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/*
* Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
* Copyright (C) 2008 - INRIA - Allan SIMON
*
* This file must be used under the terms of the CeCILL.
* This source file is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at
* http://www.cecill.info/licences/Licence_CeCILL_V2-en.txt
*
*/
#include "fft_internal.h"
#include <math.h>
/*
** radix 8 iteration subroutine
*/
/* this function do in one turn the same computation that do radix 2 in three turns */
void r8tx ( int nxtlt,int nthpo,int lengt,
doubleComplex* cc0,doubleComplex* cc1,doubleComplex* cc2,doubleComplex* cc3,
doubleComplex* cc4,doubleComplex* cc5,doubleComplex* cc6,doubleComplex* cc7)
{
int j , kk;
double dblP7 = 1 / sqrt(2.0) ;
double dblPi2 = 8 * atan(1.0);
double scale, arg;
double c1,c2,c3,c4,c5,c6,c7;
double s1,s2,s3,s4,s5,s6,s7;
doubleComplex Atemp0,Atemp1,Atemp2,Atemp3,Atemp4,Atemp5,Atemp6,Atemp7;
doubleComplex Btemp0,Btemp1,Btemp2,Btemp3,Btemp4,Btemp5,Btemp6,Btemp7;
doubleComplex temp ;
scale = dblPi2/lengt;
for(j=0;j<nxtlt;j++)
{
arg = j*scale;
c1 = cos(arg);
s1 = sin(arg);
c2 = c1*c1 - s1*s1;
s2 = c1*s1 + c1*s1;
c3 = c1*c2 - s1*s2;
s3 = c2*s1 + s2*c1;
c4 = c2*c2 - s2*s2;
s4 = c2*s2 + c2*s2;
c5 = c2*c3 - s2*s3;
s5 = c3*s2 + s3*c2;
c6 = c3*c3 - s3*s3;
s6 = c3*s3 + c3*s3;
c7 = c3*c4 - s3*s4;
s7 = c4*s3 + s4*c3;
for(kk=j;kk<nthpo;kk+=lengt)
{
/* (k-1)*2*/ /* index by twos; re & im alternate */
/* first turn the same as calling radix 2 with the input vector */
/* but radix2 will have do it in three turn , radix8 do it in one */
Atemp0 = zadds ( cc0[kk] , cc4[kk] ) ;
Atemp1 = zadds ( cc1[kk] , cc5[kk] ) ;
Atemp2 = zadds ( cc2[kk] , cc6[kk] ) ;
Atemp3 = zadds ( cc3[kk] , cc7[kk] ) ;
Atemp4 = zdiffs ( cc0[kk] , cc4[kk] ) ;
Atemp5 = zdiffs ( cc1[kk] , cc5[kk] ) ;
Atemp6 = zdiffs ( cc2[kk] , cc6[kk] ) ;
Atemp7 = zdiffs ( cc3[kk] , cc7[kk] ) ;
/* second turn the same as calling radix 2 with the vector transformed by a previous call of radix2 */
/* the same here , three turns in one */
Btemp0 = zadds ( Atemp0 , Atemp2 ) ;
Btemp1 = zadds ( Atemp1 , Atemp3 ) ;
Btemp2 = zdiffs ( Atemp0 , Atemp2 ) ;
Btemp3 = zdiffs ( Atemp1 , Atemp3 ) ;
Btemp4 = DoubleComplex ( zreals ( Atemp4 ) - zimags( Atemp6 ) , zimags ( Atemp4 ) + zreals( Atemp6 ) );
Btemp5 = DoubleComplex ( zreals ( Atemp5 ) - zimags( Atemp7 ) , zimags ( Atemp5 ) + zreals( Atemp7 ) );
Btemp6 = DoubleComplex ( zreals ( Atemp4 ) + zimags( Atemp6 ) , zimags ( Atemp4 ) - zreals( Atemp6 ) );
Btemp7 = DoubleComplex ( zreals ( Atemp5 ) + zimags( Atemp7 ) , zimags ( Atemp5 ) - zreals( Atemp7 ) );
/*third turn the same as calling radix 2 with the vector transformed by two previous call of radix2 */
cc0[kk] = zadds ( Btemp0 , Btemp1 );
/* if we are not in the first turn */
if(j>0)
{
cc1[kk] = DoubleComplex ( (c4 * (zreals(Btemp0) - zreals(Btemp1))) - (s4 * (zimags(Btemp0) - zimags(Btemp1))),
c4 * (zimags(Btemp0) - zimags(Btemp1)) + s4 * (zreals(Btemp0) - zreals(Btemp1)));
cc2[kk] = DoubleComplex ( c2 * (zreals(Btemp2) - zimags(Btemp3)) - s2 * (zimags(Btemp2) + zreals(Btemp3)) ,
c2 * (zimags(Btemp2) + zreals(Btemp3)) + s2 * (zreals(Btemp2) - zimags(Btemp3)));
cc3[kk] = DoubleComplex ( c6 * (zreals(Btemp2) + zimags(Btemp3)) - s6 * (zimags(Btemp2) - zreals(Btemp3)) ,
c6 * (zimags(Btemp2) - zreals(Btemp3)) + s6 * (zreals(Btemp2) + zimags(Btemp3)));
temp = DoubleComplex ( dblP7*(zreals ( Btemp5 ) - zimags( Btemp5 )) ,
dblP7*(zreals ( Btemp5 ) + zimags( Btemp5 )) );
cc4[kk] = DoubleComplex ( c1 * (zreals (Btemp4) + zreals(temp)) - s1 * (zimags (Btemp4) + zimags(temp)) ,
c1 * (zimags (Btemp4) + zimags(temp)) + s1 * (zreals (Btemp4) + zreals(temp)));
cc5[kk] = DoubleComplex ( c5 * (zreals (Btemp4) - zreals(temp)) - s5 * (zimags (Btemp4) - zimags(temp)) ,
c5 * (zimags (Btemp4) - zimags(temp)) + s5 * (zreals (Btemp4) - zreals(temp)));
temp = DoubleComplex ( - dblP7*(zreals ( Btemp7 ) + zimags( Btemp7 )) ,
dblP7*(zreals ( Btemp7 ) - zimags( Btemp7 )) );
cc6[kk] = DoubleComplex ( c3 * (zreals (Btemp6) + zreals(temp)) - s3 * (zimags (Btemp6) + zimags(temp)) ,
c3 * (zimags (Btemp6) + zimags(temp)) + s3 * (zreals (Btemp6) + zreals(temp)));
cc7[kk] = DoubleComplex ( c7 * (zreals (Btemp6) - zreals(temp)) - s7 * (zimags (Btemp6) - zimags(temp)) ,
c7 * (zimags (Btemp6) - zimags(temp)) + s7 * (zreals (Btemp6) - zreals(temp)));
}
else
{
cc1[kk] = zdiffs ( Btemp0 , Btemp1 );
cc2[kk] = DoubleComplex ( zreals ( Btemp2 ) - zimags( Btemp3 ) ,
zimags ( Btemp2 ) + zreals( Btemp3 ) );
cc3[kk] = DoubleComplex ( zreals ( Btemp2 ) + zimags( Btemp3 ) ,
zimags ( Btemp2 ) - zreals( Btemp3 ) );
temp = DoubleComplex ( dblP7*(zreals ( Btemp5 ) - zimags( Btemp5 )) ,
dblP7*(zreals ( Btemp5 ) + zimags( Btemp5 )) );
cc4[kk] = zadds ( Btemp4 , temp );
cc5[kk] = zdiffs ( Btemp4 , temp );
temp = DoubleComplex ( - dblP7*(zreals ( Btemp7 ) + zimags( Btemp7 )) ,
dblP7*(zreals ( Btemp7 ) - zimags( Btemp7 )) );
cc6[kk] = zadds ( Btemp6 , temp );
cc7[kk] = zdiffs ( Btemp6 , temp );
}
}
}
}
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