70 lines
3 KiB
Markdown
70 lines
3 KiB
Markdown
|
# The Rust standard library's portable SIMD API
|
||
|
|
[](https://travis-ci.com/rust-lang/portable-simd)
|
||
|
|
|
||
|
|
Code repository for the [Portable SIMD Project Group](https://github.com/rust-lang/project-portable-simd).
|
||
|
|
Please refer to [CONTRIBUTING.md](./CONTRIBUTING.md) for our contributing guidelines.
|
||
|
|
|
||
|
|
The docs for this crate are published from the main branch.
|
||
|
|
You can [read them here][docs].
|
||
|
|
|
||
|
|
If you have questions about SIMD, we have begun writing a [guide][simd-guide].
|
||
|
|
We can also be found on [Zulip][zulip-project-portable-simd].
|
||
|
|
|
||
|
|
If you are interested in support for a specific architecture, you may want [stdarch] instead.
|
||
|
|
|
||
|
|
## Hello World
|
||
|
|
|
||
|
|
Now we're gonna dip our toes into this world with a small SIMD "Hello, World!" example. Make sure your compiler is up to date and using `nightly`. We can do that by running
|
||
|
|
|
||
|
|
```bash
|
||
|
|
rustup update -- nightly
|
||
|
|
```
|
||
|
|
|
||
|
|
or by setting up `rustup default nightly` or else with `cargo +nightly {build,test,run}`. After updating, run
|
||
|
|
```bash
|
||
|
|
cargo new hellosimd
|
||
|
|
```
|
||
|
|
to create a new crate. Edit `hellosimd/Cargo.toml` to be
|
||
|
|
```toml
|
||
|
|
[package]
|
||
|
|
name = "hellosimd"
|
||
|
|
version = "0.1.0"
|
||
|
|
edition = "2018"
|
||
|
|
[dependencies]
|
||
|
|
core_simd = { git = "https://github.com/rust-lang/portable-simd" }
|
||
|
|
```
|
||
|
|
|
||
|
|
and finally write this in `src/main.rs`:
|
||
|
|
```rust
|
||
|
|
use core_simd::*;
|
||
|
|
fn main() {
|
||
|
|
let a = f32x4::splat(10.0);
|
||
|
|
let b = f32x4::from_array([1.0, 2.0, 3.0, 4.0]);
|
||
|
|
println!("{:?}", a + b);
|
||
|
|
}
|
||
|
|
```
|
||
|
|
|
||
|
|
Explanation: We import all the bindings from the crate with the first line. Then, we construct our SIMD vectors with methods like `splat` or `from_array`. Finally, we can use operators on them like `+` and the appropriate SIMD instructions will be carried out. When we run `cargo run` you should get `[11.0, 12.0, 13.0, 14.0]`.
|
||
|
|
|
||
|
|
## Code Organization
|
||
|
|
|
||
|
|
Currently the crate is organized so that each element type is a file, and then the 64-bit, 128-bit, 256-bit, and 512-bit vectors using those types are contained in said file.
|
||
|
|
|
||
|
|
All types are then exported as a single, flat module.
|
||
|
|
|
||
|
|
Depending on the size of the primitive type, the number of lanes the vector will have varies. For example, 128-bit vectors have four `f32` lanes and two `f64` lanes.
|
||
|
|
|
||
|
|
The supported element types are as follows:
|
||
|
|
* **Floating Point:** `f32`, `f64`
|
||
|
|
* **Signed Integers:** `i8`, `i16`, `i32`, `i64`, `i128`, `isize`
|
||
|
|
* **Unsigned Integers:** `u8`, `u16`, `u32`, `u64`, `u128`, `usize`
|
||
|
|
* **Masks:** `mask8`, `mask16`, `mask32`, `mask64`, `mask128`, `masksize`
|
||
|
|
|
||
|
|
Floating point, signed integers, and unsigned integers are the [primitive types](https://doc.rust-lang.org/core/primitive/index.html) you're already used to.
|
||
|
|
The `mask` types are "truthy" values, but they use the number of bits in their name instead of just 1 bit like a normal `bool` uses.
|
||
|
|
|
||
|
|
[simd-guide]: ./beginners-guide.md
|
||
|
|
[zulip-project-portable-simd]: https://rust-lang.zulipchat.com/#narrow/stream/257879-project-portable-simd
|
||
|
|
[stdarch]: https://github.com/rust-lang/stdarch
|
||
|
|
[docs]: https://rust-lang.github.io/portable-simd/core_simd
|