On 11/1/07, Ray S <[EMAIL PROTECTED]> wrote: > > At 09:00 AM 11/1/2007, Chuck wrote: > > In Python, collections.deque makes a pretty good circular buffer. > Numpy will > make an array out of it, which involves a copy, but it might be > better than what you are doing now. > > hmmm, I'll think more about that - and the copy is only at program > start, it seems > the fft can always be fft(d[:-N]) > >>> from collections import deque > >>> import numpy as N > >>> d = deque(N.zeros(10,)) > >>> d.extend(N.ones(4,)) > >>> d > deque([0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0, 1.0, > 1.0, 1.0]) > >>> [d.pop() for i in range(4)] > [1.0, 1.0, 1.0, 1.0]
Yeah, I noticed that inconvenience. >>> d > deque([0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]) > > An additional complication is that I pass the numpy (or Numeric) > array address to the ctypes library call so that the data is placed > directly into the array from the call. I use the if/else end wrap > logic to determine whether I need to do a split and copy if the new > data wraps. OK. Hmm, I wonder if you would lose much by taking a straight forward radix-2 fft and teaching it to use modular indices? Probably not worth the trouble, but an fft tailored to a ring buffer might be useful for other things. Probably the easiest thing is to just copy the ring buffer out into a linear array. Chuck
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