HiFi5 NatureDSP RFFT output scaling issue for different FFT sizes

Hi,

I am working on standalone RFFT testing on Xtensa HiFi5 using the NatureDSP library.

I am testing different FFT sizes and comparing the fft_real32x32() output against my reference FFT data.

I am seeing the FFT output matches for 128, 512 and 2048 points, but does not match for 64, 256 and 1024 points.

My question is:

How should I correctly interpret/compensate the RFFT output for different FFT sizes and the returned fft_shifts value?

Is there any additional normalization or scaling required when comparing the HiFi5 fft_real32x32() output with a floating-point/reference FFT?

Also, has anyone observed this kind of behavior where:The FFT output matches for 128, 512 and 2048 points

with fft_real32x32() / ifft_real32x32() on HiFi5?

Any guidance on the correct FFT/IFFT scaling interpretation would be appreciated.

Platform: Xtensa HiFi5
Library: NatureDSP HiFi5
Functions: fft_real32x32() / ifft_real32x32()
Scaling option: 3

Thanks.