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| author | simon | 2008-10-27 14:18:28 +0000 |
|---|---|---|
| committer | simon | 2008-10-27 14:18:28 +0000 |
| commit | b8786359e2bd079ccfe2166bc22b6304cc4ccd02 (patch) | |
| tree | f47469beb545dc0a6220333d9042b24d0781790d /src/signalProcessing/fft/r8tx.c | |
| parent | 4e2567ecd3643cd80af11f1e939f21bf6898b4f4 (diff) | |
| download | scilab2c-b8786359e2bd079ccfe2166bc22b6304cc4ccd02.tar.gz scilab2c-b8786359e2bd079ccfe2166bc22b6304cc4ccd02.tar.bz2 scilab2c-b8786359e2bd079ccfe2166bc22b6304cc4ccd02.zip | |
added comment on code
Diffstat (limited to 'src/signalProcessing/fft/r8tx.c')
| -rw-r--r-- | src/signalProcessing/fft/r8tx.c | 27 |
1 files changed, 15 insertions, 12 deletions
diff --git a/src/signalProcessing/fft/r8tx.c b/src/signalProcessing/fft/r8tx.c index 8c44488e..bae32639 100644 --- a/src/signalProcessing/fft/r8tx.c +++ b/src/signalProcessing/fft/r8tx.c @@ -20,6 +20,9 @@ /* ** 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) @@ -65,9 +68,11 @@ void r8tx ( int nxtlt,int nthpo,int lengt, for(kk=j;kk<nthpo;kk+=lengt) { - ;/* (k-1)*2*/ /* index by twos; re & im alternate */ + /* (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] ) ; @@ -79,26 +84,24 @@ void r8tx ( int nxtlt,int nthpo,int lengt, 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 ) ); - - - 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 ) ); - - - cc0[kk] = zadds ( Btemp0 , Btemp1 ); - + /*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) { |