'RobustTerminaton' object has no attribute 'n_max_gen'

[KyleYoung1997]

Hi when attempting to follow along the example to introduce objective space tolerance termination i.e.

termination = RobustTermination( MultiObjectiveSpaceTermination(tol=0.005, n_skip=5), period=20)

I am getting the following error:

if algorithm.termination.n_max_gen == algorithm.n_gen:
AttributeError: 'RobustTermination' object has no attribute 'n_max_gen'

I attempted to set this when initialising both MultiObjectiveSpaceTermination and RobustTermination as well as inspecting both classes (and DeltaToleranceTermination) but it doesn't appear as if there is any class variable for n_max_gen.

Any guidance here would be appreciated!

Cheers

[blankjul]

Can you provide an example where this code fails?

from pymoo.algorithms.moo.nsga2 import NSGA2
from pymoo.optimize import minimize
from pymoo.problems import get_problem
from pymoo.termination.ftol import MultiObjectiveSpaceTermination
from pymoo.termination.robust import RobustTermination
from pymoo.visualization.scatter import Scatter

problem = get_problem("zdt1")

algorithm = NSGA2(pop_size=100)

termination = RobustTermination(MultiObjectiveSpaceTermination(tol=0.005, n_skip=5), period=20)

res = minimize(problem,
               algorithm,
               termination=termination,
               seed=1,
               verbose=False)

plot = Scatter()
plot.add(problem.pareto_front(), plot_type="line", color="black", alpha=0.7)
plot.add(res.F, facecolor="none", edgecolor="red")
plot.show()

Seems to run without any issue for me.

[oli-hall]

@KyleYoung1997 I also came across this same issue. As the discussion here highlights, the documentation for this Termination appears to be out of date. However, what you can do to get a max generations termination in there as well, is to use a TerminateIfAny to combine the two termination conditions:

from pymoo.core.termination import TerminateIfAny
from pymoo.termination import get_termination
from pymoo.termination.ftol import MultiObjectiveSpaceTermination
from pymoo.termination.robust import RobustTermination

termination = TerminateIfAny(
    RobustTermination(
        MultiObjectiveSpaceTermination(tol=0.005, n_skip=5), 
        period=20
    ),
    get_termination("n_gen", 200)
)

[blankjul]

Ahh yes now I understand what is going wrong even without a code sample. Yes the code snipped above is the correct one. @oli-hall can you send me the link where the documentation needs to be updated?

[oli-hall]

Sure thing @blankjul – I got the tip about the documentation being out of date from this discussion – the documentation page itself is here – the main page that looks at Termination, in particular the section called 'Objective Space Tolerance'. Thanks!

[KyleYoung1997]

Apologies for the delayed response @blankjul. The fix from @oli-hall works perfectly. Thank you for the assistance.