Count self-loops and multi-edges (#1939)

Close #537

Count the number of self-loops & multi-edges.

- [x] API update
- [x] Implement count self-loops
- [x] Implement count multi-edges
- [x] Add C++ test suites.

Authors:
  - Seunghwa Kang (https://github.com/seunghwak)

Approvers:
  - Chuck Hastings (https://github.com/ChuckHastings)
  - Kumar Aatish (https://github.com/kaatish)

URL: #1939

cpp/include/cugraph/detail/decompress_matrix_partition.cuh

@@ -55,7 +55,7 @@ __global__ void for_all_major_for_all_nbr_mid_degree(
     auto major =
       matrix_partition.get_major_from_major_offset_nocheck(static_cast<vertex_t>(major_offset));
     vertex_t const* indices{nullptr};
-    thrust::optional<weight_t const*> weights{nullptr};
+    thrust::optional<weight_t const*> weights{thrust::nullopt};
     edge_t local_degree{};
     thrust::tie(indices, weights, local_degree) = matrix_partition.get_local_edges(major_offset);
     auto local_offset                           = matrix_partition.get_local_offset(major_offset);
@@ -81,7 +81,7 @@ __global__ void for_all_major_for_all_nbr_high_degree(
     auto major =
       matrix_partition.get_major_from_major_offset_nocheck(static_cast<vertex_t>(major_offset));
     vertex_t const* indices{nullptr};
-    thrust::optional<weight_t const*> weights{nullptr};
+    thrust::optional<weight_t const*> weights{thrust::nullopt};
     edge_t local_degree{};
     thrust::tie(indices, weights, local_degree) =
       matrix_partition.get_local_edges(static_cast<vertex_t>(major_offset));

cpp/include/cugraph/graph_view.hpp

@@ -599,6 +599,9 @@ class graph_view_t<vertex_t,
   weight_t compute_max_in_weight_sum(raft::handle_t const& handle) const;
   weight_t compute_max_out_weight_sum(raft::handle_t const& handle) const;
 
+  edge_t count_self_loops(raft::handle_t const& handle) const;
+  edge_t count_multi_edges(raft::handle_t const& handle) const;
+
   std::optional<vertex_t const*> get_local_sorted_unique_edge_row_begin() const
   {
     return local_sorted_unique_edge_row_first_;
@@ -833,6 +836,9 @@ class graph_view_t<vertex_t,
   weight_t compute_max_in_weight_sum(raft::handle_t const& handle) const;
   weight_t compute_max_out_weight_sum(raft::handle_t const& handle) const;
 
+  edge_t count_self_loops(raft::handle_t const& handle) const;
+  edge_t count_multi_edges(raft::handle_t const& handle) const;
+
   std::optional<vertex_t const*> get_local_sorted_unique_edge_row_begin() const
   {
     return std::nullopt;

cpp/include/cugraph/prims/copy_v_transform_reduce_in_out_nbr.cuh

@@ -85,7 +85,7 @@ __global__ void for_all_major_for_all_nbr_hypersparse(
     auto major_idx =
       major_start_offset + idx;  // major_offset != major_idx in the hypersparse region
     vertex_t const* indices{nullptr};
-    thrust::optional<weight_t const*> weights{nullptr};
+    thrust::optional<weight_t const*> weights{thrust::nullopt};
     edge_t local_degree{};
     thrust::tie(indices, weights, local_degree) =
       matrix_partition.get_local_edges(static_cast<vertex_t>(major_idx));
@@ -195,7 +195,7 @@ __global__ void for_all_major_for_all_nbr_low_degree(
   while (idx < static_cast<size_t>(major_last - major_first)) {
     auto major_offset = major_start_offset + idx;
     vertex_t const* indices{nullptr};
-    thrust::optional<weight_t const*> weights{nullptr};
+    thrust::optional<weight_t const*> weights{thrust::nullopt};
     edge_t local_degree{};
     thrust::tie(indices, weights, local_degree) =
       matrix_partition.get_local_edges(static_cast<vertex_t>(major_offset));
@@ -316,7 +316,7 @@ __global__ void for_all_major_for_all_nbr_mid_degree(
   while (idx < static_cast<size_t>(major_last - major_first)) {
     auto major_offset = major_start_offset + idx;
     vertex_t const* indices{nullptr};
-    thrust::optional<weight_t const*> weights{nullptr};
+    thrust::optional<weight_t const*> weights{thrust::nullopt};
     edge_t local_degree{};
     thrust::tie(indices, weights, local_degree) = matrix_partition.get_local_edges(major_offset);
     [[maybe_unused]] auto e_op_result_sum =
@@ -409,7 +409,7 @@ __global__ void for_all_major_for_all_nbr_high_degree(
   while (idx < static_cast<size_t>(major_last - major_first)) {
     auto major_offset = major_start_offset + idx;
     vertex_t const* indices{nullptr};
-    thrust::optional<weight_t const*> weights{nullptr};
+    thrust::optional<weight_t const*> weights{thrust::nullopt};
     edge_t local_degree{};
     thrust::tie(indices, weights, local_degree) = matrix_partition.get_local_edges(major_offset);
     [[maybe_unused]] auto e_op_result_sum =

cpp/include/cugraph/prims/transform_reduce_by_adj_matrix_row_col_key_e.cuh

@@ -117,7 +117,7 @@ __global__ void for_all_major_for_all_nbr_hypersparse(
     auto major_idx =
       major_start_offset + idx;  // major_offset != major_idx in the hypersparse region
     vertex_t const* indices{nullptr};
-    thrust::optional<weight_t const*> weights{nullptr};
+    thrust::optional<weight_t const*> weights{thrust::nullopt};
     edge_t local_degree{};
     thrust::tie(indices, weights, local_degree) =
       matrix_partition.get_local_edges(static_cast<vertex_t>(major_idx));
@@ -174,7 +174,7 @@ __global__ void for_all_major_for_all_nbr_low_degree(
     auto major =
       matrix_partition.get_major_from_major_offset_nocheck(static_cast<vertex_t>(major_offset));
     vertex_t const* indices{nullptr};
-    thrust::optional<weight_t const*> weights{nullptr};
+    thrust::optional<weight_t const*> weights{thrust::nullopt};
     edge_t local_degree{};
     thrust::tie(indices, weights, local_degree) =
       matrix_partition.get_local_edges(static_cast<vertex_t>(major_offset));
@@ -234,7 +234,7 @@ __global__ void for_all_major_for_all_nbr_mid_degree(
     auto major =
       matrix_partition.get_major_from_major_offset_nocheck(static_cast<vertex_t>(major_offset));
     vertex_t const* indices{nullptr};
-    thrust::optional<weight_t const*> weights{nullptr};
+    thrust::optional<weight_t const*> weights{thrust::nullopt};
     edge_t local_degree{};
     thrust::tie(indices, weights, local_degree) =
       matrix_partition.get_local_edges(static_cast<vertex_t>(major_offset));
@@ -290,7 +290,7 @@ __global__ void for_all_major_for_all_nbr_high_degree(
     auto major =
       matrix_partition.get_major_from_major_offset_nocheck(static_cast<vertex_t>(major_offset));
     vertex_t const* indices{nullptr};
-    thrust::optional<weight_t const*> weights{nullptr};
+    thrust::optional<weight_t const*> weights{thrust::nullopt};
     edge_t local_degree{};
     thrust::tie(indices, weights, local_degree) =
       matrix_partition.get_local_edges(static_cast<vertex_t>(major_offset));

cpp/include/cugraph/prims/transform_reduce_e.cuh

@@ -76,7 +76,7 @@ __global__ void for_all_major_for_all_nbr_hypersparse(
     auto major_idx =
       major_start_offset + idx;  // major_offset != major_idx in the hypersparse region
     vertex_t const* indices{nullptr};
-    thrust::optional<weight_t const*> weights{nullptr};
+    thrust::optional<weight_t const*> weights{thrust::nullopt};
     edge_t local_degree{};
     thrust::tie(indices, weights, local_degree) = matrix_partition.get_local_edges(major_idx);
     auto sum                                    = thrust::transform_reduce(
@@ -159,7 +159,7 @@ __global__ void for_all_major_for_all_nbr_low_degree(
   while (idx < static_cast<size_t>(major_last - major_first)) {
     auto major_offset = major_start_offset + idx;
     vertex_t const* indices{nullptr};
-    thrust::optional<weight_t const*> weights{nullptr};
+    thrust::optional<weight_t const*> weights{thrust::nullopt};
     edge_t local_degree{};
     thrust::tie(indices, weights, local_degree) = matrix_partition.get_local_edges(major_offset);
     auto sum                                    = thrust::transform_reduce(
@@ -246,7 +246,7 @@ __global__ void for_all_major_for_all_nbr_mid_degree(
   while (idx < static_cast<size_t>(major_last - major_first)) {
     auto major_offset = major_start_offset + idx;
     vertex_t const* indices{nullptr};
-    thrust::optional<weight_t const*> weights{nullptr};
+    thrust::optional<weight_t const*> weights{thrust::nullopt};
     edge_t local_degree{};
     thrust::tie(indices, weights, local_degree) = matrix_partition.get_local_edges(major_offset);
     for (edge_t i = lane_id; i < local_degree; i += raft::warp_size()) {
@@ -317,7 +317,7 @@ __global__ void for_all_major_for_all_nbr_high_degree(
   while (idx < static_cast<size_t>(major_last - major_first)) {
     auto major_offset = major_start_offset + idx;
     vertex_t const* indices{nullptr};
-    thrust::optional<weight_t const*> weights{nullptr};
+    thrust::optional<weight_t const*> weights{thrust::nullopt};
     edge_t local_degree{};
     thrust::tie(indices, weights, local_degree) = matrix_partition.get_local_edges(major_offset);
     for (edge_t i = threadIdx.x; i < local_degree; i += blockDim.x) {

cpp/include/cugraph/prims/update_frontier_v_push_if_out_nbr.cuh

@@ -293,7 +293,7 @@ __global__ void for_all_frontier_row_for_all_nbr_hypersparse(
       auto row_offset = matrix_partition.get_major_offset_from_major_nocheck(row);
       auto row_idx    = row_start_offset + *row_hypersparse_idx;
       vertex_t const* indices{nullptr};
-      thrust::optional<weight_t const*> weights{nullptr};
+      thrust::optional<weight_t const*> weights{thrust::nullopt};
       edge_t local_out_degree{};
       thrust::tie(indices, weights, local_out_degree) = matrix_partition.get_local_edges(row_idx);
       for (edge_t i = 0; i < local_out_degree; ++i) {
@@ -360,7 +360,7 @@ __global__ void for_all_frontier_row_for_all_nbr_low_degree(
     }
     auto row_offset = matrix_partition.get_major_offset_from_major_nocheck(row);
     vertex_t const* indices{nullptr};
-    thrust::optional<weight_t const*> weights{nullptr};
+    thrust::optional<weight_t const*> weights{thrust::nullopt};
     edge_t local_out_degree{};
     thrust::tie(indices, weights, local_out_degree) = matrix_partition.get_local_edges(row_offset);
     for (edge_t i = 0; i < local_out_degree; ++i) {
@@ -428,7 +428,7 @@ __global__ void for_all_frontier_row_for_all_nbr_mid_degree(
     }
     auto row_offset = matrix_partition.get_major_offset_from_major_nocheck(row);
     vertex_t const* indices{nullptr};
-    thrust::optional<weight_t const*> weights{nullptr};
+    thrust::optional<weight_t const*> weights{thrust::nullopt};
     edge_t local_out_degree{};
     thrust::tie(indices, weights, local_out_degree) = matrix_partition.get_local_edges(row_offset);
     for (edge_t i = lane_id; i < local_out_degree; i += raft::warp_size()) {
@@ -494,7 +494,7 @@ __global__ void for_all_frontier_row_for_all_nbr_high_degree(
     }
     auto row_offset = matrix_partition.get_major_offset_from_major_nocheck(row);
     vertex_t const* indices{nullptr};
-    thrust::optional<weight_t const*> weights{nullptr};
+    thrust::optional<weight_t const*> weights{thrust::nullopt};
     edge_t local_out_degree{};
     thrust::tie(indices, weights, local_out_degree) = matrix_partition.get_local_edges(row_offset);
     for (edge_t i = threadIdx.x; i < local_out_degree; i += blockDim.x) {