/* -*- c++ -*- */
/*
 * Copyright 2014 Free Software Foundation, Inc.
 *
 * This file is part of GNU Radio
 *
 * GNU Radio is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3, or (at your option)
 * any later version.
 *
 * GNU Radio is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with GNU Radio; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

/*!
 * \page volk_32f_atan_32f
 *
 * \b Overview
 *
 * Computes arcsine of input vector and stores results in output vector.
 *
 * <b>Dispatcher Prototype</b>
 * \code
 * void volk_32f_atan_32f(float* bVector, const float* aVector, unsigned int num_points)
 * \endcode
 *
 * \b Inputs
 * \li aVector: The input vector of floats.
 * \li num_points: The number of data points.
 *
 * \b Outputs
 * \li bVector: The vector where results will be stored.
 *
 * \b Example
 * Calculate common angles around the top half of the unit circle.
 * \code
 *   int N = 10;
 *   unsigned int alignment = volk_get_alignment();
 *   float* in = (float*)volk_malloc(sizeof(float)*N, alignment);
 *   float* out = (float*)volk_malloc(sizeof(float)*N, alignment);
 *
 *   in[0] = 0.f;
 *   in[1] = 1.f/std::sqrt(3.f);
 *   in[2] = 1.f;
 *   in[3] = std::sqrt(3.f);
 *   in[4] = in[5] = 1e99;
 *   for(unsigned int ii = 6; ii < N; ++ii){
 *       in[ii] = - in[N-ii-1];
 *   }
 *
 *   volk_32f_atan_32f(out, in, N);
 *
 *   for(unsigned int ii = 0; ii < N; ++ii){
 *       printf("atan(%1.3f) = %1.3f\n", in[ii], out[ii]);
 *   }
 *
 *   volk_free(in);
 *   volk_free(out);
 * \endcode
 */

#include <stdio.h>
#include <math.h>
#include <inttypes.h>

/* This is the number of terms of Taylor series to evaluate, increase this for more accuracy*/
#define TERMS 2

#ifndef INCLUDED_volk_32f_atan_32f_a_H
#define INCLUDED_volk_32f_atan_32f_a_H

#ifdef LV_HAVE_SSE4_1
#include <smmintrin.h>

static inline void
volk_32f_atan_32f_a_sse4_1(float* bVector, const float* aVector, unsigned int num_points)
{
  float* bPtr = bVector;
  const float* aPtr = aVector;

  unsigned int number = 0;
  unsigned int quarterPoints = num_points / 4;
  int i, j;

  __m128 aVal, pio2, x, y, z, arctangent;
  __m128 fzeroes, fones, ftwos, ffours, condition;

  pio2 = _mm_set1_ps(3.14159265358979323846/2);
  fzeroes = _mm_setzero_ps();
  fones = _mm_set1_ps(1.0);
  ftwos = _mm_set1_ps(2.0);
  ffours = _mm_set1_ps(4.0);

  for(;number < quarterPoints; number++){
    aVal = _mm_load_ps(aPtr);
    z = aVal;
    condition = _mm_cmplt_ps(z, fzeroes);
    z = _mm_sub_ps(z, _mm_and_ps(_mm_mul_ps(z, ftwos), condition));
    x = z;
    condition = _mm_cmplt_ps(z, fones);
    x = _mm_add_ps(x, _mm_and_ps(_mm_sub_ps(_mm_div_ps(fones, z), z), condition));

    for(i = 0; i < 2; i++){
      x = _mm_add_ps(x, _mm_sqrt_ps(_mm_add_ps(fones, _mm_mul_ps(x, x))));
    }
    x = _mm_div_ps(fones, x);
    y = fzeroes;
    for(j = TERMS - 1; j >=0 ; j--){
      y = _mm_add_ps(_mm_mul_ps(y, _mm_mul_ps(x, x)), _mm_set1_ps(pow(-1,j)/(2*j+1)));
    }

    y = _mm_mul_ps(y, _mm_mul_ps(x, ffours));
    condition = _mm_cmpgt_ps(z, fones);

    y = _mm_add_ps(y, _mm_and_ps(_mm_sub_ps(pio2, _mm_mul_ps(y, ftwos)), condition));
    arctangent = y;
    condition = _mm_cmplt_ps(aVal, fzeroes);
    arctangent = _mm_sub_ps(arctangent, _mm_and_ps(_mm_mul_ps(arctangent, ftwos), condition));

    _mm_store_ps(bPtr, arctangent);
    aPtr += 4;
    bPtr += 4;
  }

  number = quarterPoints * 4;
  for(;number < num_points; number++){
    *bPtr++ = atanf(*aPtr++);
  }
}

#endif /* LV_HAVE_SSE4_1 for aligned */

#endif /* INCLUDED_volk_32f_atan_32f_a_H */

#ifndef INCLUDED_volk_32f_atan_32f_u_H
#define INCLUDED_volk_32f_atan_32f_u_H

#ifdef LV_HAVE_SSE4_1
#include <smmintrin.h>

static inline void
volk_32f_atan_32f_u_sse4_1(float* bVector, const float* aVector, unsigned int num_points)
{
  float* bPtr = bVector;
  const float* aPtr = aVector;

  unsigned int number = 0;
  unsigned int quarterPoints = num_points / 4;
  int i, j;

  __m128 aVal, pio2, x, y, z, arctangent;
  __m128 fzeroes, fones, ftwos, ffours, condition;

  pio2 = _mm_set1_ps(3.14159265358979323846/2);
  fzeroes = _mm_setzero_ps();
  fones = _mm_set1_ps(1.0);
  ftwos = _mm_set1_ps(2.0);
  ffours = _mm_set1_ps(4.0);

  for(;number < quarterPoints; number++){
    aVal = _mm_loadu_ps(aPtr);
    z = aVal;
    condition = _mm_cmplt_ps(z, fzeroes);
    z = _mm_sub_ps(z, _mm_and_ps(_mm_mul_ps(z, ftwos), condition));
    x = z;
    condition = _mm_cmplt_ps(z, fones);
    x = _mm_add_ps(x, _mm_and_ps(_mm_sub_ps(_mm_div_ps(fones, z), z), condition));

    for(i = 0; i < 2; i++)
      x = _mm_add_ps(x, _mm_sqrt_ps(_mm_add_ps(fones, _mm_mul_ps(x, x))));
    x = _mm_div_ps(fones, x);
    y = fzeroes;
    for(j = TERMS - 1; j >= 0; j--)
      y = _mm_add_ps(_mm_mul_ps(y, _mm_mul_ps(x, x)), _mm_set1_ps(pow(-1,j)/(2*j+1)));

    y = _mm_mul_ps(y, _mm_mul_ps(x, ffours));
    condition = _mm_cmpgt_ps(z, fones);

    y = _mm_add_ps(y, _mm_and_ps(_mm_sub_ps(pio2, _mm_mul_ps(y, ftwos)), condition));
    arctangent = y;
    condition = _mm_cmplt_ps(aVal, fzeroes);
    arctangent = _mm_sub_ps(arctangent, _mm_and_ps(_mm_mul_ps(arctangent, ftwos), condition));

    _mm_storeu_ps(bPtr, arctangent);
    aPtr += 4;
    bPtr += 4;
  }

  number = quarterPoints * 4;
  for(;number < num_points; number++){
    *bPtr++ = atanf(*aPtr++);
  }
}

#endif /* LV_HAVE_SSE4_1 for unaligned */

#ifdef LV_HAVE_GENERIC

static inline void
volk_32f_atan_32f_generic(float* bVector, const float* aVector, unsigned int num_points)
{
  float* bPtr = bVector;
  const float* aPtr = aVector;
  unsigned int number = 0;

  for(number = 0; number < num_points; number++){
    *bPtr++ = atanf(*aPtr++);
  }
}
#endif /* LV_HAVE_GENERIC */

#endif /* INCLUDED_volk_32f_atan_32f_u_H */
