ladiv.tcc (flens/lapack/la/ladiv.tcc)

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/*
*   Copyright (c) 2011, Michael Lehn
*
*   All rights reserved.
*
*   Redistribution and use in source and binary forms, with or without
*   modification, are permitted provided that the following conditions
*   are met:
*
*   1) Redistributions of source code must retain the above copyright
*      notice, this list of conditions and the following disclaimer.
*   2) Redistributions in binary form must reproduce the above copyright
*      notice, this list of conditions and the following disclaimer in
*      the documentation and/or other materials provided with the
*      distribution.
*   3) Neither the name of the FLENS development group nor the names of
*      its contributors may be used to endorse or promote products derived
*      from this software without specific prior written permission.
*
*   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
*   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
*   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
*   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
*   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
*   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
*   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
*   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
*   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
*   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
*   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

/* Based on
*
      SUBROUTINE DLADIV( A, B, C, D, P, Q )
*
*  -- LAPACK auxiliary routine (version 3.2) --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*     November 2006
*/

#ifndef FLENS_LAPACK_LA_LADIV_TCC
#define FLENS_LAPACK_LA_LADIV_TCC 1

#include <cmath>
#include <flens/lapack/lapack.h>

namespace flens { namespace lapack {

//== generic lapack implementation =============================================
template <typename T>
void
ladiv(const T &a, const T &b, const T &c, const T &d, T &p, T &q)
{
    LAPACK_DEBUG_OUT("ladiv");

    using std::abs;

    if (abs(d)<abs(c)) {
        const T e = d / c;
        const T f = c + d*e;
        p = (a + b*e) / f;
        q = (b - a*e) / f;
    } else {
        const T e = c / d;
        const T f = d + c*e;
        p = ( b + a*e) / f;
        q = (-a + b*e) / f;
    }
}

template <typename T>
std::complex<T>
ladiv(const std::complex<T> &x, const std::complex<T> &y)
{
    std::complex<T> z;
    ladiv(x.real(), x.imag(), y.real(), y.imag(), z.real(), z.imag());
    return z;
}

} } // namespace lapack, flens

#endif // FLENS_LAPACK_LA_LADIV_TCC