Method test_cv_explicit_fold_indices_labels

tests/python/test_basic.py:241–282

(self)

        assert len(cv) == (4)

    def test_cv_explicit_fold_indices_labels(self):
        params = {"max_depth": 2, "eta": 1, "objective": "reg:squarederror"}
        N = 100
        F = 3
        dm = xgb.DMatrix(data=np.random.randn(N, F), label=np.arange(N))
        folds = [
            # Train        Test
            ([1, 3], [5, 8]),
            ([7, 9], [23, 43, 11]),
        ]

        # Use callback to log the test labels in each fold
        class Callback(xgb.callback.TrainingCallback):
            def __init__(self) -> None:
                super().__init__()

            def after_iteration(
                self,
                model,
                epoch: int,
                evals_log: xgb.callback.TrainingCallback.EvalsLog,
            ):
                print([fold.dtest.get_label() for fold in model.cvfolds])

        cb = Callback()

        # Run cross validation and capture standard out to test callback result
        with tm.captured_output() as (out, err):
            xgb.cv(
                params,
                dm,
                num_boost_round=1,
                folds=folds,
                callbacks=[cb],
                as_pandas=False,
            )
            output = out.getvalue().strip()
        solution = (
            "[array([5., 8.], dtype=float32), array([23., 43., 11.],"
            + " dtype=float32)]"
        )
        assert output == solution


class TestBasicPathLike: