From: supergems on 9 Apr 2010 03:44 Hi, how can we calculate the Hamming distance ( http://en.wikipedia.org/wiki/Hamming_distance ) between two binary numbers? For example, the Hamming distance between 1011101 and 1001001 is 2. supergems
From: supergems on 9 Apr 2010 03:45 Obviously with the HP 50g ;)
From: Teuvo Yrjömäki on 9 Apr 2010 05:52 a quick try, works at least for some numbers... << 0 > acc << dup2 b>r .001 + log 2 log / ip swap b>r .001 + log 2 log / ip max 0 swap 1 + for x dup2 #1b and swap #1b and if /= then acc 1 + 'acc' sto end sr swap sr next drop2 acc >> >> supergems schreef: > Hi, how can we calculate the Hamming distance ( http://en.wikipedia.org/wiki/Hamming_distance > ) between two binary numbers? For example, the Hamming distance > between 1011101 and 1001001 is 2. > > supergems >
From: Dave Hayden on 9 Apr 2010 07:00 On Apr 9, 3:44 am, supergems <simone.cer...(a)gmail.com> wrote: > Hi, how can we calculate the Hamming distance (http://en.wikipedia.org/wiki/Hamming_distance > ) between two binary numbers? For example, the Hamming distance > between 1011101 and 1001001 is 2. > > supergems Given two binary numbers A and B, then Hamming distance is the number of "1" bits in (A AND B). Here's a library that will count the bits: http://www.hpcalc.org/details.php?id=2752 There are some REALLY clever ways to count bits. This site lists many of them: http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetNaive If you expect the Hamming distance to be small, then Brian Kernighan's method would be a good choice. It's very small and the run time and proportional to the number of bits that are set. In C code: unsigned int v; // count the number of bits set in v unsigned int c; // c accumulates the total bits set in v for (c = 0; v; c++) { v &= v  1; // clear the least significant bit set }
From: Michael J. Sch�lke on 9 Apr 2010 08:29 Dave Hayden schrieb: > Given two binary numbers A and B, then Hamming distance is the number > of "1" bits in (A AND B). A XOR B, surely? Regards, Michael

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