Add EMST example

examples/CMakeLists.txt

@@ -10,6 +10,7 @@ add_subdirectory(brute_force)
 add_subdirectory(callback)
 add_subdirectory(custom_distance)
 add_subdirectory(dbscan)
+add_subdirectory(emst)
 add_subdirectory(molecular_dynamics)
 add_subdirectory(simple_intersection)
 add_subdirectory(triangle_intersection)

examples/README.md

@@ -7,6 +7,7 @@ Directory | Description
 `callback`              | execute search which calls user function on match
 `custom_distance`       | execute nearest search using a custom distance metric
 `dbscan`                | cluster a set of points using DBSCAN
+`emst`                  | build an Euclidean minimum spanning tree (MST)
 `molecular_dynamics`    | do one step of moving particles under forces
 `moving_least_squares`  | interpolate data between point clouds using MLS
 `raytracing`            | deposit ray energy onto intersected boxes

examples/emst/CMakeLists.txt

@@ -0,0 +1,3 @@
+add_executable(ArborX_Example_EMST.exe example_emst.cpp)
+target_link_libraries(ArborX_Example_EMST.exe ArborX::ArborX)
+add_test(NAME ArborX_Example_EMST COMMAND ArborX_Example_EMST.exe)

examples/emst/example_emst.cpp

@@ -0,0 +1,72 @@
+/****************************************************************************
+ * Copyright (c) 2025, ArborX authors                                       *
+ * All rights reserved.                                                     *
+ *                                                                          *
+ * This file is part of the ArborX library. ArborX is                       *
+ * distributed under a BSD 3-clause license. For the licensing terms see    *
+ * the LICENSE file in the top-level directory.                             *
+ *                                                                          *
+ * SPDX-License-Identifier: BSD-3-Clause                                    *
+ ****************************************************************************/
+
+#include <ArborX_MinimumSpanningTree.hpp>
+
+#include <Kokkos_Sort.hpp>
+
+#include <iostream>
+
+template <typename MemorySpace>
+void printEdges(
+    Kokkos::View<ArborX::Experimental::WeightedEdge *, MemorySpace> edges)
+{
+  auto edges_host =
+      Kokkos::create_mirror_view_and_copy(Kokkos::HostSpace{}, edges);
+  Kokkos::sort(edges_host);
+  for (int i = 0; i < (int)edges_host.size(); ++i)
+  {
+    auto const &edge = edges_host(i);
+    auto min_index = std::min(edge.source, edge.target);
+    auto max_index = std::max(edge.source, edge.target);
+    printf("#%d: (%d, %d, %.2f)\n", i, min_index, max_index, edge.weight);
+  }
+}
+
+int main(int argc, char *argv[])
+{
+  Kokkos::ScopeGuard guard(argc, argv);
+
+  using ExecutionSpace = Kokkos::DefaultExecutionSpace;
+  using MemorySpace = ExecutionSpace::memory_space;
+
+  Kokkos::View<ArborX::Point<2> *, MemorySpace> cloud("Example::point_cloud",
+                                                      6);
+  auto cloud_host = Kokkos::create_mirror_view(cloud);
+  // 4 |     5
+  // 3 |   2 4
+  // 2 |         3
+  // 1 | 1
+  // 0 |   0
+  //    ----------
+  //     0 1 2 3 4
+  cloud_host[0] = {1, 0};
+  cloud_host[1] = {0, 1};
+  cloud_host[2] = {1, 3};
+  cloud_host[3] = {4, 2};
+  cloud_host[4] = {2, 3};
+  cloud_host[5] = {2, 4};
+  Kokkos::deep_copy(cloud, cloud_host);
+
+  ArborX::Experimental::MinimumSpanningTree<MemorySpace> emst(ExecutionSpace{},
+                                                              cloud);
+  auto edges = emst.edges;
+
+  // Expected output:
+  // #0: (2, 4, 1.00)
+  // #1: (4, 5, 1.00)
+  // #2: (0, 1, 1.41)
+  // #3: (3, 4, 2.24)
+  // #4: (1, 2, 2.24)
+  printEdges(edges);
+
+  return 0;
+}