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use blas;
use lapack;

use Result;
use format::Conventional;
use operation::{Multiply, MultiplyInto, ScaleSelf, SymmetricEigen};

impl Multiply<[f64], Conventional<f64>> for Conventional<f64> {
    #[inline]
    fn multiply(&self, right: &[f64]) -> Self {
        let (m, p) = (self.rows, self.columns);
        let n = right.len() / p;
        let mut result = unsafe { Conventional::with_uninitialized((m, n)) };
        multiply(1.0, &self.values, right, 0.0, &mut result.values, m, p, n);
        result
    }
}

impl MultiplyInto<Conventional<f64>, [f64]> for Conventional<f64> {
    #[inline(always)]
    fn multiply_into(&self, right: &Self, result: &mut [f64]) {
        MultiplyInto::multiply_into(self, &*right as &[f64], result)
    }
}

impl MultiplyInto<[f64], [f64]> for Conventional<f64> {
    #[inline]
    fn multiply_into(&self, right: &[f64], result: &mut [f64]) {
        let (m, p) = (self.rows, self.columns);
        let n = right.len() / p;
        multiply(1.0, &self.values, right, 1.0, result, m, p, n)
    }
}

impl ScaleSelf<f64> for [f64] {
    #[inline]
    fn scale_self(&mut self, alpha: f64) {
        blas::dscal(self.len(), alpha, self, 1);
    }
}

impl<'l> SymmetricEigen for (&'l mut [f64], &'l mut [f64]) {
    #[inline]
    fn decompose(pair: &mut Self) -> Result<()> {
        let m = pair.1.len();
        try!(decompose(pair.0, pair.1, m));
        Ok(())
    }
}

fn multiply(alpha: f64, a: &[f64], b: &[f64], beta: f64, c: &mut [f64], m: usize, p: usize,
            n: usize) {

    debug_assert_eq!(a.len(), m * p);
    debug_assert_eq!(b.len(), p * n);
    debug_assert_eq!(c.len(), m * n);
    if n == 1 {
        blas::dgemv(b'N', m, p, alpha, a, m, b, 1, beta, c, 1);
    } else {
        blas::dgemm(b'N', b'N', m, n, p, alpha, a, m, b, p, beta, c, m);
    }
}

fn decompose(matrix: &mut [f64], vector: &mut [f64], m: usize) -> Result<()> {
    debug_assert_eq!(matrix.len(), m * m);
    debug_assert_eq!(vector.len(), m);

    macro_rules! success(
        ($flag:expr) => (
            if $flag != 0 {
                raise!("encountered invalid arguments");
            } else if $flag > 0 {
                raise!("failed to converge");
            }
        );
    );

    let mut flag = 0;

    let mut work = [0.0];
    lapack::dsyev(b'V', b'U', m, matrix, m, vector, &mut work, -1isize as usize, &mut flag);
    success!(flag);

    let size = work[0] as usize;
    let mut work = Vec::with_capacity(size);
    unsafe { work.set_len(size) };
    lapack::dsyev(b'V', b'U', m, matrix, m, vector, &mut work, size, &mut flag);
    success!(flag);

    Ok(())
}

#[cfg(test)]
mod tests {
    use assert;
    use prelude::*;

    #[test]
    fn multiply() {
        let matrix = Conventional::from_vec((2, 3), vec![
            1.0, 2.0, 3.0, 4.0, 5.0, 6.0,
        ]);
        let right = Conventional::from_vec((3, 4), vec![
            1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0,
        ]);

        assert_eq!(matrix.multiply(&right), Conventional::from_vec((2, 4), vec![
            22.0, 28.0, 49.0, 64.0, 76.0, 100.0, 103.0, 136.0,
        ]));
    }

    #[test]
    fn multiply_into() {
        let matrix = Conventional::from_vec((2, 3), vec![
            1.0, 2.0, 3.0, 4.0, 5.0, 6.0,
        ]);
        let right = Conventional::from_vec((3, 4), vec![
            1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0,
        ]);
        let mut result = Conventional::from_vec((2, 4), vec![
            1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0,
        ]);

        matrix.multiply_into(&right, &mut result);

        assert_eq!(result, Conventional::from_vec((2, 4), vec![
            23.0, 30.0, 52.0, 68.0, 81.0, 106.0, 110.0, 144.0,
        ]));
    }

    #[test]
    fn scale_self() {
        let mut matrix = Conventional::from_vec(2, vec![21.0, 21.0, 21.0, 21.0]);
        matrix.scale_self(2.0);
        assert_eq!(matrix, Conventional::from_vec(2, vec![42.0, 42.0, 42.0, 42.0]));
    }

    #[test]
    fn symmetric_eigen() {
        let mut matrix = Conventional::from_vec(5, vec![
            0.814723686393179, 0.097540404999410, 0.157613081677548, 0.141886338627215,
            0.655740699156587, 0.097540404999410, 0.278498218867048, 0.970592781760616,
            0.421761282626275, 0.035711678574190, 0.157613081677548, 0.970592781760616,
            0.957166948242946, 0.915735525189067, 0.849129305868777, 0.141886338627215,
            0.421761282626275, 0.915735525189067, 0.792207329559554, 0.933993247757551,
            0.655740699156587, 0.035711678574190, 0.849129305868777, 0.933993247757551,
            0.678735154857773,
        ]);
        let mut vector = Conventional::from_vec((1, 5), vec![0.0; 5]);

        assert!(SymmetricEigen::decompose(&mut (&mut *matrix, &mut *vector)).is_ok());

        assert::close(&*matrix, &*vec![
             0.200767588469279, -0.613521879994358,  0.529492579537623,  0.161735212201923,
            -0.526082320114459, -0.241005628008408, -0.272281143378657,  0.443280672960843,
            -0.675165120368165,  0.464148221418878,  0.509762909240926,  0.555609456752178,
             0.244072927029371, -0.492754485897426, -0.359251069377747, -0.766321363493223,
             0.386556170387878,  0.341170928524320,  0.084643789583352, -0.373849864790357,
             0.233456648876442,  0.302202482503382,  0.589211894835079,  0.517708631263932,
             0.488854547655902,
        ], 1e-14);
        assert::close(&*vector, &*vec![
            -0.671640666831794, -0.230366398529950, 0.397221322493687, 0.999582068576074,
             3.026535012212483,
        ], 1e-14);
    }
}