text: /*
   *  Copyright 2008-2013 NVIDIA Corporation
   *  Copyright 2013 Filipe RNC Maia
   *
   *  Licensed under the Apache License, Version 2.0 (the "License");
   *  you may not use this file except in compliance with the License.
   *  You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   *  Unless required by applicable law or agreed to in writing, software
   *  distributed under the License is distributed on an "AS IS" BASIS,
   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   *  See the License for the specific language governing permissions and
   *  limitations under the License.
   */
  
  /*-
   * Copyright (c) 2011 David Schultz <das@FreeBSD.ORG>
   * 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.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
   */
  
  /* adapted from FreeBSD:
   *    lib/msun/src/s_cexpf.c
   *    lib/msun/src/k_exp.c
   *
   */
  
  #pragma once
  
  #include <cusp/detail/thrust/complex.h>
  #include <cusp/detail/thrust/detail/complex/math_private.h>
  
  namespace thrust {
  namespace detail {
  namespace complex {
  
  __host__ __device__ inline
  float frexp_expf(float x, int *expt) {
      const uint32_t k = 235;                 /* constant for reduction */
      const float kln2 =  162.88958740F;       /* k * ln2 */
  
      // should this be a double instead?
      float exp_x;
      uint32_t hx;
  
      exp_x = expf(x - kln2);
      get_float_word(hx, exp_x);
      *expt = (hx >> 23) - (0x7f + 127) + k;
      set_float_word(exp_x, (hx & 0x7fffff) | ((0x7f + 127) << 23));
      return (exp_x);
  }
  
  __host__ __device__ inline
  complex<float>
  ldexp_cexpf(complex<float> z, int expt)
  {
      float x, y, exp_x, scale1, scale2;
      int ex_expt, half_expt;
  
      x = z.real();
      y = z.imag();
      exp_x = frexp_expf(x, &ex_expt);
      expt += ex_expt;
  
      half_expt = expt / 2;
      set_float_word(scale1, (0x7f + half_expt) << 23);
      half_expt = expt - half_expt;
      set_float_word(scale2, (0x7f + half_expt) << 23);
  
      return (complex<float>(std::cos(y) * exp_x * scale1 * scale2,
                             std::sin(y) * exp_x * scale1 * scale2));
  }
  
  __host__ __device__ inline
  complex<float> cexpf(const complex<float>& z) {
      float x, y, exp_x;
      uint32_t hx, hy;
  
      const uint32_t
      exp_ovfl  = 0x42b17218,		/* MAX_EXP * ln2 ~= 88.722839355 */
      cexp_ovfl = 0x43400074;		/* (MAX_EXP - MIN_DENORM_EXP) * ln2 */
  
      x = z.real();
      y = z.imag();
  
      get_float_word(hy, y);
      hy &= 0x7fffffff;
  
      /* cexp(x + I 0) = exp(x) + I 0 */
      if (hy == 0)
          return (complex<float>(std::exp(x), y));
      get_float_word(hx, x);
      /* cexp(0 + I y) = cos(y) + I sin(y) */
      if ((hx & 0x7fffffff) == 0) {
          return (complex<float>(std::cos(y), std::sin(y)));
      }
      if (hy >= 0x7f800000) {
          if ((hx & 0x7fffffff) != 0x7f800000) {
              /* cexp(finite|NaN +- I Inf|NaN) = NaN + I NaN */
              return (complex<float>(y - y, y - y));
          } else if (hx & 0x80000000) {
              /* cexp(-Inf +- I Inf|NaN) = 0 + I 0 */
              return (complex<float>(0.0, 0.0));
          } else {
              /* cexp(+Inf +- I Inf|NaN) = Inf + I NaN */
              return (complex<float>(x, y - y));
          }
      }
  
      if (hx >= exp_ovfl && hx <= cexp_ovfl) {
          /*
           * x is between 88.7 and 192, so we must scale to avoid
           * overflow in expf(x).
           */
          return (ldexp_cexpf(z, 0));
      } else {
          /*
           * Cases covered here:
           *  -  x < exp_ovfl and exp(x) won't overflow (common case)
           *  -  x > cexp_ovfl, so exp(x) * s overflows for all s > 0
           *  -  x = +-Inf (generated by exp())
           *  -  x = NaN (spurious inexact exception from y)
           */
          exp_x = std::exp(x);
          return (complex<float>(exp_x * std::cos(y), exp_x * std::sin(y)));
      }
  }
  
  } // namespace complex
  
  } // namespace detail
  
  template <>
  __host__ __device__
  inline complex<float> exp(const complex<float>& z) {
      return detail::complex::cexpf(z);
  }
  
  } // namespace thrust
  