fn erf_impl()

in candle-core/src/cpu/erf.rs [599:710]
110 lines of code
23 McCabe index (conditional complexity)

fn erf_impl(z: f64, inv: bool) -> f64 {
    if z < 0.0 {
        if !inv {
            return -erf_impl(-z, false);
        }
        if z < -0.5 {
            return 2.0 - erf_impl(-z, true);
        }
        return 1.0 + erf_impl(-z, false);
    }

    let result = if z < 0.5 {
        if z < 1e-10 {
            z * 1.125 + z * 0.003379167095512573896158903121545171688
        } else {
            z * 1.125
                + z * evaluate::polynomial(z, ERF_IMPL_AN) / evaluate::polynomial(z, ERF_IMPL_AD)
        }
    } else if z < 110.0 {
        let (r, b) = if z < 0.75 {
            (
                evaluate::polynomial(z - 0.5, ERF_IMPL_BN)
                    / evaluate::polynomial(z - 0.5, ERF_IMPL_BD),
                0.3440242112,
            )
        } else if z < 1.25 {
            (
                evaluate::polynomial(z - 0.75, ERF_IMPL_CN)
                    / evaluate::polynomial(z - 0.75, ERF_IMPL_CD),
                0.419990927,
            )
        } else if z < 2.25 {
            (
                evaluate::polynomial(z - 1.25, ERF_IMPL_DN)
                    / evaluate::polynomial(z - 1.25, ERF_IMPL_DD),
                0.4898625016,
            )
        } else if z < 3.5 {
            (
                evaluate::polynomial(z - 2.25, ERF_IMPL_EN)
                    / evaluate::polynomial(z - 2.25, ERF_IMPL_ED),
                0.5317370892,
            )
        } else if z < 5.25 {
            (
                evaluate::polynomial(z - 3.5, ERF_IMPL_FN)
                    / evaluate::polynomial(z - 3.5, ERF_IMPL_FD),
                0.5489973426,
            )
        } else if z < 8.0 {
            (
                evaluate::polynomial(z - 5.25, ERF_IMPL_GN)
                    / evaluate::polynomial(z - 5.25, ERF_IMPL_GD),
                0.5571740866,
            )
        } else if z < 11.5 {
            (
                evaluate::polynomial(z - 8.0, ERF_IMPL_HN)
                    / evaluate::polynomial(z - 8.0, ERF_IMPL_HD),
                0.5609807968,
            )
        } else if z < 17.0 {
            (
                evaluate::polynomial(z - 11.5, ERF_IMPL_IN)
                    / evaluate::polynomial(z - 11.5, ERF_IMPL_ID),
                0.5626493692,
            )
        } else if z < 24.0 {
            (
                evaluate::polynomial(z - 17.0, ERF_IMPL_JN)
                    / evaluate::polynomial(z - 17.0, ERF_IMPL_JD),
                0.5634598136,
            )
        } else if z < 38.0 {
            (
                evaluate::polynomial(z - 24.0, ERF_IMPL_KN)
                    / evaluate::polynomial(z - 24.0, ERF_IMPL_KD),
                0.5638477802,
            )
        } else if z < 60.0 {
            (
                evaluate::polynomial(z - 38.0, ERF_IMPL_LN)
                    / evaluate::polynomial(z - 38.0, ERF_IMPL_LD),
                0.5640528202,
            )
        } else if z < 85.0 {
            (
                evaluate::polynomial(z - 60.0, ERF_IMPL_MN)
                    / evaluate::polynomial(z - 60.0, ERF_IMPL_MD),
                0.5641309023,
            )
        } else {
            (
                evaluate::polynomial(z - 85.0, ERF_IMPL_NN)
                    / evaluate::polynomial(z - 85.0, ERF_IMPL_ND),
                0.5641584396,
            )
        };
        let g = (-z * z).exp() / z;
        g * b + g * r
    } else {
        0.0
    };

    if inv && z >= 0.5 {
        result
    } else if z >= 0.5 || inv {
        1.0 - result
    } else {
        result
    }
}