kopia lustrzana https://github.com/Dsplib/libdspl-2.0
253 wiersze
8.2 KiB
C
253 wiersze
8.2 KiB
C
/*
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* Copyright (c) 2015-2019 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 <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "dspl.h"
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#ifdef DOXYGEN_ENGLISH
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/*! ****************************************************************************
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\ingroup IIR_FILTER_DESIGN_GROUP
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\fn int butter_ap_zp(int ord, double rp, complex_t* z, int* nz,
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complex_t* p, int* np)
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\brief
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Function calculates arrays of zeros and poles for analog normlized lowpass
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Batterworth filter transfer function \f$ H(s) \f$ order `ord` .
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Analog normalized lowpass filter magnitude ripple equals \f$ -R_p \f$ dB
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for angular frequency \f$ \omega \f$ from 0 to 1 rad/s.
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\param[in] ord
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Filter order. \n
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Number of zeros and poles of filter can be less or equal `ord`. \n
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\n
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\param[in] rp
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Magnitude ripple in passband (dB). \n
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This parameter sets maximum filter distortion from 0 to 1 rad/s frequency. \n
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Parameter must be positive. \n
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\n
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\param[out] z
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Pointer to the \f$ H(s) \f$ zeros array. \n
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Maximum vector size is `[ord x 1]`. \n
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Memory must be allocated for maximum vector size. \n
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\n
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\param[out] nz
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Pointer to the variable which keep number of finite zeros \f$ H(s) \f$. \n
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Number of finite zeros which was calculated and saved in vector `z`. \n
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Pointer cannot be `NULL`. \n
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\n
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\param[out] p
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Pointer to the \f$ H(s) \f$ poles array. \n
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Maximum vector size is `[ord x 1]`. \n
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Memory must be allocated for maximum vector size. \n
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\n
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\param[out] np
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Pointer to the variable which keep number of
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calculated poles of \f$ H(s) \f$. \n
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Pointer cannot be `NULL`. \n
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\n
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\return
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`RES_OK` if zeros and poles is calculated successfully. \n
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Else \ref ERROR_CODE_GROUP "code error".
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\n
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\note
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Normalized Butterworth lowpass filter has no finite zeros.
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So `z` vector will not changed and in pointer `nz` will write 0 value. \n
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Example of normalized Butterworth lowpass filter zeros and poles calculation:
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\include butter_ap_zp_test.c
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Result:
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\verbatim
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Butterworth filter zeros: 0
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Butterworth filter poles: 7
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p[ 0] = -1.101 +0.000 j
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p[ 1] = -0.245 +1.074 j
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p[ 2] = -0.245 -1.074 j
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p[ 3] = -0.687 +0.861 j
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p[ 4] = -0.687 -0.861 j
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p[ 5] = -0.992 +0.478 j
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p[ 6] = -0.992 -0.478 j
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\endverbatim
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\n
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In `dat` folder will be created `butter_ap_zp.txt` file. \n
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In addition, GNUPLOT will build the following graphs
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from data stored in `dat/butter_ap_zp.txt` file:
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\image html butter_ap_zp_test.png
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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 IIR_FILTER_DESIGN_GROUP
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\fn int butter_ap_zp(int ord, double rp, complex_t* z, int* nz,
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complex_t* p, int* np)
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\brief
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Расчет массивов нулей и полюсов передаточной функции
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\f$ H(s) \f$ аналогового нормированного ФНЧ Баттерворта.
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Функция рассчитывает значения нулей и полюсов передаточной функции
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\f$ H(s)\f$ аналогового нормированного ФНЧ Баттерворта порядка `ord`
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с частотой среза 1 рад/с по уровню \f$-R_p\f$ дБ. \n
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\param[in] ord
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Порядок фильтра. \n
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\n
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\param[in] rp
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Неравномерность АЧХ в полосе пропускания (дБ). \n
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Параметр задает уровень искажений в полосе от 0 до 1 рад/с. \n
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Значение должно быть положительным. \n
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\n
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\param[out] z
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Указатель на массив комплексных нулей
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передаточной характеристики \f$ H(s)\f$. \n
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Максимальный размер вектора вектора `[ord x 1]`. \n
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Память должна быть выделена. \n
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\n
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\param[out] nz
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Указатель на переменную количества нулей
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передаточной характеристики \f$ H(s)\f$. \n
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По данному указателю будет записано количество
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нулей фильтра, которые были рассчитаны и
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помещены в вектор `z`. \n
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Память должна быть выделена. \n
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\n
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\param[out] p
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Указатель на массив комплексных полюсов
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передаточной характеристики \f$ H(s)\f$. \n
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Максимальный размер вектора вектора `[ord x 1]`. \n
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Память должна быть выделена. \n
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\n
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\param[out] np
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Указатель на переменную количества полюсов
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передаточной характеристики \f$ H(s)\f$. \n
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По данному укащзателю будет записано количество нулей фильтра, которые
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были рассчитны и помещены в вектор `p`. \n
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Память должна быть выделена. \n
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\n
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\return
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`RES_OK` --- массивы нулей и полюсов рассчитаны успешно. \n
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В противном случае \ref ERROR_CODE_GROUP "код ошибки". \n
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\n
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\note
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Нормированный ФНЧ Баттерворта не имеет нулей, поэтому массив нулей `z`
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не будет изменен, а по указателю `nz` будет записан 0. \n
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Пример программы рассчета нулей и полюсов нормированного ФНЧ Баттерворта:
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\include butter_ap_zp_test.c
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Результат выполнения программы:
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\verbatim
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Butterworth filter zeros: 0
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Butterworth filter poles: 7
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p[ 0] = -1.101 +0.000 j
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p[ 1] = -0.245 +1.074 j
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p[ 2] = -0.245 -1.074 j
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p[ 3] = -0.687 +0.861 j
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p[ 4] = -0.687 -0.861 j
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p[ 5] = -0.992 +0.478 j
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p[ 6] = -0.992 -0.478 j
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\endverbatim
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\n
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В каталоге `dat` будет создан файл `butter_ap_zp.txt`. \n
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Пакет GNUPLOT произведет построение карты полюсов по
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сохранненным в `dat/butter_ap_zp.txt` данным:
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\image html butter_ap_zp_test.png
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\author
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Бахурин Сергей
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www.dsplib.org
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***************************************************************************** */
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#endif
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int DSPL_API butter_ap_zp(int ord, double rp, complex_t* z, int* nz,
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complex_t *p, int* np)
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{
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double alpha;
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double theta;
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double ep;
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int r;
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int L;
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int ind = 0, k;
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if(rp < 0 || rp == 0)
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return ERROR_FILTER_RP;
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if(ord < 1)
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return ERROR_FILTER_ORD;
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if(!z || !p || !nz || !np)
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return ERROR_PTR;
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ep = sqrt(pow(10.0, rp*0.1) - 1.0);
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r = ord % 2;
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L = (int)((ord-r)/2);
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alpha = pow(ep, -1.0/(double)ord);
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if(r)
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{
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RE(p[ind]) = -alpha;
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IM(p[ind]) = 0.0;
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ind++;
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}
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for(k = 0; k < L; k++)
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{
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theta = M_PI*(double)(2*k + 1)/(double)(2*ord);
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RE(p[ind]) = RE(p[ind+1]) = -alpha * sin(theta);
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IM(p[ind]) = alpha * cos(theta);
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IM(p[ind+1]) = -alpha * cos(theta);
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ind+=2;
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}
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*np = ord;
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*nz = 0;
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return RES_OK;
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}
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