Optimization toolbox: "lsqnonlin" stopped because it exceeded the function evaluation limit

Hi everyone,

I am using the lsqnonlin from optimization toolbox for a problem. After 88 itterations I am getting my answeres and this msg:

lsqnonlin stopped because it exceeded the function evaluation limit

options.MaxFunEvals=800

As I am not satisfied with the answeres, I am guessing maybe changing the MaxFunEvals to a higher number can help. Could anyone let me know how I can set it in the toolbox? I am not seeing any parameter like this in the options.

Thank you

[Walter Roberson]

https://www.mathworks.com/help/optim/ug/current-and-legacy-option-name-tables.html

old name MaxFunEvals

current name MaxFunctionEvaluations

The name to use depends upon which options constructing routine you are using

Answer 1

[John D'Errico]

Note that I don't know which release of MATLAB you are using. But what did you try? This seems clear:

opts = optimoptions('lsqnonlin')
opts = 
  lsqnonlin options:

   Options used by current Algorithm ('trust-region-reflective'):
   (Other available algorithms: 'levenberg-marquardt')

   Set properties:
     No options set.

   Default properties:
                   Algorithm: 'trust-region-reflective'
              CheckGradients: 0
                     Display: 'final'
    FiniteDifferenceStepSize: 'sqrt(eps)'
        FiniteDifferenceType: 'forward'
           FunctionTolerance: 1e-06
         JacobianMultiplyFcn: []
      MaxFunctionEvaluations: '100*numberOfVariables'
               MaxIterations: 400
         OptimalityTolerance: 1e-06
                   OutputFcn: []
                     PlotFcn: []
    SpecifyObjectiveGradient: 0
               StepTolerance: 1e-06
         SubproblemAlgorithm: 'factorization'
                    TypicalX: 'ones(numberOfVariables,1)'
                 UseParallel: 0

Now, nothing stops you from setting:

opts.MaxFunctionEvaluations = 2000
opts = 
  lsqnonlin options:

   Options used by current Algorithm ('trust-region-reflective'):
   (Other available algorithms: 'levenberg-marquardt')

   Set properties:
      MaxFunctionEvaluations: 2000
   Default properties:
                   Algorithm: 'trust-region-reflective'
              CheckGradients: 0
                     Display: 'final'
    FiniteDifferenceStepSize: 'sqrt(eps)'
        FiniteDifferenceType: 'forward'
           FunctionTolerance: 1e-06
         JacobianMultiplyFcn: []
               MaxIterations: 400
         OptimalityTolerance: 1e-06
                   OutputFcn: []
                     PlotFcn: []
    SpecifyObjectiveGradient: 0
               StepTolerance: 1e-06
         SubproblemAlgorithm: 'factorization'
                    TypicalX: 'ones(numberOfVariables,1)'
                 UseParallel: 0

As you can see, opts now contains the desired value. Pass opts into lsqnonlin to use these settings.

As Walter points out, in older releases, the property name was MaxFunEvals. But the same sort of thing will still apply. You may just need to use the proper property name.

Having said that, frequently when you run out of function evals or iterations, it means your problem is not converging very well. Tht in turn either means that your starting values are particularly poor, or that your problem is fairly ill-posed. In either case, merely increasing the function evals will not really help that much. Essentially, it says that you really need to get better data or a better model or better starting values, each a far better choice than merely increasing the function evals allowed.

[Mohammad Heidari]

Thank you for the useful guidance. This really helped.

[has azz]

Hi John could you please let me know in which line i can introduce these corrections in my code. thanks