[REVIEW] Biased Random Walks for GNN

cpp/include/cugraph/algorithms.hpp

@@ -1344,6 +1344,8 @@ extract_ego(raft::handle_t const& handle,
  * (compressed) format; when padding is used the output is a matrix of vertex paths and a matrix of
  * edges paths (weights); in this case the matrices are stored in row major order; the vertex path
  * matrix is padded with `num_vertices` values and the weight matrix is padded with `0` values;
+ * @param selector_type identifier for sampling strategy: uniform, biased, etc.; possible
+ * values{0==uniform, 1==biased}; defaults to 0 == uniform;
  * @return std::tuple<rmm::device_uvector<vertex_t>, rmm::device_uvector<weight_t>,
  * rmm::device_uvector<index_t>> Triplet of either padded or coalesced RW paths; in the coalesced
  * case (default), the return consists of corresponding vertex and edge weights for each, and
@@ -1363,7 +1365,8 @@ random_walks(raft::handle_t const& handle,
              typename graph_t::vertex_type const* ptr_d_start,
              index_t num_paths,
              index_t max_depth,
-             bool use_padding = false);
+             bool use_padding  = false,
+             int selector_type = 0);
 
 /**
  * @brief Finds (weakly-connected-)component IDs of each vertices in the input graph.

cpp/include/cugraph/graph.hpp

@@ -176,6 +176,29 @@ class graph_t<vertex_t, edge_t, weight_t, store_transposed, multi_gpu, std::enab
       false);
   }
 
+  // FIXME: possibley to be added later;
+  // for now it's unnecessary;
+  // (commented out, per reviewer request)
+  //
+  // generic in-place sorter on CSR structure;
+  // this is specifically targetting
+  // segmented-sort by weigths; but
+  // must be generic enough to support future
+  // types of sorting;
+  // Notes:
+  // (1.) criterion is mutable (non-const)
+  //      to allow for sorter obejcts for which
+  //      the sorting operation fills additional structures
+  //      (later to be retrieved; e.g., for debugging);
+  // (2.) sorting object is responsible for updating "in-place"
+  //      any of the (offsets, indices, weights) arrays;
+  //
+  // template <typename in_place_sorter_t>
+  // void sort(in_place_sorter_t& criterion)
+  // {
+  //   criterion(offsets_, indices_, weights_);
+  // }
+
  private:
   friend class cugraph::serializer::serializer_t;
 

cpp/src/sampling/random_walks.cu

@@ -30,7 +30,8 @@ template std::
                int32_t const* ptr_d_start,
                int32_t num_paths,
                int32_t max_depth,
-               bool use_padding);
+               bool use_padding,
+               int selector_type);
 
 template std::
   tuple<rmm::device_uvector<int32_t>, rmm::device_uvector<float>, rmm::device_uvector<int64_t>>
@@ -39,7 +40,8 @@ template std::
                int32_t const* ptr_d_start,
                int64_t num_paths,
                int64_t max_depth,
-               bool use_padding);
+               bool use_padding,
+               int selector_type);
 
 template std::
   tuple<rmm::device_uvector<int64_t>, rmm::device_uvector<float>, rmm::device_uvector<int64_t>>
@@ -48,7 +50,8 @@ template std::
                int64_t const* ptr_d_start,
                int64_t num_paths,
                int64_t max_depth,
-               bool use_padding);
+               bool use_padding,
+               int selector_type);
 //}
 //
 // SG FP64{
@@ -59,7 +62,8 @@ template std::
                int32_t const* ptr_d_start,
                int32_t num_paths,
                int32_t max_depth,
-               bool use_padding);
+               bool use_padding,
+               int selector_type);
 
 template std::
   tuple<rmm::device_uvector<int32_t>, rmm::device_uvector<double>, rmm::device_uvector<int64_t>>
@@ -68,7 +72,8 @@ template std::
                int32_t const* ptr_d_start,
                int64_t num_paths,
                int64_t max_depth,
-               bool use_padding);
+               bool use_padding,
+               int selector_type);
 
 template std::
   tuple<rmm::device_uvector<int64_t>, rmm::device_uvector<double>, rmm::device_uvector<int64_t>>
@@ -77,7 +82,8 @@ template std::
                int64_t const* ptr_d_start,
                int64_t num_paths,
                int64_t max_depth,
-               bool use_padding);
+               bool use_padding,
+               int selector_type);
 //}
 
 template std::