Drop cudf.Series default-arg change; namespace move alone is enough

With the dataset/batch helpers no longer re-exported from cuopt.routing,
importing the package never touches utils / utils_wrapper, so it is GPU-free
without the None-sentinel change to generate_dataset. Revert utils.py and
utils_wrapper.pyx to keep the diff focused on the namespace move, and drop the
utils-imports-without-a-gpu test. The test that importing cuopt.routing does
not require a GPU is kept.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Ramakrishna Prabhu <ramakrishnap@nvidia.com>

Author: ramakrishnap-nv

python/cuopt/cuopt/routing/utils.py

@@ -1,4 +1,4 @@
-# SPDX-FileCopyrightText: Copyright (c) 2021-2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-FileCopyrightText: Copyright (c) 2021-2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 # SPDX-License-Identifier: Apache-2.0
 
 import glob
@@ -17,10 +17,10 @@
 def generate_dataset(
     locations=100,
     asymmetric=True,
-    min_demand=None,
-    max_demand=None,
-    min_capacities=None,
-    max_capacities=None,
+    min_demand=cudf.Series(),
+    max_demand=cudf.Series(),
+    min_capacities=cudf.Series(),
+    max_capacities=cudf.Series(),
     min_service_time=0,
     max_service_time=0,
     tw_tightness=0.0,
@@ -114,18 +114,6 @@ def generate_dataset(
         Time windows and multi dimension
         capacity for each vehicle.
     """
-    # Default to empty device series here rather than in the signature:
-    # a cudf.Series() default is constructed at import time and needs a GPU,
-    # which would make importing this module fail on a GPU-less host.
-    if min_demand is None:
-        min_demand = cudf.Series()
-    if max_demand is None:
-        max_demand = cudf.Series()
-    if min_capacities is None:
-        min_capacities = cudf.Series()
-    if max_capacities is None:
-        max_capacities = cudf.Series()
-
     if (
         min_demand.shape[0] != max_demand.shape[0]
         or max_demand.shape[0] != min_capacities.shape[0]

python/cuopt/cuopt/routing/utils_wrapper.pyx

@@ -1,4 +1,4 @@
-# SPDX-FileCopyrightText: Copyright (c) 2021-2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-FileCopyrightText: Copyright (c) 2021-2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved. # noqa
 # SPDX-License-Identifier: Apache-2.0
 
 
@@ -35,27 +35,15 @@ class DatasetDistribution(IntEnum):
     RANDOM_CLUSTERED = dataset_distribution_t.RANDOM_CLUSTERED
 
 
-def generate_dataset(locations=100, asymmetric=True, min_demand=None,
-                     max_demand=None, min_capacities=None,
-                     max_capacities=None, min_service_time=0,
+def generate_dataset(locations=100, asymmetric=True, min_demand=cudf.Series(),
+                     max_demand=cudf.Series(), min_capacities=cudf.Series(),
+                     max_capacities=cudf.Series(), min_service_time=0,
                      max_service_time=0, tw_tightness=0.0,
                      drop_return_trips=0.0, shifts=1,
                      n_vehicle_types=1, n_matrix_types=1,
                      distribution=DatasetDistribution.CLUSTERED,
                      center_box=None, seed=0):
 
-    # Default to empty device series here rather than in the signature:
-    # a cudf.Series() default is constructed at import time and needs a GPU,
-    # which would make importing this module fail on a GPU-less host.
-    if min_demand is None:
-        min_demand = cudf.Series()
-    if max_demand is None:
-        max_demand = cudf.Series()
-    if min_capacities is None:
-        min_capacities = cudf.Series()
-    if max_capacities is None:
-        max_capacities = cudf.Series()
-
     cdef unique_ptr[handle_t] handle_ptr
     handle_ptr.reset(new handle_t())
     handle_ = handle_ptr.get()

python/cuopt/cuopt/tests/routing/test_gpu_free_import.py

@@ -31,18 +31,3 @@ def test_routing_imports_without_a_gpu():
         "dm = r.DataModel(3, 2)\n"
         "dm.add_cost_matrix(np.eye(3, dtype=np.float32))\n"
     )
-
-
-def test_routing_utils_imports_without_a_gpu():
-    """cuopt.routing.utils must import on a GPU-less host too.
-
-    Its helpers build empty cudf.Series objects; doing so in a default argument
-    would run at import time and fail with cudaErrorNoDevice where no GPU is
-    visible. This guards that the construction stays in the function bodies, so
-    tests importing utils can be collected without a GPU.
-    """
-    _run_without_gpu(
-        "from cuopt.routing import utils\n"
-        "assert callable(utils.generate_dataset)\n"
-        "assert callable(utils.add_vehicle_constraints)\n"
-    )