in reply to Re^2: OT: Finding Factor Closest To Square Root
in thread OT: Finding Factor Closest To Square Root

One way to do it, similar to talexb, would be (tested!) 
use Math::Big::Factors;

my $val = 2000;

my @x = Math::Big::Factors::factors_wheel( $val );
print "@x\n";

my %factors;
$factors{$_}++ for @x;

use Data::Dumper;
print Dumper \%factors;

my $sqrt = 1;
while (my ($k,$v) = each %factors) {
    while ($v > 1) {
        $sqrt *= $k;
        $v -= 2;
    }

    if ($v) {
         $sqrt *= sqrt( $k );
    }
}

print "$sqrt => ", sqrt( $val ), $/;

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This is going to be slower that just taking the sqrt of the value. Just to let you know ...

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Re^4: OT: Finding Factor Closest To Square Root
by QM (Parson) on Feb 20, 2005 at 05:08 UTC
    This would also give me a practical answer, though it could be off quite a bit for some cases.

    For instance, for N=1000, the factorization is 2**3 * 5**3. Your method gives 2**2 * 5**2 = 100, while the closest factor to the square root is 5**2 = 25 (paired with 40). I'd be happy with either 25 or 40.

    -QM
    --
    Quantum Mechanics: The dreams stuff is made of

[reply]
[d/l]
[select]
      My method actually gives 2**1.5 * 5 ** 1.5, which is the actual square root of 1000. Coming up with 25 or 40 is going to be ... interesting. I can do further research into the mathematics behind it, if you want. (Number Theory is a pet project of mine.)

      Being right, does not endow the right to be rude; politeness costs nothing.
      Being unknowing, is not the same as being stupid.
      Expressing a contrary opinion, whether to the individual or the group, is more often a sign of deeper thought than of cantankerous belligerence.
      Do not mistake your goals as the only goals; your opinion as the only opinion; your confidence as correctness. Saying you know better is not the same as explaining you know better.

[reply]
[d/l]
        I can do further research into the mathematics behind it, if you want. (Number Theory is a pet project of mine.)
        I'd be interested in any insights you have. I keep poking at number theory ideas, but I never get anywhere.

        -QM
        --
        Quantum Mechanics: The dreams stuff is made of

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