issue with output of fft

issue with output of fft

rakesh's picture

Hi,

i'm evaluating fft function.

my packed format is CCS.

i'm giving real input to fft function and i'm getting complex output arranged in real aaray in R,I,R,I format.

since it's real fft so due to conjugate symmetry i 'm getting half output.

how to retrive other half of output.

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Ying H (Intel)'s picture

Dear rakesh,

does you mean Real FFT ouput
z(n/2)
CCS
R0
0
R1
I1
...
Rn/2-1
In/2-1
Rn/2
0
and you want to restore another half
R0
0
R1
-I1
...
Rn/2-1
-In/2-1
Rn/2
0
you may use the funciton v?Conj to Performs element by element conjugation of the vector and attach another half to your original output array.

like

call vcconj( n/2, z(0), z(n/2+1) )

Best Regards,
Ying

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