Don't setup managed memory if rmm isn't using default settings

Previously `cuml.accel` would always install a new
`ManagedMemoryResource` on for the current device when installed. We now
only do this if rmm is using the default resource. If a user or library
has already configured rmm, we continue using their settings.

This lets `cuml.accel` compose better with `cudf.pandas`, since we won't
clobber their memory resource setup after loading ours.

Also added tests for the `cuml.accel` IPython magics, including tests
loading `cudf.pandas` before and after `cuml.accel`.

Author: jcrist

python/cuml/cuml/accel/core.py

@@ -86,10 +86,24 @@ def install(disable_uvm=False):
         if _is_concurrent_managed_access_supported():
             import rmm
 
-            logger.debug("cuML: Enabling managed memory...")
-            rmm.mr.set_current_device_resource(rmm.mr.ManagedMemoryResource())
+            mr = rmm.mr.get_current_device_resource()
+            if isinstance(mr, rmm.mr.ManagedMemoryResource):
+                # Nothing to do
+                pass
+            elif not isinstance(mr, rmm.mr.CudaMemoryResource):
+                logger.debug(
+                    "cuML: A non-default memory resource is already configured, "
+                    "skipping enabling managed memory."
+                )
+            else:
+                rmm.mr.set_current_device_resource(
+                    rmm.mr.ManagedMemoryResource()
+                )
+                logger.debug("cuML: Enabled managed memory.")
         else:
-            logger.warn("cuML: Could not enable managed memory.")
+            logger.debug(
+                "cuML: Could not enable managed memory on this platform."
+            )
 
     ACCEL.install()
     set_global_output_type("numpy")

python/cuml/cuml_accel_tests/test_magics.py

@@ -0,0 +1,98 @@
+# Copyright (c) 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
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import subprocess
+import sys
+from textwrap import dedent
+
+import pytest
+
+pytest.importorskip("IPython")
+
+
+SCRIPT_HEADER = """
+from IPython.core.interactiveshell import InteractiveShell
+from traitlets.config import Config
+c = Config()
+c.HistoryManager.hist_file = ":memory:"
+ip = InteractiveShell(config=c)
+"""
+
+
+def run_script(body):
+    script = SCRIPT_HEADER + dedent(body)
+
+    res = subprocess.run(
+        [sys.executable, "-c", script],
+        stderr=subprocess.STDOUT,
+        stdout=subprocess.PIPE,
+        text=True,
+    )
+    # Pull out attributes before assert for nicer error reporting on failure
+    returncode = res.returncode
+    stdout = res.stdout
+    assert returncode == 0, stdout
+
+
+def test_magic():
+    run_script(
+        """
+        ip.run_line_magic("load_ext", "cuml.accel")
+
+        # cuml.accel proxies setup properly
+        ip.run_cell("from sklearn.linear_model import LinearRegression")
+        ip.run_cell("from cuml.accel import is_proxy")
+        ip.run_cell("assert is_proxy(LinearRegression)").raise_error()
+        """
+    )
+
+
+def test_magic_cudf_pandas_before():
+    run_script(
+        """
+        ip.run_line_magic("load_ext", "cudf.pandas")
+        ip.run_cell("import rmm; mr = rmm.mr.get_current_device_resource();")
+
+        ip.run_line_magic("load_ext", "cuml.accel")
+        ip.run_cell("mr2 = rmm.mr.get_current_device_resource();")
+
+        # cuml doesn't change the mr setup by cudf.pandas
+        ip.run_cell("assert mr is mr2").raise_error()
+
+        # cuml.accel proxies setup properly
+        ip.run_cell("from sklearn.linear_model import LinearRegression")
+        ip.run_cell("from cuml.accel import is_proxy")
+        result = ip.run_cell("assert is_proxy(LinearRegression)").raise_error()
+        """
+    )
+
+
+def test_magic_cudf_pandas_after():
+    run_script(
+        """
+        ip.run_line_magic("load_ext", "cuml.accel")
+        ip.run_cell("import rmm; mr = rmm.mr.get_current_device_resource();")
+
+        ip.run_line_magic("load_ext", "cudf.pandas")
+        ip.run_cell("mr2 = rmm.mr.get_current_device_resource();")
+
+        # cudf.pandas doesn't change the mr setup by cuml.accel
+        ip.run_cell("assert mr is mr2").raise_error()
+
+        # cuml.accel proxies setup properly
+        ip.run_cell("from sklearn.linear_model import LinearRegression")
+        ip.run_cell("from cuml.accel import is_proxy")
+        result = ip.run_cell("assert is_proxy(LinearRegression)").raise_error()
+        """
+    )