Generate a "random" number with specific weight
Anyone knows/suggests the logic to get a random number with some specific weights?
A clear example: banner serving, from a banner pool, you get a banner, and that banner has a weight.
One solution I've seen: create an array with the heavier elements have more copies in the array.
So that: a banner with weight 10 and there are 10 other banners with weight 1, the pool banner will have 11 elements, and the banner with weight 10 appears 10 times!
What I want to ask is another solution(or algorithm)? Or is this one the best algorithm?
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Son
richjb posted this at 04:43 — 11th August 2000.
They have: 193 posts
Joined: Feb 2000
Recipe 2.11 of the CGI/PERL Cookbook covers what you want to do...but I'm not sure of how it works, and am not sure if I can post the code.
Richard
[email protected]
Everyone here has a website. It's just that not all are worth posting (Mine!
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123finder.com posted this at 05:06 — 11th August 2000.
They have: 60 posts
Joined: Aug 2000
I don't have that book, so if you have time, please grasp the basic idea. I really love to know it!!
I don't need the code, since I think I might code it in PHP. The algorithm is most important for me. Thanks for your help in advance!
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Son
richjb posted this at 06:00 — 11th August 2000.
They have: 193 posts
Joined: Feb 2000
To tell the truth, I'm having a lot of problems trying to...don't get me wrong; I'm good at PERL, but as a CGI language, and not as just a regular one. This book takes for granted that I am used to typing ym code right into the interpretuer (sp?), which I'm not. I've been trying to figure this out since you posted your message a few days ago.
You said you didn't want to code but that's the best I could to (I found the info online somewhere, but lost it, otherwise I would point you to that):
sub weight_to_dist {
my %weights = @_;
my %dist = ();
my $total = 0;
my ($key, $weight);
local $_;
foreach (values %weights) {
$total += $_;
}
while ( ($key, $weight) = each %weights ) {
$dist{$key} = $weight/$total;
}
return %dist;
}
sub weighted_rand {
my %dist = @_;
my ($key, $weight);
while (1) {
my $rand = rand;
while ( ($key, $weight) = each %dist ) {
return $key if (rand -= $weight) < 0;
}
}
}
I don't know what to pass to it (I tried several things, none worked), and my best guys is that $key is the rand number it produces. If you figure anything out, please tell me!
Richard
[email protected]
Everyone here has a website. It's just that not all are worth posting (Mine!
).
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