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I'm no probabalist, but your code seems on the ball to me. Here's an alternative method I use from time to time that doesn't require the creation of an additional accumulating-weight array:
sub choose_weighted { my $weights = shift; my $total = 0; $total += $_ for @$weights; my $rand_val = $total * rand; my $i = -1; $rand_val -= $weights->[++$i] while ($rand_val > 0); return $i; }

  1. Pick a random number less than the total
  2. At each position of the array, subtract the weight at that position
  3. When the result is negative, return that position

I have found this algorithm easier to adapt for multiple selections, i.e., calling choose_weighted( [1.75, 2, 3.6, 4], 2 ) and getting back two (different) numbers randomly chosen with this weighting. However, once you start doing this, you have to modify the array of weights (each time you select an item, set its weight to zero and subtract accordingly from $total), which may be undesired here.

Cheers,

blokhead


In reply to Re: Weighted random numbers generator by blokhead
in thread Weighted random numbers generator by spurperl

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    [davido]: /var/run/utmp is 664 i think.
    [tye]: Note that my "man getlogin" says that it uses stdin when it should use /dev/tty (calling a glibc bug). But that does not appear to be the case when I test it. But maybe Perl's getlogin() is not using glibc's getlogin().
    [oiskuu]: well, run a strace and see what the getlogin does for you.... As I said. SELinux probably has those security labels. But not regular linux.
    [tye]: for example, read https://unix. stackexchange.com/ questions/146138/ loginuid-should-be -allowed-to-change -or-not-mutable-or -not
    [tye]: I'm not using SELinux and it certainly appears to disagree with you. shrug
    [tye]: Since you brought up /proc, oiskuu, I didn't see you respond to my suggestion of 'loginuid'. Does your /proc not have such?

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