February 2008


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Johanna Rosenbusch <[log in to unmask]>
Reply To:
ECJ Evolutionary Computation Toolkit <[log in to unmask]>
Tue, 12 Feb 2008 18:53:48 +0100
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Hello everybody,

I have a question concerning the fitness evaluation (in coevolution).

I want to do worst case optimization and I am testing my solutions
(population 1) against scenarios (population 2). The fitness of my solutions
is quite easy to determine - it's the worst outcome of the interactions and
I can more or less use SimpleFitness. The fitness of the scenarios is more
difficult to determine - which is why I would like to test a few ideas
before deciding on one.
Therefore I need to define a new fitness and I am wondering where to start.
The fitness of one scenario depends not only on the outcome of the
interactions with the solutions but also on the performance of the other
scenarios. For example:

Imagine each solution is tested against each scenario and then lists the
scenarios according to the results. The worst case scenario for example
would get the highest rank. Now the fitness of a scenario is equal to the
highest rank it achieves for any rule.

You see, I need quite a lot of information and before I started using ECJ I
imagined I would first do all the interactions, get a matrix of the results,
and then compute the fitness values. Now I found out that in ECJ the fitness
is actually computed during the interaction of two individuals. Where in the
algorithm do I have access to the information I need and can define the
fitness accordingly? As it seems to me, I cannot do it just by modifying

Thanks for every comment!