/* * 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 "ifft_internal.h" /* ** radix 4 iteration subroutine */ /* this function do in one turn the same computation that do radix 2 in two turns */ void ir4tx( int nthpo, doubleComplex* c0, doubleComplex* c1, doubleComplex* c2, doubleComplex* c3) { int kk; doubleComplex temp1 , temp2 , temp3 , temp4 ; for(kk=0;kk<nthpo;kk+=4) { /* real and imag parts alternate */ /* this first step is strictly equivalent than calling radix 2 except that radix would have needed 2 turns to compute what radix4 do in one */ temp1 = zadds ( c0[kk] , c2[kk] ) ; temp2 = zdiffs( c0[kk] , c2[kk] ) ; temp3 = zadds ( c1[kk] , c3[kk] ) ; temp4 = zdiffs( c1[kk] , c3[kk] ) ; /* strictly equivalent than calling radix2 with the temporary vector , but here also , radix4 do it in one turn instead of two */ c0[kk] = zadds ( temp1 , temp3 ); c1[kk] = zdiffs( temp1 , temp3 ); c2[kk] = DoubleComplex ( zreals ( temp2 ) - zimags( temp4 ) , zimags ( temp2 ) + zreals( temp4 ) ); c3[kk] = DoubleComplex ( zreals ( temp2 ) + zimags( temp4 ) , zimags ( temp2 ) - zreals( temp4 ) ); } }