Re: reliable get position of leftmost bit in large integers


good chemistry is complicated, and a little bit messy -LW
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by martin (Friar)

on Mar 12, 2015 at 13:39 UTC ( [id://1119791]=note: print w/replies, xml )

Need Help??

To check whether the most significant bit positions of two unsigned integer values are equal (or both are zero), this works for me:

sub msb_pos_is_equal {
    my ($x, $y) = @_;
    ($x ^ $y) <= ($x & $y)
}
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Update: Added the words "unsigned integer" in the first paragraph.

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Re^2: reliable get position of leftmost bit in large integers by wollmers (Scribe) on Mar 12, 2015 at 14:41 UTC
Thanks. This smells very fast. I still need the value of the position, but only in case of a match, and only from one side. Then BrowserUK's solution should do it. WOW, maybe we can beat the speed of Algorithm::Diff::XS in pure Perl. Still reached 80% yesterday. Helmut Wollmersdorfer	[reply]
Re^2: reliable get position of leftmost bit in large integers by BrowserUk (Patriarch) on Mar 12, 2015 at 14:29 UTC
Nice! ++	[reply]

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