On Dec 11, 2009, at 4:30 PM, Jeffrey J. Early wrote:
2. One issue with making a single FFT interface appears to be
interleaved versus non-interleaved types (is this true? I don't
actually know much about the FFT implementations themselves, but
this is certainly true of the interfaces). When I moved my code from
the Accelerate FFT to the MatrixFFT implementation with my existing
code, I got about a 2-fold speedup (rather than the 10-fold I saw in
the 'pure' test, despite FFTs being my speed limiter). Doing some
basic performance testing and it appears that the limiting issue is
that now I'm forced to convert the non-interleaved DSPSplitComplex
types into the interleaved FFTComplex type (fftVDSPToInt and
fftIntToVDSP). I could go back and convert the rest of my code to
interleaved types, but is this a waste of time? What the best
approach here?
MatrixFFT can use both interleaved and split (vDSP-style) complex
data. It's a compile-time configuration switch; see libMatrixFFT/
MatrixFFTConfig.h. In some cases MatrixFFT performs better with
interleaved complex data, but if you have code that already uses vDSP-
style complex then you're probably better off just configuring
MatrixFFT for split complex.
--dpm
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