Infinite loop when running isotonic regression with some zero-valued weights #4297
Description
I extract the following bug from the discussion in #2507 (comment) :
import numpy as np
import sklearn.isotonic
regression = sklearn.isotonic.IsotonicRegression()
n_samples = 60
x = np.linspace(-3, 3, n_samples)
y = x + np.random.uniform(size=n_samples)
w = np.random.uniform(size=n_samples)
w[5:8] = 0
regression.fit(x, y, sample_weight=w)
This bug alone should probably be considered a release critical bug for 0.16.