@ignore_warnings
def test_warm_start():
    # A 1-iteration second fit on same data should give almost same result
    # with warm starting, and quite different result without warm starting.
    # Warm starting does not work with liblinear solver.
    X, y = iris.data, iris.target

    solvers = ['newton-cg', 'sag']
    # old scipy doesn't have maxiter
    if sp_version >= (0, 12):
        solvers.append('lbfgs')

    for warm_start in [True, False]:
        for fit_intercept in [True, False]:
            for solver in solvers:
                for multi_class in ['ovr', 'multinomial']:
                    clf = LogisticRegression(tol=1e-4, multi_class=multi_class,
                                             warm_start=warm_start,
                                             solver=solver,
                                             random_state=42, max_iter=100,
                                             fit_intercept=fit_intercept)
                    clf.fit(X, y)
                    coef_1 = clf.coef_

                    clf.max_iter = 1
                    with ignore_warnings():
                        clf.fit(X, y)
                    cum_diff = np.sum(np.abs(coef_1 - clf.coef_))
                    msg = ("Warm starting issue with %s solver in %s mode "
                           "with fit_intercept=%s and warm_start=%s"
                           % (solver, multi_class, str(fit_intercept),
                              str(warm_start)))
                    if warm_start:
                        assert_greater(2.0, cum_diff, msg)
                    else:
                        assert_greater(cum_diff, 2.0, msg)
dataset/ETHPy150Open scikit-learn/scikit-learn/sklearn/linear_model/tests/test_logistic.py/test_warm_start/original