Fminunc Stopping Critera beyond StepTol and FunTol

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Lorcan Conlon 2020-9-15

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594352-fminunc-stopping-critera-beyond-steptol-and-funtol

I have a function whos input is a 83 element vector and whos output is a 8x8 matrix. I am tryin to use fminunc to get my output matrix as close as possible to a target matrix which is just a random 8x8 unitary matrix. fminunc is already getting me very close to the desired matrix with the following code:

fun = @(x) sum(sum(abs(Urand-UT([x]))));

x0=randn(83,1);

options = optimoptions('fminunc','Display','Iter','FunctionTolerance',1e-30,'StepTolerance',1e-30,'MaxFunctionEvaluations',1e9,'MaxIter',1e9,'OptimalityTolerance',1e-30);

[x,fval] = fminunc(fun,x0,options);

This generates the target matrix to within 1e-5. However i want to know how I can get even closer. The stop message is

"fminunc stopped because it cannot decrease the objective function along the current search direction."

I assume there is some way which I can make the solver take smaller steps so that the function might decrease just a little bit more. However Ido not know how to do this beyond what i have done in setting the tolerances. Can anyone help with this?