Migrate RMM usage to CCCL MR design (#2996)

## Summary
- Remove `device_memory_resource` base class usage, de-template all resource and adaptor types, replace pointer-based per-device resource APIs with ref-based equivalents
- Part of rapidsai/rmm#2011. Migration guide: rapidsai/rmm#2344.
- Supersedes #2917 and #2920

Depends on rapidsai/rmm#2361.
Depends on rapidsai/ucxx#636.

## Changes

### Core resource infrastructure
- **`device_memory_resource.hpp`**: Remove `any_resource_bridge` (which inherited from `rmm::mr::device_memory_resource`), remove all `shared_ptr<device_memory_resource>` constructor overloads, consolidate to `any_resource`-only path
- **`device_resources.hpp`**: Remove deprecated constructor taking `shared_ptr<device_memory_resource>`, update `get_workspace_resource()` return type (de-templated `limiting_resource_adaptor`)
- **`device_resources_snmg.hpp`**: Remove stale include, de-template `pool_memory_resource`
- **`handle.hpp`**: Remove deprecated constructors taking `shared_ptr<device_memory_resource>`
- **`device_resources_manager.hpp`**: Retype `workspace_mrs` vector from `shared_ptr<device_memory_resource>` to `raft::mr::device_resource`, update `set_workspace_memory_resource()` signature accordingly, de-template `pool_mr_` to `optional<pool_memory_resource>`, remove `dynamic_cast` for upstream type detection, replace `get/set_current_device_resource()` with `_ref` variants

### Memory tracking
- **`memory_tracking_resources.hpp`**: Remove `device_tracking_bridge` (inherited from `device_memory_resource`), use `set_current_device_resource_ref()` directly

### Call sites using `get_workspace_resource()` → `get_workspace_resource_ref()`
- `select_k-inl.cuh`, `select_radix.cuh`, `select_warpsort.cuh`, `sparse/select_k-inl.cuh`, `bitmap_to_csr.cuh`, `bitset_to_csr.cuh`

### Benchmarks
- **`benchmark.hpp`**: De-template `pool_memory_resource`, use `any_resource` for RAII restore
- **`gather.cu`**, **`subsample.cu`**: Same pattern

### Tests
- **`handle.cpp`**: Dereference `limiting_resource_adaptor*` for `device_buffer` constructor
- **`device_resources_manager.cpp`**: Remove workspace-related test code for removed APIs
- **`mdarray.cu`**: Remove `test_device_resource_bridge_unwrap` (bridge no longer exists)
- **`multi_variable_gaussian.cu`**: `get_current_device_resource()` → `get_current_device_resource_ref()`

Authors:
  - Bradley Dice (https://github.com/bdice)

Approvers:
  - Divye Gala (https://github.com/divyegala)

URL: #2996

Author: bdice

cpp/bench/prims/common/benchmark.hpp

@@ -17,7 +17,7 @@
 #include <rmm/cuda_stream.hpp>
 #include <rmm/cuda_stream_view.hpp>
 #include <rmm/device_buffer.hpp>
-#include <rmm/mr/device_memory_resource.hpp>
+#include <rmm/mr/cuda_memory_resource.hpp>
 #include <rmm/mr/per_device_resource.hpp>
 #include <rmm/mr/pool_memory_resource.hpp>
 
@@ -33,26 +33,23 @@ namespace raft::bench {
  */
 struct using_pool_memory_res {
  private:
-  rmm::mr::device_memory_resource* orig_res_;
-  rmm::mr::cuda_memory_resource cuda_res_{};
-  rmm::mr::pool_memory_resource<rmm::mr::device_memory_resource> pool_res_;
+  rmm::mr::pool_memory_resource pool_res_;
+  cuda::mr::any_resource<cuda::mr::device_accessible> prev_res_;
 
  public:
   using_pool_memory_res(size_t initial_size, size_t max_size)
-    : orig_res_(rmm::mr::get_current_device_resource()),
-      pool_res_(&cuda_res_, initial_size, max_size)
+    : pool_res_(rmm::mr::cuda_memory_resource{}, initial_size, max_size),
+      prev_res_(rmm::mr::set_current_device_resource(pool_res_))
   {
-    rmm::mr::set_current_device_resource(&pool_res_);
   }
 
   using_pool_memory_res()
-    : orig_res_(rmm::mr::get_current_device_resource()),
-      pool_res_(&cuda_res_, rmm::percent_of_free_device_memory(50))
+    : pool_res_(rmm::mr::cuda_memory_resource{}, rmm::percent_of_free_device_memory(50)),
+      prev_res_(rmm::mr::set_current_device_resource(pool_res_))
   {
-    rmm::mr::set_current_device_resource(&pool_res_);
   }
 
-  ~using_pool_memory_res() { rmm::mr::set_current_device_resource(orig_res_); }
+  ~using_pool_memory_res() { rmm::mr::set_current_device_resource(prev_res_); }
 };
 
 /**

cpp/bench/prims/matrix/gather.cu

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: Copyright (c) 2023-2025, NVIDIA CORPORATION.
+ * SPDX-FileCopyrightText: Copyright (c) 2023-2026, NVIDIA CORPORATION.
  * SPDX-License-Identifier: Apache-2.0
  */
 
@@ -13,7 +13,7 @@
 #include <raft/util/itertools.hpp>
 
 #include <rmm/device_uvector.hpp>
-#include <rmm/mr/device_memory_resource.hpp>
+#include <rmm/mr/per_device_resource.hpp>
 #include <rmm/mr/pool_memory_resource.hpp>
 
 namespace raft::bench::matrix {
@@ -35,18 +35,17 @@ template <typename T, typename MapT, typename IdxT, bool Conditional = false>
 struct Gather : public fixture {
   Gather(const GatherParams<IdxT>& p)
     : params(p),
-      old_mr(rmm::mr::get_current_device_resource()),
-      pool_mr(rmm::mr::get_current_device_resource(), 2 * (1ULL << 30)),
+      pool_mr(rmm::mr::get_current_device_resource_ref(), 2 * (1ULL << 30)),
+      prev_res_(rmm::mr::set_current_device_resource(pool_mr)),
       matrix(this->handle),
       map(this->handle),
       out(this->handle),
       stencil(this->handle),
       matrix_h(this->handle)
   {
-    rmm::mr::set_current_device_resource(&pool_mr);
   }
 
-  ~Gather() { rmm::mr::set_current_device_resource(old_mr); }
+  ~Gather() { rmm::mr::set_current_device_resource(prev_res_); }
 
   void allocate_data(const ::benchmark::State& state) override
   {
@@ -107,8 +106,8 @@ struct Gather : public fixture {
 
  private:
   GatherParams<IdxT> params;
-  rmm::mr::device_memory_resource* old_mr;
-  rmm::mr::pool_memory_resource<rmm::mr::device_memory_resource> pool_mr;
+  rmm::mr::pool_memory_resource pool_mr;
+  cuda::mr::any_resource<cuda::mr::device_accessible> prev_res_;
   raft::device_matrix<T, IdxT> matrix, out;
   raft::host_matrix<T, IdxT> matrix_h;
   raft::device_vector<T, IdxT> stencil;

cpp/bench/prims/random/subsample.cu

@@ -50,16 +50,15 @@ template <typename T>
 struct sample : public fixture {
   sample(const sample_inputs& p)
     : params(p),
-      old_mr(rmm::mr::get_current_device_resource()),
-      pool_mr(rmm::mr::get_current_device_resource(), 2 * GiB),
+      pool_mr(rmm::mr::get_current_device_resource_ref(), 2 * GiB),
+      prev_mr(rmm::mr::set_current_device_resource(pool_mr)),
       in(make_device_vector<T, int64_t>(res, p.n_samples)),
       out(make_device_vector<T, int64_t>(res, p.n_train))
   {
-    rmm::mr::set_current_device_resource(&pool_mr);
     raft::random::RngState r(123456ULL);
   }
 
-  ~sample() { rmm::mr::set_current_device_resource(old_mr); }
+  ~sample() { rmm::mr::set_current_device_resource(prev_mr); }
   void run_benchmark(::benchmark::State& state) override
   {
     std::ostringstream label_stream;
@@ -81,8 +80,8 @@ struct sample : public fixture {
  private:
   float GiB = 1073741824.0f;
   raft::device_resources res;
-  rmm::mr::device_memory_resource* old_mr;
-  rmm::mr::pool_memory_resource<rmm::mr::device_memory_resource> pool_mr;
+  rmm::mr::pool_memory_resource pool_mr;
+  cuda::mr::any_resource<cuda::mr::device_accessible> prev_mr;
   sample_inputs params;
   raft::device_vector<T, int64_t> out, in;
 };  // struct sample

cpp/include/raft/core/device_resources.hpp

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: Copyright (c) 2019-2025, NVIDIA CORPORATION.
+ * SPDX-FileCopyrightText: Copyright (c) 2019-2026, NVIDIA CORPORATION.
  * SPDX-License-Identifier: Apache-2.0
  */
 
@@ -26,7 +26,7 @@
 
 #include <rmm/cuda_stream_pool.hpp>
 #include <rmm/exec_policy.hpp>
-#include <rmm/mr/device_memory_resource.hpp>
+#include <rmm/resource_ref.hpp>
 
 #include <cuda_runtime.h>
 
@@ -52,12 +52,11 @@ namespace raft {
 class device_resources : public resources {
  public:
   device_resources(const device_resources& handle,
-                   std::shared_ptr<rmm::mr::device_memory_resource> workspace_resource,
+                   raft::mr::device_resource workspace_resource,
                    std::optional<std::size_t> allocation_limit = std::nullopt)
     : resources{handle}
   {
-    // replace the resource factory for the workspace_resources
-    resource::set_workspace_resource(*this, workspace_resource, allocation_limit);
+    resource::set_workspace_resource(*this, std::move(workspace_resource), allocation_limit);
   }
 
   device_resources(const device_resources& handle) : resources{handle} {}
@@ -77,8 +76,8 @@ class device_resources : public resources {
    */
   device_resources(rmm::cuda_stream_view stream_view                  = rmm::cuda_stream_per_thread,
                    std::shared_ptr<rmm::cuda_stream_pool> stream_pool = {nullptr},
-                   std::shared_ptr<rmm::mr::device_memory_resource> workspace_resource = {nullptr},
-                   std::optional<std::size_t> allocation_limit = std::nullopt)
+                   std::optional<raft::mr::device_resource> workspace_resource = std::nullopt,
+                   std::optional<std::size_t> allocation_limit                 = std::nullopt)
     : resources{}
   {
     resources::add_resource_factory(std::make_shared<resource::device_id_resource_factory>());
@@ -87,7 +86,7 @@ class device_resources : public resources {
     resources::add_resource_factory(
       std::make_shared<resource::cuda_stream_pool_resource_factory>(stream_pool));
     if (workspace_resource) {
-      resource::set_workspace_resource(*this, workspace_resource, allocation_limit);
+      resource::set_workspace_resource(*this, std::move(*workspace_resource), allocation_limit);
     }
   }
 
@@ -214,7 +213,7 @@ class device_resources : public resources {
     return resource::get_subcomm(*this, key);
   }
 
-  rmm::mr::device_memory_resource* get_workspace_resource() const
+  rmm::mr::limiting_resource_adaptor* get_workspace_resource() const
   {
     return resource::get_workspace_resource(*this);
   }

cpp/include/raft/core/device_resources_manager.hpp

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: Copyright (c) 2023-2025, NVIDIA CORPORATION.
+ * SPDX-FileCopyrightText: Copyright (c) 2023-2026, NVIDIA CORPORATION.
  * SPDX-License-Identifier: Apache-2.0
  */
 
@@ -12,6 +12,7 @@
 #include <rmm/cuda_stream_pool.hpp>
 #include <rmm/mr/cuda_memory_resource.hpp>
 #include <rmm/mr/per_device_resource.hpp>
+#include <rmm/mr/pool_memory_resource.hpp>
 
 #include <algorithm>
 #include <memory>
@@ -117,9 +118,7 @@ struct device_resources_manager {
     // Optional specification of separate workspace memory resources for each
     // device. The integer in each pair indicates the device for this memory
     // resource.
-    std::vector<std::pair<std::shared_ptr<rmm::mr::device_memory_resource>, int>> workspace_mrs{};
-
-    auto get_workspace_memory_resource(int device_id) {}
+    std::vector<std::pair<raft::mr::device_resource, int>> workspace_mrs{};
   } params_;
 
   // This struct stores the underlying resources to be shared among
@@ -152,36 +151,31 @@ struct device_resources_manager {
         }()},
         pool_mr_{[&params, this]() {
           auto scoped_device = device_setter{device_id_};
-          auto result =
-            std::shared_ptr<rmm::mr::pool_memory_resource<rmm::mr::cuda_memory_resource>>{nullptr};
+          auto result        = std::optional<rmm::mr::pool_memory_resource>{};
           // If max_mem_pool_size is nullopt or non-zero, create a pool memory
           // resource
           if (params.max_mem_pool_size.value_or(1) != 0) {
-            auto* upstream =
-              dynamic_cast<rmm::mr::cuda_memory_resource*>(rmm::mr::get_current_device_resource());
-            if (upstream != nullptr) {
-              result =
-                std::make_shared<rmm::mr::pool_memory_resource<rmm::mr::cuda_memory_resource>>(
-                  upstream,
-                  params.init_mem_pool_size.value_or(rmm::percent_of_free_device_memory(50)),
-                  params.max_mem_pool_size);
-              rmm::mr::set_current_device_resource(result.get());
-            } else {
-              RAFT_LOG_WARN(
-                "Pool allocation requested, but other memory resource has already been set and "
-                "will not be overwritten");
-            }
+            // TODO: reinstate the dynamic_cast<cuda_memory_resource*> guard that
+            // skipped pool creation when a non-default resource was already set,
+            // once CCCL exposes resource_cast or an equivalent type-query.
+            auto upstream = rmm::mr::get_current_device_resource_ref();
+            result.emplace(
+              upstream,
+              params.init_mem_pool_size.value_or(rmm::percent_of_free_device_memory(50)),
+              params.max_mem_pool_size);
+            rmm::mr::set_current_device_resource(*result);
           }
           return result;
         }()},
         workspace_mr_{[&params, this]() {
-          auto result = std::shared_ptr<rmm::mr::device_memory_resource>{nullptr};
+          auto result = std::optional<raft::mr::device_resource>{};
           auto iter   = std::find_if(std::begin(params.workspace_mrs),
                                    std::end(params.workspace_mrs),
                                    [this](auto&& pair) { return pair.second == device_id_; });
           if (iter != std::end(params.workspace_mrs)) { result = iter->first; }
           return result;
-        }()}
+        }()},
+        workspace_allocation_limit_{params.workspace_allocation_limit}
     {
     }
 
@@ -216,26 +210,23 @@ struct device_resources_manager {
       if (pool_count() != 0) { result = pools_[get_thread_id() % pool_count()]; }
       return result;
     }
-    // Return a (possibly null) shared_ptr to the pool memory resource
-    // created for this device by the manager
-    [[nodiscard]] auto get_pool_memory_resource() const { return pool_mr_; }
+    // Return the pool memory resource created for this device by the manager (if any)
+    [[nodiscard]] auto& get_pool_memory_resource() { return pool_mr_; }
     // Return the RAFT workspace allocation limit that will be used by
     // `device_resources` returned from this manager
     [[nodiscard]] auto get_workspace_allocation_limit() const
     {
       return workspace_allocation_limit_;
     }
-    // Return a (possibly null) shared_ptr to the memory resource that will
-    // be used for workspace allocations by `device_resources` returned from
-    // this manager
-    [[nodiscard]] auto get_workspace_memory_resource() { return workspace_mr_; }
+    // Return the workspace memory resource for this device (if any)
+    [[nodiscard]] auto& get_workspace_memory_resource() { return workspace_mr_; }
 
    private:
     int device_id_;
     std::unique_ptr<rmm::cuda_stream_pool> streams_;
     std::vector<std::shared_ptr<rmm::cuda_stream_pool>> pools_;
-    std::shared_ptr<rmm::mr::pool_memory_resource<rmm::mr::cuda_memory_resource>> pool_mr_;
-    std::shared_ptr<rmm::mr::device_memory_resource> workspace_mr_;
+    std::optional<rmm::mr::pool_memory_resource> pool_mr_;
+    std::optional<raft::mr::device_resource> workspace_mr_;
     std::optional<std::size_t> workspace_allocation_limit_{std::nullopt};
   };
 
@@ -374,8 +365,7 @@ struct device_resources_manager {
   }
 
   // Thread-safe setter for workspace memory resources
-  void set_workspace_memory_resource_(std::shared_ptr<rmm::mr::device_memory_resource> mr,
-                                      int device_id)
+  void set_workspace_memory_resource_(raft::mr::device_resource mr, int device_id)
   {
     auto lock = get_lock();
     if (params_finalized_) {
@@ -387,9 +377,9 @@ struct device_resources_manager {
                                std::end(params_.workspace_mrs),
                                [device_id](auto&& pair) { return pair.second == device_id; });
       if (iter != std::end(params_.workspace_mrs)) {
-        iter->first = mr;
+        iter->first = std::move(mr);
       } else {
-        params_.workspace_mrs.emplace_back(mr, device_id);
+        params_.workspace_mrs.emplace_back(std::move(mr), device_id);
       }
     }
   }
@@ -548,7 +538,7 @@ struct device_resources_manager {
    * @brief Set the workspace memory resource to be used on a specific device
    *
    * RAFT device_resources objects can be built with a separate memory
-   * resource for allocating temporary workspaces. If a (non-nullptr) memory
+   * resource for allocating temporary workspaces. If a memory
    * resource is provided by this setter, it will be used as the
    * workspace memory resource for all `device_resources` returned for the
    * indicated device.
@@ -557,10 +547,10 @@ struct device_resources_manager {
    * `raft::device_resources_manager::get_device_resources`, no change will be made,
    * and a warning will be emitted.
    */
-  static void set_workspace_memory_resource(std::shared_ptr<rmm::mr::device_memory_resource> mr,
+  static void set_workspace_memory_resource(raft::mr::device_resource mr,
                                             int device_id = device_setter::get_current_device())
   {
-    get_manager().set_workspace_memory_resource_(mr, device_id);
+    get_manager().set_workspace_memory_resource_(std::move(mr), device_id);
   }
 };
 }  // namespace raft

cpp/include/raft/core/device_resources_snmg.hpp

@@ -10,7 +10,6 @@
 #include <raft/core/resource/resource_types.hpp>
 
 #include <rmm/cuda_device.hpp>
-#include <rmm/mr/device_memory_resource.hpp>
 #include <rmm/mr/per_device_resource.hpp>
 #include <rmm/mr/pool_memory_resource.hpp>
 
@@ -105,10 +104,9 @@ class device_resources_snmg : public device_resources {
       int device_id = raft::resource::get_device_id(dev_res);
       pool_device_ids_.push_back(device_id);
 
-      per_device_pools_.push_back(
-        std::make_unique<rmm::mr::pool_memory_resource<rmm::mr::device_memory_resource>>(
-          rmm::mr::get_current_device_resource_ref(),
-          rmm::percent_of_free_device_memory(percent_of_free_memory)));
+      per_device_pools_.push_back(std::make_unique<rmm::mr::pool_memory_resource>(
+        rmm::mr::get_current_device_resource_ref(),
+        rmm::percent_of_free_device_memory(percent_of_free_memory)));
       rmm::mr::set_per_device_resource_ref(rmm::cuda_device_id{device_id},
                                            *per_device_pools_.back());
     }
@@ -151,8 +149,7 @@ class device_resources_snmg : public device_resources {
     }
   }
   int main_gpu_id_;
-  std::vector<std::unique_ptr<rmm::mr::pool_memory_resource<rmm::mr::device_memory_resource>>>
-    per_device_pools_;
+  std::vector<std::unique_ptr<rmm::mr::pool_memory_resource>> per_device_pools_;
   std::vector<int> pool_device_ids_;
 };  // class device_resources_snmg
 

cpp/include/raft/core/handle.hpp

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: Copyright (c) 2019-2023, NVIDIA CORPORATION.
+ * SPDX-FileCopyrightText: Copyright (c) 2019-2026, NVIDIA CORPORATION.
  * SPDX-License-Identifier: Apache-2.0
  */
 
@@ -21,9 +21,8 @@ namespace raft {
  */
 class handle_t : public raft::device_resources {
  public:
-  handle_t(const handle_t& handle,
-           std::shared_ptr<rmm::mr::device_memory_resource> workspace_resource)
-    : device_resources(handle, workspace_resource)
+  handle_t(const handle_t& handle, raft::mr::device_resource workspace_resource)
+    : device_resources(handle, std::move(workspace_resource))
   {
   }
 
@@ -43,8 +42,8 @@ class handle_t : public raft::device_resources {
    */
   handle_t(rmm::cuda_stream_view stream_view                  = rmm::cuda_stream_per_thread,
            std::shared_ptr<rmm::cuda_stream_pool> stream_pool = {nullptr},
-           std::shared_ptr<rmm::mr::device_memory_resource> workspace_resource = {nullptr})
-    : device_resources{stream_view, stream_pool, workspace_resource}
+           std::optional<raft::mr::device_resource> workspace_resource = std::nullopt)
+    : device_resources{stream_view, stream_pool, std::move(workspace_resource)}
   {
   }