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What should I do if Fsolve can not find a solution in the middle of the solution ?

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farzad
farzad on 19 Jun 2019
Commented: Matt J on 21 Jun 2019
Hi All
despite having defined a very tight tolerance and high MaxnoEvals and iteration , I get Fsolve Stalled. I don't know how to follow to use fminunc to find the local minimum possible
options = optimset('Display','iter','MaxFunEvals',1e8,'MaxIter',1e20,'TolFun',1e-15,'DerivativeCheck','on','Diagnostics','on');
Norm of First-order Trust-region
Iteration Func-count f(x) step optimality radius
0 10 8.03914e+08 1.29e+07 1
1 20 7.75287e+08 1 1.26e+07 1
2 30 7.06551e+08 2.5 1.18e+07 2.5
3 40 5.51576e+08 6.25 9.92e+06 6.25
4 50 2.58383e+08 15.625 6.03e+06 15.6
5 60 7.16959e+06 39.0625 6.8e+05 39.1
6 70 22001.2 9.27933 3.08e+04 97.7
7 80 0.428073 0.565927 118 97.7
8 90 3.18478e-10 0.00322117 0.00386 97.7
9 100 2.03486e-22 9.70831e-08 5.31e-09 97.7
10 110 1.62955e-22 4.45752e-14 5.46e-09 97.7
Equation solved, fsolve stalled.
fsolve stopped because the relative size of the current step is less than the
default value of the step size tolerance squared and the vector of function values
is near zero as measured by the selected value of the function tolerance.
<stopping criteria details>
the error :
Diagnostic Information
Number of variables: 9
Functions
Objective: root2d
Gradient: finite-differencing
Algorithm selected
trust-region-dogleg
____________________________________________________________
End diagnostic information
Error using trustnleqn (line 28)
Objective function is returning undefined values at initial point. FSOLVE cannot continue.
Error in fsolve (line 388)
trustnleqn(funfcn,x,verbosity,gradflag,options,defaultopt,f,JAC,...
Error in Fsolver (line 91)
[x,fval,exitflag,output] = fsolve(fun,x0,options);

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Accepted Answer

Matt J
Matt J on 19 Jun 2019
Edited: Matt J on 19 Jun 2019
Look what it says: Equation solved!
Isn't that great?

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farzad
farzad on 21 Jun 2019
what do you mean by get it working ?
shouldn't I use fmin instead of fsolve to find local minimum ?

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