What are all the options to improve Fsolve?

Hi All

Using FSolve , to solve a set of non linear equations , I get warnings like :

optimization terminated : first order optimality is less than options.TolFun.

I added :

options = optimset('MaxFunEvals',1e20);

to use as options, is it enough ? too high ? too low ?

and what are all the options that I can deliver a precise solution ?

[Torsten]

The message you obtain is not a warning, but you are informed that the calculation has been successfully terminated.

[farzad]

Thank you very much

Exit Flag for both of the case that the results were desirable and for the case that they had error and not as expected

exitflag : 1

what does Output and fval say ?

how can I increase the solution precision ?

Answer 1

[Matt J]

The complete list of fsolve options is given here

https://www.mathworks.com/help/optim/ug/fsolve.html#buta__s-options

Generally, speaking, they are tweak parameters, i.e., the best values of these parameters will be problem specific. You should, in any case, check the exitflag output,

[x,fval,exitflag,output] = fsolve(___)

to interpret why fsolve stopped, and if it thinks it was successful.

[farzad]

Thank you very much

where do I use this line ? during the solution ? or after the solution is finished ?

Exit Flag for both of the case that the results were desirable and for the case that they had error and not as expected

exitflag : 1

what does Output and fval say ?

how can I increase the solution precision ?

[farzad]

Also I used

optimset

but in the help I see

optimoptions

and second : if I have to assign multiple options, like 'MaxFunEvals' ; checkgradients, tolerances etc

how do I do that?

[farzad]

Also

I use MATLAB 2007 , it seems many of the options bug me with the error

too many input arguments

[farzad]

Still looking forward

[Matt J]

Documentation for older versions of Matlab can be found here

https://www.mathworks.com/help/doc-archives.html

You need to consult the R2007 documentation page for fsolve to read about the options avaialble and their meanings. Optimoptions replaced/deprecated optimset in later versions of Matlab. Both allow you to set multiple option parameters in the same call, however. The page for optimset in R2007a, lists this as the first syntax

https://www.mathworks.com/help/releases/R2007a/techdoc/index.html?/help/releases/R2007a/techdoc/ref/optimset.html&https://www.mathworks.com/search/site_search.html?q=optimset&searchArrow.x=0&searchArrow.y=0&c%5B%5D=r2007a