SciRuby/nmatrix

/////////////////////////////////////////////////////////////////////
// = NMatrix
//
// A linear algebra library for scientific computation in Ruby.
// NMatrix is part of SciRuby.
//
// NMatrix was originally inspired by and derived from NArray, by
// Masahiro Tanaka: http://narray.rubyforge.org
//
// == Copyright Information
//
// SciRuby is Copyright (c) 2010 - 2014, Ruby Science Foundation
// NMatrix is Copyright (c) 2012 - 2014, John Woods and the Ruby Science Foundation
//
// Please see LICENSE.txt for additional copyright notices.
//
// == Contributing
//
// By contributing source code to SciRuby, you agree to be bound by
// our Contributor Agreement:
//
// * https://github.com/SciRuby/sciruby/wiki/Contributor-Agreement
//
// == rotg.h
//
// BLAS rotg function in native C++.
//

/*
 *             Automatically Tuned Linear Algebra Software v3.8.4
 *                    (C) Copyright 1999 R. Clint Whaley
 *
 * 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. The name of the ATLAS group or the names of its contributers may
 *      not be used to endorse or promote products derived from this
 *      software without specific 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 ATLAS GROUP OR ITS 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.
 *
 */

#ifndef ROTG_H
# define ROTG_H

namespace nm { namespace math {

/* Givens plane rotation. From ATLAS 3.8.4. */
// FIXME: Not working properly for Ruby objects.
template <typename DType>
inline void rotg(DType* a, DType* b, DType* c, DType* s) {
  DType aa    = std::abs(*a), ab = std::abs(*b);
  DType roe   = aa > ab ? *a : *b;
  DType scal  = aa + ab;

  if (scal == 0) {
    *c =  1;
    *s = *a = *b = 0;
  } else {
    DType t0  = aa / scal, t1 = ab / scal;
    DType r   = scal * std::sqrt(t0 * t0 + t1 * t1);
    if (roe < 0) r = -r;
    *c = *a / r;
    *s = *b / r;
    DType z   = (*c != 0) ? (1 / *c) : DType(1);
    *a = r;
    *b = z;
  }
}

template <>
inline void rotg(Complex64* a, Complex64* b, Complex64* c, Complex64* s) {
  rb_raise(rb_eNotImpError, "BLAS not available, and existing template requires modification for complex");
}

template <>
inline void rotg(Complex128* a, Complex128* b, Complex128* c, Complex128* s) {
  rb_raise(rb_eNotImpError, "BLAS not available, and existing template requires modification for complex");
}


template <typename DType>
inline void cblas_rotg(void* a, void* b, void* c, void* s) {
  rotg<DType>(reinterpret_cast<DType*>(a), reinterpret_cast<DType*>(b), reinterpret_cast<DType*>(c), reinterpret_cast<DType*>(s));
}


} } //nm::math

#endif // ROTG_H