MATLAB Answers

Altering Default MaxFunEvals

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Alex
Alex on 2 Feb 2012
Edited: Gova ReDDy on 26 Sep 2013
Hi, I'm having trouble altering the default number of evaluations (300) of an fsolve. My .m file looks like this (function omitted):
function solveeqs()
guess=[1.6 0 300];
options = optimset('MaxFunEvals',1e10);
[result, fval, exit, output]=fsolve(@eqns, guess);
result
fval
eqns(guess)
exit
output
end
I thought that the options command might fix it, but the output defines the evaluation limit at 300 anyways. Any tips?

Answers (1)

Sean de Wolski
Sean de Wolski on 2 Feb 2012
You're not passing the options structure to fsolve()
options = optimset('MaxFunEvals',1e10);
[result, fval, exit, output]=fsolve(@eqns, guess,options);
Just make sure options is defined before you call fsolve.
  3 Comments
Alex
Alex on 2 Feb 2012
The equations it's working on are very complex non-linear differential equations, but I'll post the code below, line for line, with the output:
function solveeqs()
guess=[1.6 0 300];
options = optimset('MaxFunEvals',1e10);
[result, fval, exit, output]=fsolve(@eqns, guess, options);
result
fval
eqns(guess)
exit
output
end
function fcns=eqns(z)
n=z(1);
k=z(2);
d=z(3);
fcns(1)=((((1-(n-1i.*k))./(1+(n-1i.*k)))+(((n-1i.*k)-(1.694-1i.*3.666))./((n-1i.*k)+(1.694-1i.*3.666))).*(exp(1).^(-2.*1i.*(2.*pi./250).*(n-1i.*k).*d)))./(1+((1-(n-1i.*k))./(1+(n-1i.*k))).*(((n-1i.*k)-(1.694-1i.*3.666))./((n-1i.*k)+(1.694-1i.*3.666))).*(exp(1).^(-2.*1i.*(2.*pi./250).*(n-1i.*k).*d))))-.922269;
fcns(2)=((((1-(n-1i.*k))./(1+(n-1i.*k)))+(((n-1i.*k)-(1.7046-1i.*3.7066))./((n-1i.*k)+(1.7046-1i.*3.7066))).*(exp(1).^(-2.*1i.*(2.*pi./251).*(n-1i.*k).*d)))./(1+((1-(n-1i.*k))./(1+(n-1i.*k))).*(((n-1i.*k)-(1.7046-1i.*3.7066))./((n-1i.*k)+(1.7046-1i.*3.7066))).*(exp(1).^(-2.*1i.*(2.*pi./251).*(n-1i.*k).*d))))-.92401;
fcns(3)=((((1-(n-1i.*k))./(1+(n-1i.*k)))+(((n-1i.*k)-(1.7152-1i.*3.7472))./((n-1i.*k)+(1.7152-1i.*3.7472))).*(exp(1).^(-2.*1i.*(2.*pi./252).*(n-1i.*k).*d)))./(1+((1-(n-1i.*k))./(1+(n-1i.*k))).*(((n-1i.*k)-(1.7152-1i.*3.7472))./((n-1i.*k)+(1.7152-1i.*3.7472))).*(exp(1).^(-2.*1i.*(2.*pi./252).*(n-1i.*k).*d))))-.925751;
end
Outputs:
run eqnsr
Solver stopped prematurely.
fsolve stopped because it exceeded the iteration limit,
options.MaxIter = 400 (the default value).
result =
1.0e+002 *
1.3445 + 5.5767i 5.5777 - 1.3435i 3.7721 + 3.5028i
fval =
1.0e-003 *
0.0734 - 0.9412i -0.0454 - 0.0117i -0.1829 + 0.9172i
ans =
-1.7380 - 0.1528i -1.7283 - 0.2051i -1.7148 - 0.2567i
exit =
0
output =
iterations: 400
funcCount: 1580
algorithm: 'trust-region dogleg'
firstorderopt: 5.9222e-004
message: [1x127 char]
Since this is a test of it's functionality (I know what values it should be returning (approximately), I'm concerned that it just isn't getting close enough. A result of .0011 isn't as close to 0 as I would like.

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