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Cooperative Coevolution typo


Whilst re-implementing the paper “A Cooperative Coevolutionary Approach to Function Optimization” by Mitchell Potter and Kenneth De Jong for a Computer Science assignment, I noticed a typo in one of the benchmark functions.

In the paper, the Schwefel function is listed on page 5 as

f(x) = 418.9829n + sum(x_i * sin(sqrt(abs(x_i))))

but the actual function is

f(x) = 418.9829n - sum(x_i * sin(sqrt(abs(x_i))))

Notice the sign change in the middle.

I have found 3 references that back this up:

It’s probably also worth noting that one of these sources give the constant to a greater accuracy; 418.982887.