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Description
Consider the following code to model the maximum independent set problem to solve the maximum clique using MIP and NetworkX:
import mip
import networkx
n = 2 ** 3
g = networkx.binomial_tree(n)
networkx.add_star(g, [i for i in range(n)])
g1 = networkx.complement(g)
model = mip.Model("Independent Set")
x = [model.add_var(var_type=mip.BINARY) for _ in range(len(g1.nodes))]
model.objective = mip.maximize(mip.xsum(x[i] for i in range(len(g1.nodes))))
for (i, j) in g1.edges:
model += x[i] + x[j] <= 1
model.optimize()
selected = [i for i in range(len(g1.nodes)) if x[i].x >= 0.99]
print(selected)
g2 = g.subgraph(selected)
If I try to access the model
variables in the watch
section, it gives he following message on terminal:
Information not available, model was not optimized yet.
And then, the debugger dies. I believe this is not what should happen, some help with this?