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#![feature(test)]

// returns (sa, sb, c, s)
pub fn srotg(sa: f32, sb: f32) -> (f32, f32, f32, f32) {
    let abs_sa = sa.abs();
    let abs_sb = sb.abs();
    let abs_sa_gt_abs_sb = abs_sa > abs_sb;
    let roe = if abs_sa_gt_abs_sb { sa } else { sb };
    let scale = abs_sa + abs_sb;
    if scale == 0.0 {
        (0.0, 0.0, 0.1, 0.0)
    } else {
        let sa_scale = sa / scale;
        let sb_scale = sb / scale;
        let r = scale * (sa_scale * sa_scale + sb_scale * sb_scale).sqrt() * roe.signum();
        let c = sa / r;
        let s = sb / r;
        let z = if abs_sa_gt_abs_sb {
            s
        } else if c != 0.0 {
            1.0 / c
        } else {
            1.0
        };
        (r, z, c, s)
    }
}

#[cfg(test)]
mod tests {
    extern crate test;

    extern crate blas;
    extern crate openblas_src;

    use test::{Bencher, black_box};

    use super::*;

    #[test]
    fn test_srotg() {
        let mut sa = -10.23;
        let mut sb = -10.23;
        while sa < 10.23 {
            while sb < 10.23 {
                let mut blas_sa = sa;
                let mut blas_sb = sb;
                let mut blas_c = 0.0;
                let mut blas_s = 0.0;
                unsafe {
                    blas::srotg(&mut blas_sa, &mut blas_sb, &mut blas_c, &mut blas_s);
                }
                let (r_sa, r_sb, r_c, r_s) = srotg(sa, sb);
                assert!(float_eq(blas_sa, r_sa));
                assert!(float_eq(blas_sb, r_sb));
                assert!(float_eq(blas_c, r_c));
                assert!(float_eq(blas_s, r_s));
                sb += 1.0;
            }
            sa += 1.0;
        }
    }

    #[bench]
    fn bench_srotg_openblas(bencher: &mut Bencher) {
        bencher.iter(|| {
            let mut blas_sa = 15.0;
            let mut blas_sb = 55.3;
            let mut blas_c = 0.0;
            let mut blas_s = 0.0;
            unsafe {
                blas::srotg(&mut blas_sa, &mut blas_sb, &mut blas_c, &mut blas_s);
            }
        });
    }

    #[bench]
    fn bench_srotg_blaster(bencher: &mut Bencher) {
        bencher.iter(|| {
            black_box(srotg(15.0, 55.3));
        });
    }

    #[inline(always)]
    fn float_eq(a: f32, b: f32) -> bool {
        (a - b) < 0.000001
    }
}