Test f32 vs f64 sinf kernel

main.rs

const S1: f64 = -0.166666666416265235595; /* -0x15555554cbac77.0p-55 */
const S2: f64 = 0.0083333293858894631756; /*  0x111110896efbb2.0p-59 */
const S3: f64 = -0.000198393348360966317347; /* -0x1a00f9e2cae774.0p-65 */
const S4: f64 = 0.0000027183114939898219064; /*  0x16cd878c3b46a7.0p-71 */

pub fn k_sinf(x: f64) -> f32 {
    let z = x * x;
    let w = z * z;
    let r = S3 + z * S4;
    let s = z * x;
    ((x + s * (S1 + z * S2)) + s * w * r) as f32
}

const S1_F32: f32 = -0.166666666416265235595; /* -0x15555554cbac77.0p-55 */
const S2_F32: f32 = 0.0083333293858894631756; /*  0x111110896efbb2.0p-59 */
const S3_F32: f32 = -0.000198393348360966317347; /* -0x1a00f9e2cae774.0p-65 */
const S4_F32: f32 = 0.0000027183114939898219064; /*  0x16cd878c3b46a7.0p-71 */

fn k_sinf_f32(x: f32) -> f32 {
    let z = x * x;
    let w = z * z;
    let r = S3_F32 + z * S4_F32;
    let s = z * x;
    ((x + s * (S1_F32 + z * S2_F32)) + s * w * r)
}

use std::f32::consts::PI;

fn main() {
    let mut max_error: f32 = 0.0;

    for n in 0..100001 {
        let input = PI / 4.0 / 100000.0 * n as f32;

        let high_prec = k_sinf(input as f64);
        let low_prec = k_sinf_f32(input);

        let error = (high_prec - low_prec).abs();
        max_error = max_error.max(error);

        //println!("Error for input {} = {}", input, error);
    }

    println!("Max error = {}", max_error);
}