionally require runtime support, they
should only appear in binaries built assuming OS support: std.
However, there is no reason SIMD types, in general, need OS support,
as for many architectures an embedded binary may simply configure that
support itself. This means these types must be visible in core
but have these functions available in std.
f32 and f64 achieve a similar trick by using “lang items”, but
due to compiler limitations, it is harder to implement this approach for
abstract data types like Simd. From that need, this trait is born.
It is possible this trait will be replaced in some manner in the future,
when either the compiler or its supporting runtime functions are improved.
For now this trait is available to permit experimentation with SIMD float
operations that may lack hardware support, such as mul_add.
Required methods
Provided methods
Fused multiply-add. Computes (self * a) + b with only one rounding error,
yielding a more accurate result than an unfused multiply-add.
Using mul_add may be more performant than an unfused multiply-add if the target
architecture has a dedicated fma CPU instruction. However, this is not always
true, and will be heavily dependent on designing algorithms with specific target
hardware in mind.
Produces a vector where every lane has the square root value
of the equivalently-indexed lane in self
Returns the smallest integer greater than or equal to each lane.
Returns the largest integer value less than or equal to each lane.
Rounds to the nearest integer value. Ties round toward zero.