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functions in convol.i -
convol
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convol(a,b)
returns convolution of vector a with vector b, a vector
of length na+nb-1 where na=numberof(a), nb=numberof(b).
In detail, for i=[1 to na+nb-1]
result(i) = sum j=[max(1,1+i-nb) to min(na,i)] (a(j)*b(1+i-j))
The n0= and n1= keywords can be used to control the section of
the full array that is actually returned, 1<=n0
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SEE ALSO:
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fft_good,
fft
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fft_good
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fft_good(n)
returns the smallest number of the form 2^x*3^y*5^z greater
than or equal to n. An fft of this length will be much faster
than a number with larger prime factors; the speed difference
can be an order of magnitude or more.
For n>100, the worst cases result in a little over a 11% increase
in n; for n>1000, the worst are a bit over 6%; still larger n are
better yet. The median increase for n<=10000 is about 1.5%.
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SEE ALSO:
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fft,
fft_setup,
convol
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