How can I optimize initial guess of a solution?

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Elia Paini 2021-5-13

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https://ww2.mathworks.cn/matlabcentral/answers/829038-how-can-i-optimize-initial-guess-of-a-solution

评论： Elia Paini 2021-5-19

Hi, I solved a system of non linear ODEs with bvp4c. The system is a bit complicated, since it contains 17 equations with 17 variables. I realized that initial guess strongly influences the final solution, which is normal. I tried to enter optimal values of my variables as initial guess, giving them the order of magnitude I expect during simulation. In this way, the maximum residual has decreased a lot, however it seems still high.

I have the following warning: ... The maximum residual is 0.16, while requested accuracy is 0.001

How can I further decrease the residue? Is there available an optimizer of initial guess?

Thank you!

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J. Alex Lee 2021-5-18

sorry, i don't have any suggestions. I am starting to use bvp4c/5c for my work as well, and it seems very random how well a solution is achieved...there is no way to control how the solver internally decides its itertions as far as i know...i even tried continuation, but bizarrely sometimes a solution will be very messed up, but then the next step in the continuation will be fine. i don't think these are very mature or well-developed tools...

Elia Paini 2021-5-19