kopia lustrzana https://github.com/Dsplib/libdspl-2.0
208 wiersze
8.2 KiB
C
208 wiersze
8.2 KiB
C
/*
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* Copyright (c) 2015-2024 Sergey Bakhurin
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* Digital Signal Processing Library [http://dsplib.org]
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*
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* This file is part of libdspl-2.0.
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*
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* is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* DSPL is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with Foobar. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <float.h>
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#include "dspl.h"
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#ifdef DOXYGEN_ENGLISH
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/*! ****************************************************************************
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\ingroup DFT_GROUP
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\brief Inverse fast Fourier transform
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Function calculates \f$ n \f$-point IFFT of complex data
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\f$ x(m) \f$, \f$ m = 0 \ldots n-1 \f$. \n
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\f[
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Y(k) = \frac{1}{N} \sum_{m = 0}^{n-1} x(m) \exp
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\left( j \frac{2\pi}{n} m k \right),
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\f]
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here \f$ k = 0 \ldots n-1 \f$.
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\param[in] x
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Pointer to the input vector \f$x(m)\f$,
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\f$ m = 0 \ldots n-1 \f$. \n
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Vector size is `[n x 1]`. \n \n
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\param[in] n
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IFFT size \f$n\f$. \n
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IFFT size can be composite:
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\f$n = n_0 \times n_1 \times n_2 \times \ldots \times n_p \times m\f$,
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here \f$n_i = 2,3,5,7\f$, а \f$m \f$ --
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simple number less than 46340
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(see \ref fft_create function). \n \n
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\param[in] pfft
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Pointer to the `fft_t` object. \n
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This pointer cannot be `NULL`. \n
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Structure \ref fft_t should be previously once
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filled with the \ref fft_create function, and the memory should be
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cleared before exiting by the \ref fft_free function. \n \n
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\param[out] y
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Pointer to the IFFT result vector \f$Y(k)\f$,
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\f$ k = 0 \ldots n-1 \f$. \n
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Vector size is `[n x 1]`. \n
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Memory must be allocated. \n \n
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\return
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`RES_OK` if IFFT is calculated successfully. \n
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Else \ref ERROR_CODE_GROUP "code error".
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IFFT example:
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\include ifft_cmplx_test.c
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Result:
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\verbatim
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| x[ 0] = 1.000 0.000 | y[ 0] = -0.517 0.686 | z[ 0] = 1.000 0.000 |
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| x[ 1] = 0.540 0.841 | y[ 1] = -0.943 0.879 | z[ 1] = 0.540 0.841 |
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| x[ 2] = -0.416 0.909 | y[ 2] = -2.299 1.492 | z[ 2] = -0.416 0.909 |
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| x[ 3] = -0.990 0.141 | y[ 3] = 16.078 -6.820 | z[ 3] = -0.990 0.141 |
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| x[ 4] = -0.654 -0.757 | y[ 4] = 2.040 -0.470 | z[ 4] = -0.654 -0.757 |
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| x[ 5] = 0.284 -0.959 | y[ 5] = 1.130 -0.059 | z[ 5] = 0.284 -0.959 |
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| x[ 6] = 0.960 -0.279 | y[ 6] = 0.786 0.097 | z[ 6] = 0.960 -0.279 |
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| x[ 7] = 0.754 0.657 | y[ 7] = 0.596 0.183 | z[ 7] = 0.754 0.657 |
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| x[ 8] = -0.146 0.989 | y[ 8] = 0.470 0.240 | z[ 8] = -0.146 0.989 |
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| x[ 9] = -0.911 0.412 | y[ 9] = 0.375 0.283 | z[ 9] = -0.911 0.412 |
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| x[10] = -0.839 -0.544 | y[10] = 0.297 0.318 | z[10] = -0.839 -0.544 |
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| x[11] = 0.004 -1.000 | y[11] = 0.227 0.350 | z[11] = 0.004 -1.000 |
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| x[12] = 0.844 -0.537 | y[12] = 0.161 0.380 | z[12] = 0.844 -0.537 |
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| x[13] = 0.907 0.420 | y[13] = 0.094 0.410 | z[13] = 0.907 0.420 |
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| x[14] = 0.137 0.991 | y[14] = 0.023 0.442 | z[14] = 0.137 0.991 |
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| x[15] = -0.760 0.650 | y[15] = -0.059 0.479 | z[15] = -0.760 0.650 |
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| x[16] = -0.958 -0.288 | y[16] = -0.161 0.525 | z[16] = -0.958 -0.288 |
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| x[17] = -0.275 -0.961 | y[17] = -0.300 0.588 | z[17] = -0.275 -0.961 |
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\endverbatim
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\author Sergey Bakhurin www.dsplib.org
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***************************************************************************** */
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#endif
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#ifdef DOXYGEN_RUSSIAN
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/*! ****************************************************************************
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\ingroup DFT_GROUP
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\brief Обратное быстрое преобразование Фурье
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Функция рассчитывает \f$ n \f$-точечное обратное быстрое преобразование Фурье
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от \f$ x(m) \f$, \f$ m = 0 \ldots n-1 \f$. \n
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\f[
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Y(k) = \frac{1}{N} \sum_{m = 0}^{n-1} x(m) \exp
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\left( j \frac{2\pi}{n} m k \right),
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\f]
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где \f$ k = 0 \ldots n-1 \f$.
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Для расчета используется алгоритм БПФ составной длины.
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\param[in] x
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Указатель на входной комплексный вектор \f$x(m)\f$,
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\f$ m = 0 \ldots n-1 \f$. \n
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Размер вектора `[n x 1]`. \n \n
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\param[in] n
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Размер ОБПФ \f$n\f$. \n
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Размер ОБПФ может быть составным вида
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\f$n = n_0 \times n_1 \times n_2 \times \ldots \times n_p \times m\f$,
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где \f$n_i = 2,3,5,7\f$, а \f$m \f$ --
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произвольный простой множитель не превосходящий 46340
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(см. описание функции \ref fft_create). \n \n
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\param[in] pfft
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Указатель на структуру `fft_t`. \n
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Указатель не должен быть `NULL`. \n
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Структура \ref fft_t должна быть предварительно однократно
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заполнена функцией \ref fft_create, и память должна быть
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очищена перед выходом функцией \ref fft_free. \n \n
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\param[out] y
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Указатель на вектор результата ОБПФ \f$Y(k)\f$,
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\f$ k = 0 \ldots n-1 \f$. Размер вектора `[n x 1]`. \n
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Память должна быть выделена. \n \n
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\return
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`RES_OK` если расчет произведен успешно. \n
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В противном случае \ref ERROR_CODE_GROUP "код ошибки". \n \n
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Пример использования функции `fft`:
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\include ifft_cmplx_test.c
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Результат работы программы:
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\verbatim
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| x[ 0] = 1.000 0.000 | y[ 0] = -0.517 0.686 | z[ 0] = 1.000 0.000 |
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| x[ 1] = 0.540 0.841 | y[ 1] = -0.943 0.879 | z[ 1] = 0.540 0.841 |
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| x[ 2] = -0.416 0.909 | y[ 2] = -2.299 1.492 | z[ 2] = -0.416 0.909 |
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| x[ 3] = -0.990 0.141 | y[ 3] = 16.078 -6.820 | z[ 3] = -0.990 0.141 |
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| x[ 4] = -0.654 -0.757 | y[ 4] = 2.040 -0.470 | z[ 4] = -0.654 -0.757 |
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| x[ 5] = 0.284 -0.959 | y[ 5] = 1.130 -0.059 | z[ 5] = 0.284 -0.959 |
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| x[ 6] = 0.960 -0.279 | y[ 6] = 0.786 0.097 | z[ 6] = 0.960 -0.279 |
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| x[ 7] = 0.754 0.657 | y[ 7] = 0.596 0.183 | z[ 7] = 0.754 0.657 |
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| x[ 8] = -0.146 0.989 | y[ 8] = 0.470 0.240 | z[ 8] = -0.146 0.989 |
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| x[ 9] = -0.911 0.412 | y[ 9] = 0.375 0.283 | z[ 9] = -0.911 0.412 |
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| x[10] = -0.839 -0.544 | y[10] = 0.297 0.318 | z[10] = -0.839 -0.544 |
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| x[11] = 0.004 -1.000 | y[11] = 0.227 0.350 | z[11] = 0.004 -1.000 |
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| x[12] = 0.844 -0.537 | y[12] = 0.161 0.380 | z[12] = 0.844 -0.537 |
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| x[13] = 0.907 0.420 | y[13] = 0.094 0.410 | z[13] = 0.907 0.420 |
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| x[14] = 0.137 0.991 | y[14] = 0.023 0.442 | z[14] = 0.137 0.991 |
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| x[15] = -0.760 0.650 | y[15] = -0.059 0.479 | z[15] = -0.760 0.650 |
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| x[16] = -0.958 -0.288 | y[16] = -0.161 0.525 | z[16] = -0.958 -0.288 |
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| x[17] = -0.275 -0.961 | y[17] = -0.300 0.588 | z[17] = -0.275 -0.961 |
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\endverbatim
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\author Бахурин Сергей www.dsplib.org
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***************************************************************************** */
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#endif
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int DSPL_API ifft_cmplx(complex_t *x, int n, fft_t* pfft, complex_t* y)
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{
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int err, k;
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double norm;
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if(!x || !pfft || !y)
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return ERROR_PTR;
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if(n<1)
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return ERROR_SIZE;
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err = fft_create(pfft, n);
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if(err != RES_OK)
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return err;
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memcpy(pfft->t1, x, n*sizeof(complex_t));
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for(k = 0; k < n; k++)
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IM(pfft->t1[k]) = -IM(pfft->t1[k]);
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err = fft_krn(pfft->t1, pfft->t0, pfft, n, 0);
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if(err!=RES_OK)
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return err;
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norm = 1.0 / (double)n;
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for(k = 0; k < n; k++)
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{
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RE(y[k]) = RE(pfft->t0[k])*norm;
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IM(y[k]) = -IM(pfft->t0[k])*norm;
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}
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return RES_OK;
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} |