Rename lazy layer to deferred (_DeferredDataModel / _deferred.py)

Per review, "lazy" was too generic and "host" would be wrong (cuDF inputs pass
through and stay on device). "Deferred" names the actual mechanism -- the
device build is deferred to solve, for host and device inputs alike -- and
avoids colliding with the Cython "wrapper". Pure rename: _lazy.py ->
_deferred.py, _LazyDataModel -> _DeferredDataModel, test_lazy.py ->
test_deferred.py. No behavior change.

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/_lazy.py python/cuopt/cuopt/routing/_deferred.pypython/cuopt/cuopt/routing/_lazy.py renamed to python/cuopt/cuopt/routing/_deferred.py

@@ -1,7 +1,7 @@
 # SPDX-FileCopyrightText: Copyright (c) 2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 # SPDX-License-Identifier: Apache-2.0
 
-"""Store-then-build (lazy) layer for the routing DataModel.
+"""Store-then-build (deferred build) layer for the routing DataModel.
 
 The public DataModel records its setter calls on the host and builds the device
 (Cython) model only transiently -- at solve, or when a getter is queried -- by
@@ -19,7 +19,7 @@
   * **Zero-CUDA construction.** The setter/getter surface is declared explicitly
     below rather than introspected from the compiled wrapper, so constructing and
     serializing a problem imports no CUDA/cuDF -- the wrapper is imported lazily
-    only when a device build actually happens. ``test_lazy`` fails if this
+    only when a device build actually happens. ``test_deferred`` fails if this
     declared surface drifts from the wrapper.
 
 Adding a new setter/getter to the DataModel:
@@ -30,7 +30,7 @@
      docstring -- forwarding to ``super()``.
   3. Add its name to ``_SETTERS`` (a mutator) or ``_GETTERS`` (a query) below.
 
-``test_lazy`` cross-checks these names against the wrapper's surface, so a
+``test_deferred`` cross-checks these names against the wrapper's surface, so a
 missing entry fails CI rather than silently dropping the call's data.
 """
 
@@ -136,7 +136,7 @@ def _normalize(x):
     return x
 
 
-class _LazyDataModel:
+class _DeferredDataModel:
     """Records DataModel setter calls; builds the device model transiently."""
 
     def __init__(self, num_locations, fleet_size, n_orders=-1):
@@ -207,11 +207,11 @@ def _install_methods():
         if _methods_installed:
             return
         for name in _SETTERS:
-            if name not in _LazyDataModel.__dict__:
-                setattr(_LazyDataModel, name, _make_setter(name))
+            if name not in _DeferredDataModel.__dict__:
+                setattr(_DeferredDataModel, name, _make_setter(name))
         for name in _GETTERS:
-            if name not in _LazyDataModel.__dict__:
-                setattr(_LazyDataModel, name, _make_getter(name))
+            if name not in _DeferredDataModel.__dict__:
+                setattr(_DeferredDataModel, name, _make_getter(name))
         _methods_installed = True
 
 

python/cuopt/cuopt/routing/vehicle_routing.py

@@ -7,7 +7,7 @@
 
 from cuopt import routing
 from cuopt.routing import vehicle_routing_wrapper
-from cuopt.routing._lazy import _LazyDataModel
+from cuopt.routing._deferred import _DeferredDataModel
 from cuopt.utilities import catch_cuopt_exception
 
 from .validation import (
@@ -20,7 +20,7 @@
 )
 
 
-class DataModel(_LazyDataModel):
+class DataModel(_DeferredDataModel):
     """
 
     DataModel(n_locations, n_fleet, n_orders: int = -1)

…n/cuopt/cuopt/tests/routing/test_lazy.py …opt/cuopt/tests/routing/test_deferred.pypython/cuopt/cuopt/tests/routing/test_lazy.py renamed to python/cuopt/cuopt/tests/routing/test_deferred.py python/cuopt/cuopt/tests/routing/test_lazy.py renamed to python/cuopt/cuopt/tests/routing/test_deferred.py

@@ -5,10 +5,10 @@
 
 from cuopt import routing
 from cuopt.routing import vehicle_routing_wrapper
-from cuopt.routing._lazy import _SKIP_GETTERS
+from cuopt.routing._deferred import _SKIP_GETTERS
 
 
-def test_lazy_covers_wrapper_surface():
+def test_deferred_covers_wrapper_surface():
     """Every public wrapper DataModel method must be handled by the recording
     layer (installed as a recorder/getter or an explicit override). This fails
     loudly if a new wrapper method -- e.g. a mutator not named set_*/add_* --
@@ -24,7 +24,7 @@ def test_lazy_covers_wrapper_surface():
         and name not in handled
     ]
     assert not missing, (
-        f"lazy build layer does not handle wrapper methods {missing}; "
+        f"deferred-build layer does not handle wrapper methods {missing}; "
         "add a recorder/getter or list them in _SKIP_GETTERS"
     )