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 | |
SEE ALSO: | fft_good, fft |
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%. | |
SEE ALSO: | fft, fft_setup, convol |