added cpp boilerplate

csrc/knn.cpp

+#include <Python.h>
+#include <torch/script.h>
+
+#ifdef WITH_CUDA
+#include "cuda/knn_cuda.h"
+#endif
+
+#ifdef _WIN32
+PyMODINIT_FUNC PyInit__knn(void) { return NULL; }
+#endif
+
+torch::Tensor knn(torch::Tensor x, torch::Tensor y, torch::Tensor ptr_x,
+                  torch::Tensor ptr_y, int64_t k, bool cosine) {
+  if (x.device().is_cuda()) {
+#ifdef WITH_CUDA
+    return knn_cuda(x, y, ptr_x, ptr_y, k, cosine);
+#else
+    AT_ERROR("Not compiled with CUDA support");
+#endif
+  } else {
+    AT_ERROR("No CPU version supported");
+  }
+}
+
+static auto registry =
+    torch::RegisterOperators().op("torch_cluster::knn", &knn);

csrc/nearest.cpp

+#include <Python.h>
+#include <torch/script.h>
+
+#ifdef WITH_CUDA
+#include "cuda/nearest_cuda.h"
+#endif
+
+#ifdef _WIN32
+PyMODINIT_FUNC PyInit__nearest(void) { return NULL; }
+#endif
+
+torch::Tensor nearest(torch::Tensor x, torch::Tensor y, torch::Tensor ptr_x,
+                      torch::Tensor ptr_y) {
+  if (x.device().is_cuda()) {
+#ifdef WITH_CUDA
+    return nearest_cuda(x, y, ptr_x, ptr_y);
+#else
+    AT_ERROR("Not compiled with CUDA support");
+#endif
+  } else {
+    AT_ERROR("No CPU version supported");
+  }
+}
+
+static auto registry =
+    torch::RegisterOperators().op("torch_cluster::nearest", &nearest);

csrc/radius.cpp

+#include <Python.h>
+#include <torch/script.h>
+
+#ifdef WITH_CUDA
+#include "cuda/radius_cuda.h"
+#endif
+
+#ifdef _WIN32
+PyMODINIT_FUNC PyInit__radius(void) { return NULL; }
+#endif
+
+torch::Tensor radius(torch::Tensor x, torch::Tensor y, torch::Tensor ptr_x,
+                     torch::Tensor ptr_y, double r, int64_t max_num_neighbors) {
+  if (x.device().is_cuda()) {
+#ifdef WITH_CUDA
+    return radius_cuda(x, y, ptr_x, ptr_y, r, max_num_neighbors);
+#else
+    AT_ERROR("Not compiled with CUDA support");
+#endif
+  } else {
+    AT_ERROR("No CPU version supported");
+  }
+}
+
+static auto registry =
+    torch::RegisterOperators().op("torch_cluster::radius", &radius);

torch_cluster/__init__.py

@@ -8,7 +8,8 @@ expected_torch_version = (1, 4)
 
 try:
     for library in [
-            '_version', '_grid', '_graclus', '_fps', '_rw', '_sampler'
+            '_version', '_grid', '_graclus', '_fps', '_rw', '_sampler',
+            '_nearest', '_knn', '_radius'
     ]:
         torch.ops.load_library(importlib.machinery.PathFinder().find_spec(
             library, [osp.dirname(__file__)]).origin)