[dask] Fix union of workers. (#6375)

2020-11-13 16:55:05 +08:00
parent fcfeb4959c
commit 4ccf92ea34
2 changed files with 21 additions and 1 deletions
--- a/python-package/xgboost/dask.py
+++ b/python-package/xgboost/dask.py
@@ -627,7 +627,7 @@ def _get_workers_from_data(dtrain: DaskDMatrix, evals=()):
            assert len(e) == 2
            assert isinstance(e[0], DaskDMatrix) and isinstance(e[1], str)
            worker_map = set(e[0].worker_map.keys())
-            X_worker_map.union(worker_map)
+            X_worker_map = X_worker_map.union(worker_map)
    return X_worker_map