eigen/blas/level1_impl.h

// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2009-2010 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#include "common.h"

int EIGEN_BLAS_FUNC(axpy)(const int *n, const RealScalar *palpha, const RealScalar *px, const int *incx, RealScalar *py,
                          const int *incy) {
  const Scalar *x = reinterpret_cast<const Scalar *>(px);
  Scalar *y = reinterpret_cast<Scalar *>(py);
  Scalar alpha = *reinterpret_cast<const Scalar *>(palpha);

  if (*n <= 0) return 0;

  if (*incx == 1 && *incy == 1)
    make_vector(y, *n) += alpha * make_vector(x, *n);
  else if (*incx > 0 && *incy > 0)
    make_vector(y, *n, *incy) += alpha * make_vector(x, *n, *incx);
  else if (*incx > 0 && *incy < 0)
    make_vector(y, *n, -*incy).reverse() += alpha * make_vector(x, *n, *incx);
  else if (*incx < 0 && *incy > 0)
    make_vector(y, *n, *incy) += alpha * make_vector(x, *n, -*incx).reverse();
  else if (*incx < 0 && *incy < 0)
    make_vector(y, *n, -*incy).reverse() += alpha * make_vector(x, *n, -*incx).reverse();

  return 0;
}

int EIGEN_BLAS_FUNC(copy)(int *n, RealScalar *px, int *incx, RealScalar *py, int *incy) {
  if (*n <= 0) return 0;

  Scalar *x = reinterpret_cast<Scalar *>(px);
  Scalar *y = reinterpret_cast<Scalar *>(py);

  // be careful, *incx==0 is allowed !!
  if (*incx == 1 && *incy == 1)
    make_vector(y, *n) = make_vector(x, *n);
  else {
    if (*incx < 0) x = x - (*n - 1) * (*incx);
    if (*incy < 0) y = y - (*n - 1) * (*incy);
    for (int i = 0; i < *n; ++i) {
      *y = *x;
      x += *incx;
      y += *incy;
    }
  }

  return 0;
}

int EIGEN_BLAS_FUNC(rotg)(RealScalar *pa, RealScalar *pb, RealScalar *pc, RealScalar *ps) {
  using std::abs;
  using std::sqrt;

  Scalar &a = *reinterpret_cast<Scalar *>(pa);
  Scalar &b = *reinterpret_cast<Scalar *>(pb);
  RealScalar *c = pc;
  Scalar *s = reinterpret_cast<Scalar *>(ps);

#if !ISCOMPLEX
  Scalar r, z;
  Scalar aa = abs(a);
  Scalar ab = abs(b);
  if ((aa + ab) == Scalar(0)) {
    *c = 1;
    *s = 0;
    r = 0;
    z = 0;
  } else {
    r = sqrt(a * a + b * b);
    Scalar amax = aa > ab ? a : b;
    r = amax > 0 ? r : -r;
    *c = a / r;
    *s = b / r;
    z = 1;
    if (aa > ab) z = *s;
    if (ab > aa && *c != RealScalar(0)) z = Scalar(1) / *c;
  }
  *pa = r;
  *pb = z;
#else
  Scalar alpha;
  RealScalar norm, scale;
  if (abs(a) == RealScalar(0)) {
    *c = RealScalar(0);
    *s = Scalar(1);
    a = b;
  } else {
    scale = abs(a) + abs(b);
    norm = scale * sqrt((numext::abs2(a / scale)) + (numext::abs2(b / scale)));
    alpha = a / abs(a);
    *c = abs(a) / norm;
    *s = alpha * numext::conj(b) / norm;
    a = alpha * norm;
  }
#endif

  //   JacobiRotation<Scalar> r;
  //   r.makeGivens(a,b);
  //   *c = r.c();
  //   *s = r.s();

  return 0;
}

int EIGEN_BLAS_FUNC(scal)(int *n, RealScalar *palpha, RealScalar *px, int *incx) {
  if (*n <= 0) return 0;

  Scalar *x = reinterpret_cast<Scalar *>(px);
  Scalar alpha = *reinterpret_cast<Scalar *>(palpha);

  if (*incx == 1)
    make_vector(x, *n) *= alpha;
  else
    make_vector(x, *n, std::abs(*incx)) *= alpha;

  return 0;
}

int EIGEN_BLAS_FUNC(swap)(int *n, RealScalar *px, int *incx, RealScalar *py, int *incy) {
  if (*n <= 0) return 0;

  Scalar *x = reinterpret_cast<Scalar *>(px);
  Scalar *y = reinterpret_cast<Scalar *>(py);

  if (*incx == 1 && *incy == 1)
    make_vector(y, *n).swap(make_vector(x, *n));
  else if (*incx > 0 && *incy > 0)
    make_vector(y, *n, *incy).swap(make_vector(x, *n, *incx));
  else if (*incx > 0 && *incy < 0)
    make_vector(y, *n, -*incy).reverse().swap(make_vector(x, *n, *incx));
  else if (*incx < 0 && *incy > 0)
    make_vector(y, *n, *incy).swap(make_vector(x, *n, -*incx).reverse());
  else if (*incx < 0 && *incy < 0)
    make_vector(y, *n, -*incy).reverse().swap(make_vector(x, *n, -*incx).reverse());

  return 1;
}