ankafilters/src/kernels/ankacomplex.cl

/*
 * Copyright (C) 2011-2014 Karlsruhe Institute of Technology
 *
 * This file is part of Ufo.
 *
 * This library is free software: you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation, either
 * version 3 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
 */

/**
  * multiply_frequencies_with_real_sym:
  * @frequencies: complex Fourier transform frequencies with interleaved
  * real/imaginary values
  * @output: multiplication result
  * @coefficients: first half of symmetric coefficients for the multiplication
  * (size = width / 2 + 1)
  *
  * Multiply every row of @frequencies with @coefficients which are half the *real*
  * width + 1, i.e. width = global size / 2 because of the complex numbers. This
  * kernel takes advantage of symmetry and expects @frequencies to be ordered as
  * [0, 1, ..., width / 2 - 1, -width / 2, ..., -1]. After width / 2 the @coefficients
  * are mirrored.
  */
kernel void
multiply_frequencies_with_real_sym (global float *frequencies,
                                    global float *output,
                                    constant float *coefficients)
{
    const int idx = get_global_id(0);
    const int idy = get_global_id(1);
    const int real_width = get_global_size (0) / 2;
    const int index = idy * 2 * real_width + idx;
    const int real_index = idx < real_width ? idx / 2 : real_width - idx / 2;

    output[index] = frequencies[index] * coefficients[real_index];
}