Hamming Distance
John Machin
sjmachin at lexicon.net
Fri Jun 20 01:51:10 CEST 2008
On Jun 20, 9:27 am, godavemon <davefow... at gmail.com> wrote:
> I need to calculate the Hamming Distance of two integers. The hamming
> distance is the number of bits in two integers that don't match. I
> thought there'd be a function in math or scipy but i haven't been able
> to find one. This is my function but it seems like there should be a
> faster way. I do this computation many times and speed up is
> important.
>
> def hamdist( a, b , bits = 32):
> def _hamdist( x, bits):
> if bits:
> return (x & 1) + _hamdist(x >> 1, bits-1)
> return x & 1
> return _hamdist( a ^ b, bits)
>
> Another alternative would be to convert the XOR to a binary string and
Isn't it a "binary string" already?
> count the # of 1's.
My guess is that counting the 1-bits in (a ^ b) would be hard to beat,
and that a recursive function is just not in the race.
>
> Which would be fastest?
Implement both and time them.
> Are there better alternatives?
I doubt it.
BTW one presumes that your integers are non-negative ...
HTH
Cheers,
John
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