Galapagos with Diva, Can I limit the population number to 30 instead of 50? will the results be accurate?

Hi everyone, I just used Galapagos with Diva to test 162 different configurations, I used the default settings in Galapagos, , I started running the solver 36 hours ago, it performed 600 simulations, and it is currently working on the 11th generation, it is still running I haven't stopped it yet. I'm going to use the solver again to test 1296 configurations will limiting the population to 30 affect the results accuracy, and will it make the solver finish in less time?

Another question I have, If I'm testing only 162 configurations ( I have 5 sliders 2x3x3x3x3= 162), then how come Galapagos tested 600 solutions with many repeated configurations, and surprisingly, it is still running? am I missing something.

One last question, I heard about Genopt to use for Genetic algorithm, I also heard it is a better way to test large numbers of simulations, However I have no idea how to use, does anyone know if it is a plug-in for Grasshopper, or stand-alone application ?

Replies to This Discussion

Permalink Reply by David Rutten on April 28, 2014 at 12:59pm

First thing to realise is that Galapagos is not a good tool for doing brute force searches. The algorithms it uses are specifically designed to be different than brute force search.

The population size for the evolutionary solver is only important if your fitness landscape has lots of detail. Smooth landscapes can be solved with small population sizes (say, 5 x the number of genes).

Galapagos will attempt to not solve the same genome twice. When it happens to generate a genome it solved before, it will apply a number of mutations until it finds a new genome or until it has pointlessly tried more than a few dozen times to find a new genome. So if you only have a limited number of possible genomes, after a while Galapagos will no longer compute any new information. At this point you're basically just wasting your time.

If you want to do a brute force search, a custom script will be a better solution I think.

David Rutten

david@mcneel.com

Permalink Reply by Ninja on April 28, 2014 at 1:25pm

David, Thanks for your response, I just did a quick search of Brute force(I'm ashamed to say I've never heard of it ) , and I think that's what I want exactly. I don't know how to write a custom script, but I have a plug-in in Galapagos called TT ToolBox and it has a brute force component, can anyone provide their feedback about the use of this component with Diva simulations. Or can anyone provide me detailed instruction of how to write a script for my little project. Thanks

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