From: "Michael Dinowitz" <[EMAIL PROTECTED]>
To: "CF-Talk" <[EMAIL PROTECTED]>
Sent: Wednesday, May 19, 2004 1:03 AM
Subject: Re: ad weights
> Your first solution would run into the problem of having a huge amount
of low
> ads and few high ones. Lets say a banner system has 8 free ads and 5
paying
> ones. showing the paying ones multiple times (lets say 5 per) will
result in 33
> total ads with the free ads having a 3% view rate and the pay having a
15%. Now
> take it further. 90 free ads and 2 pay ads with the pay ads having the
same 5
> per. This results in each free ad having 1% and the pay ads having 5%.
Pay ads
> are still higher, but if you look at the full numbers you see that 9
times out
> of 10 a free ad will be shown. Not very economical.
Neither were suggestions of how you should weight your ads, just how you
might approach it. Probably the only monkey wrench in your situation are
the free ads and the fact that a large number of them can take up a
disproportianate percentage of your rotation. I think you've got two
basic approaches.
One, weight the paying ads very very heavily in relation to non-paying
ads. For instance:
Ad_ID Price Weight
----- ------ ------
1 $0.00 1
2 $0.05 5000
3 $0.00 1
4 $0.01 1000
5 $5.00 500000
6 $0.25 25000
But you can still run into the problem of a very large number of the free
ads taking up perhaps more views in the rotation than you like. If that
happened you'd have to go through and further bump up the weighting of the
pay ads.
The second approach (which you hinted at in your original posting) would
be to make the weighting hierarchical. In your case you'd probably just
need two levels. At the first level create two 'groups' - paying and
non-paying ads. Throw all free ads into one group. You could weight the
ads within the free group in relation to each other, but it's probably
unnecessary and every ad could have an equal weight of '1'.
Into the second group, have your paying ads, weighted relative only to
other ads in the same group. Here you could probably just use a weighting
in proportion to the price of each - a $1.00 ad with a weight 10x that of
a $0.10 ad, for example.
Then weight the groups relative to each other. Say paying ads 75%,
non-paying 25% (or whatever). Then it doesn't matter how many non-paying
ads you have, they always take up a known percentage of the views in your
rotation. You're algorithm would make two picks - first select a group,
then select an ad within the group.
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