Error in plotting pareto front using pyomo in python

Question

I am trying to plot the pareto front for a simplified version of my multi-objective optimization problem (trying to figure out how everything works). I am completely new to this and cannot figure out what the error I am getting means:

TypeError: '>' not supported between instances of 'generator' and 'int'

I am using an existing code for the plotting, so I'm pretty sure the error is in how I formulated the problem, but I'm not sure what it is. This is my code:

v=[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
w=[22.0, 31.0, 0.0, 0.0, 11416.0, 0.0, 0.0, 0.0, 0.0, 15376.6, 977.97, 4324.97, 3264.79, 32.4, 43.02, 0.029, 0.2,0.00185, 0.00185, 0.0001, 0.03, 0.017, 0.0,0,0,0,0,0,0]
e=[562.51, 562.51, 0.0, 0.0, 223.16, 0.0, 0.0, 0.0, 0.0, 1401.63, 411.42, 1401.63, 0.0,312.53, 17195.71, 0.623, 15.14,0.01, 4.5, 23.42, 0.66,0,0,0,0,0,0,0,0]
g=[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 840.000,469.000,46.000,18.000,4.000,12.000,0,0,0,0]
        
class WEN(Problem):

    def __init__(self):
        super().__init__(n_var=v, n_obj=2, n_ieq_constr=2, xl=np.array(0 for i in range(29)), xu=None)

    def _evaluate(self, x, out, *args, **kwargs):
        f1=[numpy.dot(v,e)]
        f2=[numpy.dot(v,w)]
        g1=[(numpy.dot(v*w)/100)-585]
        g2=[(numpy.dot(v*g)*0.00001)-1610]
        out["F"] = [f1, f2]
        out["G"] = [g1, g2]
        
from pymoo.visualization.scatter import Scatter
from pymoo.algorithms.moo.nsga2 import RankAndCrowdingSurvival
from pymoo.core.mixed import MixedVariableGA
from pymoo.optimize import minimize

problem = WEN()

algorithm = MixedVariableGA(pop_size=20, survival=RankAndCrowdingSurvival())

res = minimize(problem,
               algorithm,
               ('n_gen', 50),
               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()

Any help, tips, advice (on any aspect of Python coding and/or optimization in Python) would be greatly appreciated.

The code you posted doesn't look like standard Pyomo code. Could you modify your question to include a minimal working example and the full error message (including the line throwing the error)? — Bethany Nicholson, Aug 29 '22 at 16:01
Looks like you used the wrong tag for your question. You used the "pyomo" tag instead of "pymoo" — Bethany Nicholson, Aug 29 '22 at 22:38

score 0 · Answer 1 · answered Aug 29 '22 at 19:30

In case, anyone was having the same problem, the error was because I put in a list for the n_var argument in the init function of the class, instead of the length of the list (or an integer value). So the proper code for that line would be:

class WEN(Problem):

    def __init__(self):
        super().__init__(n_var=len(v), n_obj=2, n_ieq_constr=2, xl=0.0, xu=None)

The rest of the code does not work however, because I was trying to impose and existing code for plotting on a problem with different dimensions, so I'll try to figure that part out next.

Error in plotting pareto front using pyomo in python

1 Answers1