Drop uses of thrust/functional.h (#1835)

Authors:
  - Michael Schellenberger Costa (https://github.com/miscco)
  - Anupam (https://github.com/aamijar)

Approvers:
  - Micka (https://github.com/lowener)
  - Anupam (https://github.com/aamijar)

URL: #1835

Author: miscco

cpp/src/cluster/detail/agglomerative.cuh

@@ -14,13 +14,13 @@
 #include <rmm/device_uvector.hpp>
 
 #include <cuda/iterator>
+#include <cuda/std/functional>
 #include <cuda/std/tuple>
 #include <thrust/device_ptr.h>
 #include <thrust/execution_policy.h>
 #include <thrust/extrema.h>
 #include <thrust/fill.h>
 #include <thrust/for_each.h>
-#include <thrust/functional.h>
 #include <thrust/iterator/zip_iterator.h>
 #include <thrust/sort.h>
 
@@ -282,7 +282,7 @@ void extract_flattened_clusters(raft::resources const& handle,
     thrust::sort(thrust_policy,
                  label_roots.data(),
                  label_roots.data() + (child_size),
-                 thrust::greater<value_idx>());
+                 cuda::std::greater<value_idx>());
 
     rmm::device_uvector<value_idx> tmp_labels(n_vertices, stream);
 

cpp/src/neighbors/ball_cover/ball_cover.cuh

@@ -25,7 +25,6 @@
 
 #include <cuda/std/tuple>
 #include <thrust/fill.h>
-#include <thrust/functional.h>
 #include <thrust/iterator/zip_iterator.h>
 #include <thrust/reduce.h>
 #include <thrust/sort.h>

cpp/src/neighbors/ball_cover/common.cuh

@@ -6,7 +6,6 @@
 #pragma once
 
 #include <cuda/std/tuple>
-#include <thrust/functional.h>
 
 #include <cstdint>
 

cpp/src/neighbors/ball_cover/registers.cuh

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: Copyright (c) 2025, NVIDIA CORPORATION.
+ * SPDX-FileCopyrightText: Copyright (c) 2025-2026, NVIDIA CORPORATION.
  * SPDX-License-Identifier: Apache-2.0
  */
 
@@ -17,6 +17,7 @@
 #include <raft/linalg/unary_op.cuh>
 #include <raft/util/cuda_utils.cuh>
 
+#include <cuda/functional>
 #include <thrust/count.h>
 #include <thrust/fill.h>
 #include <thrust/scan.h>
@@ -1444,7 +1445,7 @@ void rbc_eps_pass(raft::resources const& handle,
                                         vd_ptr,
                                         vd_ptr + n_query_rows,
                                         (value_idx)0,
-                                        thrust::maximum<value_idx>());
+                                        cuda::maximum<value_idx>());
 
     if (actual_max > max_k_in) {
       // ceil vd to max_k