Fmincon works for MATLAB version 2020a but not for version 2021b

Hello!

I have a convex function (i.e., energy) that I would like to minimize on a single variable named x. My code looks like this:

x    = optimvar('x', 'LowerBound', 0);  %Definition of the variable with constraints
prob = optimproblem;                    %Definition of the problem
prob.Objective = energyfun;             %Set the objective to minimize energy
x0.x = 10;                              % Initial point of the optimization variable
sol = solve(prob, x0);

I am getting the following error: Gradient at initial point contains Inf, NaN, or a complex values. Fmincon cannot continue.

But the most interesting part is that I have tried my code on different computers with MATLAB versions 2021b and 2020a. Basically, it works on the 2020a version but not on 2021b.

I have checked the optimoptions of the fmincon solver in both versions and they are exactly the same. Am I missing something or did something changed between these two versions?

Thank you all in advance!

[Mike Croucher]

Could you include all of your code please so we can try to run it

[Huseyin Eken]

Please find the script attached.

[Matt J]

It is strange to be using fmincon for a simple 1D minimization. You could use fminbnd, instead. Then you wouldn't need to worry about gradients, because fminbnd doesn't use them..

[Huseyin Eken]

Thanks for the input, i will try also with fminbnd as you suggested. Actually, I can solve the problem with other solvers like the genetic algorithm. What I found strange was that fmincon works for a version of MATLAB and not for the other.

As a side note, I would like to add more parameters to the optimization problem later on. This is just the starting point that I found in literature.

Answer 1

[Kumar Pallav]

Hi,

Please refer to a similar issue here.

You could set breakpoints for debugging at the command line:

dbstop if naninf

and run your program. If it stops in the debugger then you encountered a nan or inf and you will be able to explore the values in the debugger to see what is happening.