Hi Danilo Good thoughts and points.
while on the RAM subject : require reading for every serious programmer : "Memory" https://lwn.net/Archives/GuestIndex/#Drepper_Ulrich read all 7 parts, 100 pages, but if you only have an hour, just read "part 2 - cache" On the fft: I am not surprised that the ARM lib hand optimized assembler is that much faster. more that 2x faster.... in fact. I don't think kiss-fft is particular suitable for this sort of platform, either, I'll hold back what I really think :-) . The 5WS on flash (actually 6WS I am running @ 168M) does not really affect the performance too much. In fact I can vary the WS count +/- 2 without much change- the ART and the prefetch and the instruction and data caches are doing their job, so there is very little difference with the const values in ram or cache. In fact, most FFT implementations are very tough on a machine with cache . Have you read the paper on how FFTW works ? It is very cache aware- and adaptive to the architecture- that is why it does trial runs and picks the best. The M7 is very impressive. It is certainly impressive work by ARM. However, the M4 is what all of you have to work with so we can stay focussed on that. I think also the ram usage will be significantly less with the arm FFT because of the re-entrant Kiss-fft behaviour. The m4 is quite a different beast, and no D-cache can improve performance over the M7 for some (inaptly) written applications (not this one- but as a generalization for applications grabbing a byte from memory randomly and all over a large dataset) Large matrix operations are where cache machines fall over- that is once the dataset is bigger than the cache.... The question is how much optimization is enough. I am tempted NOT to optimize any more, although I feel (just by looking at it ) I can get another 2x out of it..... Why- well there is no real pressing need. Going too far away from the reference code will island the code a bit. However, if you run out of modem cycles/ modem ram, then we can probably get a bit more... cheers ------------------------------------------------------------------------------ _______________________________________________ Freetel-codec2 mailing list Freetel-codec2@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freetel-codec2
