'I Eat Bugs for Breakfast'

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Permalink Reply by David Rutten on April 17, 2012 at 11:09am

Hi Wade,

you're probably better off not changing the default of 25%. Here's what this settings means though.

The Annealing Solver operates by jumping through the Fitness Landscape at ever decreasing step-sizes. It starts out with large jumps, then as it cools the jumps get smaller and smaller as does the likelihood of a retrograde jump being accepted as a valid new state.

Most fitness landscapes have more than one dimension and therefore a 'jump' could include any number between 1 and N, where N is the dimensionality of the landscape. The Drift Rate setting —which may well be poorly named— controls the odds that a jump includes an additional dimension. All jumps must be at least one-dimensional, but 25 percent of them (on average) will include another dimension. 25% of those will include a third dimension and 25 percent of those a fourth and so on and so forth until the dimensionality of the landscape has been reached. Here's a list for 1000 jumps:

Drift Rate:    25%      

1D jumps:    750        

2D jumps:    187    

3D jumps:     47      

4D jumps:     12        

5D jumps:       3         

6D jumps:       1         

A good question to ask would be; "Why would you want a jump to include more than one dimension?" and the answer is that the more genes are related, the higher the changes that a multi-dimensional jump will yield an improvement. It's not difficult to imagine that you cannot improve your current state by only modifying a single gene. Sometimes you need to change two in unison in order to reach a better solution. If your genes are highly related (which is bad practice to begin with) then you may need to adjust the Drift Rate to a higher value.

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David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Site Dead on April 17, 2012 at 11:46am

Hello David,

WOW..like everyone just knows that?

thank you for the explanation, I have better understanding now and I will make sure genes are not highly related I had a few that way "just testing" (oops) I think the name is fine I just did not know its relationship to Fitness.

thanks again.

Wade

Permalink Reply by David Rutten on April 17, 2012 at 12:41pm

No, probably nobody just knew that.

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David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Site Dead on April 17, 2012 at 3:06pm

David,

Thanks again for taking the time. actually I'm glad I asked the question now.