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2 pj 1
 
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/*
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 * Copyright (c) 1997-1999 Massachusetts Institute of Technology
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 *
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 * This program is free software; you can redistribute it and/or modify
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 * it under the terms of the GNU General Public License as published by
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 * the Free Software Foundation; either version 2 of the License, or
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 * (at your option) any later version.
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 *
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 * This program 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 General Public License
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 * along with this program; if not, write to the Free Software
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 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
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 *
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 */
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/*
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 * rgeneric.c -- "generic" rfftw codelets.  They work for all n (and
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 * they are slow)
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 */
107 pj 25
#include <fftw-int.h>
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#include <rfftw.h>
2 pj 27
 
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/* this code assumes that r and m are both odd */
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void fftw_hc2hc_forward_generic(fftw_real *A, const fftw_complex *W,
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                                int m, int r, int n, int dist)
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{
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     int i, j, k;
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     fftw_complex *tmp = (fftw_complex *)
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     fftw_malloc(r * sizeof(fftw_complex));
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     fftw_real rsum, isum;
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     fftw_real *X, *YO, *YI;
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     int wp, wincr;
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     int iostride = m * dist;
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     X = A;
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     YO = A + r * iostride;
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     YI = A + iostride;
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     /* compute the transform of the r 0th elements (which are real) */
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     for (i = 0; i + i < r; ++i) {
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          rsum = 0.0;
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          isum = 0.0;
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          wincr = m * i;
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          for (j = 0, wp = 0; j < r; ++j) {
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               fftw_real tw_r = c_re(W[wp]);
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               fftw_real tw_i = c_im(W[wp]);
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               fftw_real re = X[j * iostride];
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               rsum += re * tw_r;
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               isum += re * tw_i;
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               wp += wincr;
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               if (wp >= n)
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                    wp -= n;
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          }
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          c_re(tmp[i]) = rsum;
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          c_im(tmp[i]) = isum;
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     }
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     /* store the transform back onto the A array */
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     X[0] = c_re(tmp[0]);
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     for (i = 1; i + i < r; ++i) {
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          X[i * iostride] = c_re(tmp[i]);
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          YO[-i * iostride] = c_im(tmp[i]);
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     }
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     X += dist;
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     YI -= dist;
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     YO -= dist;
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     /* compute the transform of the middle elements (which are complex) */
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     for (k = 1; k + k < m; ++k, X += dist, YI -= dist, YO -= dist) {
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          for (i = 0; i < r; ++i) {
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               rsum = 0.0;
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               isum = 0.0;
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               wincr = k + m * i;
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               for (j = 0, wp = 0; j < r; ++j) {
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                    fftw_real tw_r = c_re(W[wp]);
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                    fftw_real tw_i = c_im(W[wp]);
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                    fftw_real re = X[j * iostride];
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                    fftw_real im = YI[j * iostride];
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                    rsum += re * tw_r - im * tw_i;
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                    isum += re * tw_i + im * tw_r;
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                    wp += wincr;
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                    if (wp >= n)
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                         wp -= n;
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               }
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               c_re(tmp[i]) = rsum;
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               c_im(tmp[i]) = isum;
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          }
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          /* store the transform back onto the A array */
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          for (i = 0; i + i < r; ++i) {
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               X[i * iostride] = c_re(tmp[i]);
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               YO[-i * iostride] = c_im(tmp[i]);
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          }
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          for (; i < r; ++i) {
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               X[i * iostride] = -c_im(tmp[i]);
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               YO[-i * iostride] = c_re(tmp[i]);
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          }
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     }
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     /* no final element, since m is odd */
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     fftw_free(tmp);
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}
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void fftw_hc2hc_backward_generic(fftw_real *A, const fftw_complex *W,
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                                 int m, int r, int n, int dist)
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{
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     int i, j, k;
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     int wp, wincr;
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     fftw_complex *tmp = (fftw_complex *)
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     fftw_malloc(r * sizeof(fftw_complex));
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     fftw_real rsum, isum;
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     fftw_real *X, *YO, *YI;
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     int iostride = m * dist;
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     X = A;
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     YO = A + iostride;
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     YI = A + r * iostride;
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     /*
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      * compute the transform of the r 0th elements (which are halfcomplex)
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      * yielding real numbers
126
      */
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     /* copy the input into the temporary array */
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     c_re(tmp[0]) = X[0];
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     for (i = 1; i + i < r; ++i) {
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          c_re(tmp[i]) = X[i * iostride];
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          c_im(tmp[i]) = YI[-i * iostride];
132
     }
133
 
134
     for (i = 0; i < r; ++i) {
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          rsum = 0.0;
136
          wincr = m * i;
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          for (j = 1, wp = wincr; j + j < r; ++j) {
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               fftw_real tw_r = c_re(W[wp]);
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               fftw_real tw_i = c_im(W[wp]);
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               fftw_real re = c_re(tmp[j]);
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               fftw_real im = c_im(tmp[j]);
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               rsum += re * tw_r + im * tw_i;
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               wp += wincr;
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               if (wp >= n)
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                    wp -= n;
146
          }
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          X[i * iostride] = 2.0 * rsum + c_re(tmp[0]);
148
     }
149
 
150
     X += dist;
151
     YI -= dist;
152
     YO -= dist;
153
 
154
     /* compute the transform of the middle elements (which are complex) */
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     for (k = 1; k + k < m; ++k, X += dist, YI -= dist, YO -= dist) {
156
          /* copy the input into the temporary array */
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          for (i = 0; i + i < r; ++i) {
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               c_re(tmp[i]) = X[i * iostride];
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               c_im(tmp[i]) = YI[-i * iostride];
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          }
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          for (; i < r; ++i) {
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               c_im(tmp[i]) = -X[i * iostride];
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               c_re(tmp[i]) = YI[-i * iostride];
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          }
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166
          for (i = 0; i < r; ++i) {
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               rsum = 0.0;
168
               isum = 0.0;
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               wincr = m * i;
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               for (j = 0, wp = k * i; j < r; ++j) {
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                    fftw_real tw_r = c_re(W[wp]);
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                    fftw_real tw_i = c_im(W[wp]);
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                    fftw_real re = c_re(tmp[j]);
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                    fftw_real im = c_im(tmp[j]);
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                    rsum += re * tw_r + im * tw_i;
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                    isum += im * tw_r - re * tw_i;
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                    wp += wincr;
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                    if (wp >= n)
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                         wp -= n;
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               }
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               X[i * iostride] = rsum;
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               YO[i * iostride] = isum;
183
          }
184
     }
185
 
186
     /* no final element, since m is odd */
187
     fftw_free(tmp);
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}