pylibcugraph: declare cupy and numpy hard dependencies (#4854)

While testing stuff for #4804, I found that `pylibcugraph` has a hard runtime dependency on `cupy` and `numpy`, but isn't declaring them
 
```shell
docker run \
    --rm \
    --gpus 0 \
    -it rapidsai/ci-wheel:latest \
    bash

python -m pip install 'pylibcugraph-cu12==25.2.*,>=0.0.0a0'
python -c "import pylibcugraph"
```

```text
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/pyenv/versions/3.12.7/lib/python3.12/site-packages/pylibcugraph/__init__.py", line 18, in <module>
    from pylibcugraph.graphs import SGGraph, MGGraph
  File "graphs.pyx", line 1, in init pylibcugraph.graphs
  File "utils.pyx", line 20, in init pylibcugraph.utils
ModuleNotFoundError: No module named 'cupy'
```

This declares those dependencies.

It also promotes `cugraph-service-server`'s `numpy` dependency to a hard runtime dependency.

## Notes for Reviewers

### Evidence that `pylibcugraph` *already* has a hard dependency on these libraries

They're used unconditionally here:

https://github.com/rapidsai/cugraph/blob/cddd69ea3f62cabdb3aa2b7b6676e0b74ab4eefc/python/pylibcugraph/pylibcugraph/utils.pyx#L19-L20

But have import guards in other places:

https://github.com/rapidsai/cugraph/blob/cddd69ea3f62cabdb3aa2b7b6676e0b74ab4eefc/python/pylibcugraph/pylibcugraph/sssp.pyx#L127-L139

So this PR doesn't introduce new hard dependencies... it just makes them explicit, to make it easier to install and run `pylibcugraph`.

### How was this not caught in CI?

Import tests aren't run here for conda packages, because conda builds happen on CPU-only nodes.

https://github.com/rapidsai/cugraph/blob/cddd69ea3f62cabdb3aa2b7b6676e0b74ab4eefc/ci/build_python.sh#L27-L30

And `numpy` and `cupy` are probably getting pulled in by some of the wheels' test dependencies, like `cudf`, here:

https://github.com/rapidsai/cugraph/blob/cddd69ea3f62cabdb3aa2b7b6676e0b74ab4eefc/ci/test_wheel.sh#L17

### Should we just make the other unconditional cases conditional with try-catching?

No. Talked with @rlratzel, @ChuckHastings, and @eriknw offline, and we agreed to declare these as hard runtime dependencies (and remove the try-catching in places that had it).

Authors:
  - James Lamb (https://github.com/jameslamb)

Approvers:
  - Rick Ratzel (https://github.com/rlratzel)
  - Bradley Dice (https://github.com/bdice)

URL: #4854

conda/recipes/pylibcugraph/meta.yaml

@@ -1,4 +1,4 @@
-# Copyright (c) 2023-2024, NVIDIA CORPORATION.
+# Copyright (c) 2023-2025, NVIDIA CORPORATION.
 
 {% set version = environ['RAPIDS_PACKAGE_VERSION'].lstrip('v') + environ.get('VERSION_SUFFIX', '') %}
 {% set minor_version = version.split('.')[0] + '.' + version.split('.')[1] %}
@@ -74,7 +74,9 @@ requirements:
     {% else %}
     - cuda-cudart
     {% endif %}
+    - cupy >=12.0.0
     - libcugraph ={{ version }}
+    - numpy>=1.23,<3.0a0
     - pylibraft ={{ minor_version }}
     - python
     - rmm ={{ minor_version }}

dependencies.yaml

@@ -141,8 +141,10 @@ files:
       table: project
     includes:
       - cuda_wheels
+      - depends_on_cupy
       - depends_on_pylibraft
       - depends_on_rmm
+      - python_run_pylibcugraph
   py_test_pylibcugraph:
     output: pyproject
     pyproject_dir: python/pylibcugraph
@@ -199,7 +201,7 @@ files:
       key: test
     includes:
       - test_python_common
-      - test_python_cugraph
+      - test_python_cugraph_service_server
 channels:
   - rapidsai
   - rapidsai-nightly
@@ -421,6 +423,11 @@ dependencies:
           - matrix: # All CUDA 11 versions
             packages:
               - cuda-python>=11.8.5,<12.0a0
+  python_run_pylibcugraph:
+    common:
+      - output_types: [conda, pyproject, requirements]
+        packages:
+          - *numpy
   python_run_cugraph_service_client:
     common:
       - output_types: [conda, pyproject]
@@ -468,6 +475,11 @@ dependencies:
       - output_types: [conda]
         packages:
           - *thrift
+  test_python_cugraph_service_server:
+    common:
+      - output_types: [conda, pyproject]
+        packages:
+          - *numpy
   test_python_pylibcugraph:
     common:
       - output_types: [conda, pyproject]

python/cugraph-service/server/pyproject.toml

@@ -46,16 +46,12 @@ cugraph-service-server = "cugraph_service_server.__main__:main"
 
 [project.optional-dependencies]
 test = [
-    "certifi",
-    "networkx>=2.5.1",
     "numpy>=1.23,<3.0a0",
     "pandas",
     "pytest",
     "pytest-benchmark",
     "pytest-cov",
     "pytest-xdist",
-    "python-louvain",
-    "scikit-learn>=0.23.1",
     "scipy",
 ] # This list was generated by `rapids-dependency-file-generator`. To make changes, edit ../../../dependencies.yaml and run `rapids-dependency-file-generator`.
 

python/pylibcugraph/pylibcugraph/bfs.pyx

@@ -1,4 +1,4 @@
-# Copyright (c) 2022-2024, NVIDIA CORPORATION.
+# Copyright (c) 2022-2025, NVIDIA CORPORATION.
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
@@ -14,6 +14,8 @@
 # Have cython use python 3 syntax
 # cython: language_level = 3
 
+import cupy
+
 from libc.stdint cimport uintptr_t
 from libc.stdint cimport int32_t
 from libc.limits cimport INT_MAX
@@ -141,11 +143,6 @@ def bfs(ResourceHandle handle, _GPUGraph graph,
     >>> })
     """
 
-    try:
-        import cupy
-    except ModuleNotFoundError:
-        raise RuntimeError("bfs requires the cupy package, which could not "
-                           "be imported")
     assert_CAI_type(sources, "sources")
 
     if depth_limit <= 0:

python/pylibcugraph/pylibcugraph/node2vec.pyx

@@ -1,4 +1,4 @@
-# Copyright (c) 2022-2024, NVIDIA CORPORATION.
+# Copyright (c) 2022-2025, NVIDIA CORPORATION.
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
@@ -14,6 +14,8 @@
 # Have cython use python 3 syntax
 # cython: language_level = 3
 
+import cupy
+
 from libc.stdint cimport uintptr_t
 
 from pylibcugraph._cugraph_c.types cimport (
@@ -124,14 +126,6 @@ def node2vec(ResourceHandle resource_handle,
 
     """
 
-    # FIXME: import these modules here for now until a better pattern can be
-    # used for optional imports (perhaps 'import_optional()' from cugraph), or
-    # these are made hard dependencies.
-    try:
-        import cupy
-    except ModuleNotFoundError:
-        raise RuntimeError("node2vec requires the cupy package, which could not "
-                           "be imported")
     assert_CAI_type(seed_array, "seed_array")
 
     cdef cugraph_resource_handle_t* c_resource_handle_ptr = \

python/pylibcugraph/pylibcugraph/pagerank.pyx

@@ -1,4 +1,4 @@
-# Copyright (c) 2022-2024, NVIDIA CORPORATION.
+# Copyright (c) 2022-2025, NVIDIA CORPORATION.
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
@@ -14,6 +14,9 @@
 # Have cython use python 3 syntax
 # cython: language_level = 3
 
+import cupy
+import numpy
+
 from pylibcugraph._cugraph_c.types cimport (
     bool_t,
 )
@@ -167,20 +170,6 @@ def pagerank(ResourceHandle resource_handle,
     array([0.11615585, 0.21488841, 0.2988108 , 0.3701449 ], dtype=float32)
     """
 
-    # FIXME: import these modules here for now until a better pattern can be
-    # used for optional imports (perhaps 'import_optional()' from cugraph), or
-    # these are made hard dependencies.
-    try:
-        import cupy
-    except ModuleNotFoundError:
-        raise RuntimeError("pagerank requires the cupy package, which could "
-                           "not be imported")
-    try:
-        import numpy
-    except ModuleNotFoundError:
-        raise RuntimeError("pagerank requires the numpy package, which could "
-                           "not be imported")
-
     cdef cugraph_type_erased_device_array_view_t* \
         initial_guess_vertices_view_ptr = \
             create_cugraph_type_erased_device_array_view_from_py_obj(

python/pylibcugraph/pylibcugraph/personalized_pagerank.pyx

@@ -1,4 +1,4 @@
-# Copyright (c) 2022-2024, NVIDIA CORPORATION.
+# Copyright (c) 2022-2025, NVIDIA CORPORATION.
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
@@ -14,6 +14,9 @@
 # Have cython use python 3 syntax
 # cython: language_level = 3
 
+import cupy
+import numpy
+
 from pylibcugraph._cugraph_c.types cimport (
     bool_t,
 )
@@ -177,20 +180,6 @@ def personalized_pagerank(ResourceHandle resource_handle,
     array([0.00446455, 0.00379487, 0.53607565, 0.45566472 ], dtype=float32)
     """
 
-    # FIXME: import these modules here for now until a better pattern can be
-    # used for optional imports (perhaps 'import_optional()' from cugraph), or
-    # these are made hard dependencies.
-    try:
-        import cupy
-    except ModuleNotFoundError:
-        raise RuntimeError("pagerank requires the cupy package, which could "
-                           "not be imported")
-    try:
-        import numpy
-    except ModuleNotFoundError:
-        raise RuntimeError("pagerank requires the numpy package, which could "
-                           "not be imported")
-
     cdef cugraph_type_erased_device_array_view_t* \
         initial_guess_vertices_view_ptr = \
             create_cugraph_type_erased_device_array_view_from_py_obj(

python/pylibcugraph/pylibcugraph/sssp.pyx

@@ -1,4 +1,4 @@
-# Copyright (c) 2022-2024, NVIDIA CORPORATION.
+# Copyright (c) 2022-2025, NVIDIA CORPORATION.
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
@@ -14,6 +14,9 @@
 # Have cython use python 3 syntax
 # cython: language_level = 3
 
+import cupy
+import numpy
+
 from pylibcugraph._cugraph_c.types cimport (
     bool_t,
 )
@@ -124,20 +127,6 @@ def sssp(ResourceHandle resource_handle,
     array([-1, -1,  1,  2], dtype=int32)
     """
 
-    # FIXME: import these modules here for now until a better pattern can be
-    # used for optional imports (perhaps 'import_optional()' from cugraph), or
-    # these are made hard dependencies.
-    try:
-        import cupy
-    except ModuleNotFoundError:
-        raise RuntimeError("sssp requires the cupy package, which could not "
-                           "be imported")
-    try:
-        import numpy
-    except ModuleNotFoundError:
-        raise RuntimeError("sssp requires the numpy package, which could not "
-                           "be imported")
-
     if compute_predecessors is False:
         raise ValueError("compute_predecessors must be True for the current "
                          "release.")

python/pylibcugraph/pyproject.toml

@@ -23,6 +23,8 @@ authors = [
 license = { text = "Apache 2.0" }
 requires-python = ">=3.10"
 dependencies = [
+    "cupy-cuda11x>=12.0.0",
+    "numpy>=1.23,<3.0a0",
     "nvidia-cublas",
     "nvidia-curand",
     "nvidia-cusolver",