evolutioner

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You're right, the paper linked above is a different way of solving the same problem. In their case they use a model to decide which website variants to show. Their model accounts for independent effects and pairwise dependencies. Evolution allows you to optimize without needing an explicit model.

I don't think they account for potentially changing conversion rates over time or delayed conversions.

Aside from that, I'd be curious to see how these two approaches compare in a real-life situation.

Comment · 8 years ago

They can actually work together.

Thompson Sampling / Multi-armed bandit algorithms are traffic allocation strategies to use the least amount of traffic to find the optimal variant.

So say you have version A/B/../N variants of a website, you can split the traffic equally or use a a bandit algorithm and find the best performing variant of it.

But that only helps you test N variants. If you want to test for 4 titles and 3 color buttons, 3 layouts and 5 images you already have 4x3x3x5=180 different variations and you can't test them all. Evolutionary algorithms can help you search through a much bigger search space:

First you try 10 variations, and allocate traffic equally or through a bandit algorithm. Then you combine the top performing candidates multiple times to create a new generation and start over again.

Evolution helps you find which candidates to try in a large search space and then a bandits algorithm can help you allocate traffic optimally.

You have to be careful with A/B testing with Bandit algorithms though. If the conversion rate changes over time or if you have visitors that don't always convert instantly you have to take that into account: https://www.chrisstucchio.com/blog/2015/dont_use_bandits.htm...

Comment · 8 years ago

Each generation has like 10~20 candidate websites. The better the conversion rate, the more likely it is to get chosen as a parent.

With your example, let's say two parents with top/blue and bottom/red are chosen, then their offspring will either be top/red or bottom/blue because we make sure the same website isn't tested twice.

More generally each feature of the offspring will be randomly picked from the features of the two parents.

So two parents A/A/B and B/C/B can give the offspring A/C/B or B/A/B. There is also some random mutations that are possible with a low likelihood.

link to the product: https://www.ascend.ai/

Comment · 8 years ago

Sentient employee here. I'll give an example on a problem for which we use evolutionary algorithms: website optimization.

Say you want to try many various changes like the title of your page, the color of the background, the position of your buy button etc. We solve this problem by trying out random variations of these websites - like A/B testing with more candidates - and by crossing the best performing ones to create a new generation of websites. This helps us find good performing variations in a very big search space.

This would be hard to do with deep learning as we start with no data at all, measuring the performance is quite noisy and you can't compute a gradient to know how to evolve your website. There is no smoothness between a title and another.

Also you could try to make a linear model for to see what effect each change has, but that doesn't take into account all the dependencies that can be complex, for example what title goes well with what background color. Evolutionary computation helps implicitly optimize without having to formulate a model.