softposit-rs

Rust port of SoftPosit repository.

Such types are supported now:

• P32E2 or P32: 32-bit posit with exponent size ES=2;
• P16E1 or P16: 16-bit posit with ES=1;
• P8E0 or P8: 8-bit posit without exponent bits.

Initial support of generic types PxE1{N} and PxE2{N}. Requires rust 1.51.

Examples

Convert from f64, Add

use softposit::P32;

fn main() {
    let a = P32::from(12.3);
    let b = P32::from(154.);
    let c = a + b;
    println!("c = {0} or c = {0:?}", c);
}

Quire

Each Posit type has correspondent Quire type (Q32, Q16, Q8). These types support AddAssign and SubAssign operations. For example:

use softposit::{P32, Q32};

// c == 12.3*0.4 - 6.3*8.4 == -48;
fn main() {
    let mut q = Q32::init();
    q += (P32::from(12.3), P32::from(0.4));
    q -= (P32::from(6.3), P32::from(8.4));
    let c = q.to_posit();
    println!("c = {0} or c = {0:?}", c);
}

Math

Math functions, like trigonomentic, are partially implemented for P32E2 type. For complex computations use num::Complex type.

Linear algebra

You can also use matrix operations, defined in nalgebra crate by using linalg feature:

use softposit::P32;

use nalgebra::{Dynamic, Matrix, VecStorage};
type DMatrix = Matrix<P32, Dynamic, Dynamic, VecStorage<P32, Dynamic, Dynamic>>;

fn main() {
    let a = DMatrix::new_random(5, 5);
    println!("Matrix A = {}", a);
    let decomp = &a.clone().lu();
    if let Some(c) = decomp.try_inverse() {
        println!("Inverse matrix Aˉ¹ = {}", c);
        println!("Check Identity");
        let ones = a * c;
        println!("A × Aˉ¹ = {}", ones);
    } else {
        println!("Matrix A can't be inverted");
    }
}

cargo build --features="linalg,rand"

Benchmarking

cargo bench

Type	Operation	i3-2310M @ 2.10GHz	i5-3470 @ 3.20GHz
P32E2	+	47 MPOPS	82 MPOPS
	-	45 MPOPS	83 MPOPS
	*	56 MPOPS	99 MPOPS
	/	25 MPOPS	42 MPOPS
	√⎺⎺	48 MPOPS	92 MPOPS
	round	89 MPOPS	159 MPOPS