stopping criteria for particle swarm optimization algorithm

Hello everyone,

I am running an optimization problem using particle swarm algorithm pso). However, i have a problem related to the stopping criteria.

In fact, as i understood, pso will stop when 1) maximum iterations are reached or 2)in the last MaxStalliterations is less than function tolerance. Does my understanding seem correct ?

Indeed, in my optimization problem, the plot of the objective function shows that at iteration 11, the optimal objective function value is reached. Since, all parameters in pso are left by default, i expect that the algorithm will stop at iteration 31 following the second criteria (By defaut, MaxStalliterations is equal to 20). However, it does not stop.

Could you tell me why please ?

Here a plot of the objective function in function of number of iterations.

Thank you in advance,

Best Regards,