I can't say about the performance per se (I'm actually quite surprised that would be noticably slow unless you're running it a lot of times, since you'll only create a total of 100 entries), but I can say that your design appears to have some serious problems. One of the main ones is that you're using the percentages as keys to a hash, so no two advertisers can have the same percentage (or the second one would disappear entirely). Once you create
@ary, do you only use it once? If so, then you might look at
Weighted random numbers generator. If you are going to use it several times, you still might do better to reverse the direction of your hash, if you even need the hash at all--is there a reason for it?
