[GraphBolt] Optimize hetero sampling on CPU (#7360)

graphbolt/include/graphbolt/fused_csc_sampling_graph.h

@@ -415,6 +415,13 @@ class FusedCSCSamplingGraph : public torch::CustomClassHolder {
  private:
   template <typename NumPickFn, typename PickFn>
   c10::intrusive_ptr<FusedSampledSubgraph> SampleNeighborsImpl(
+      const torch::Tensor& seeds,
+      torch::optional<std::vector<int64_t>>& seed_offsets,
+      const std::vector<int64_t>& fanouts, bool return_eids,
+      NumPickFn num_pick_fn, PickFn pick_fn) const;
+
+  template <typename NumPickFn, typename PickFn>
+  c10::intrusive_ptr<FusedSampledSubgraph> TemporalSampleNeighborsImpl(
       const torch::Tensor& nodes, bool return_eids, NumPickFn num_pick_fn,
       PickFn pick_fn) const;
 
@@ -498,13 +505,14 @@ class FusedCSCSamplingGraph : public torch::CustomClassHolder {
  * @param offset The starting edge ID for the connected neighbors of the given
  * node.
  * @param num_neighbors The number of neighbors of this node.
- *
- * @return The pick number of the given node.
+ * @param num_picked_ptr The pointer of the tensor which stores the pick
+ * numbers.
  */
-int64_t NumPick(
+template <typename PickedNumType>
+void NumPick(
     int64_t fanout, bool replace,
     const torch::optional<torch::Tensor>& probs_or_mask, int64_t offset,
-    int64_t num_neighbors);
+    int64_t num_neighbors, PickedNumType* num_picked_ptr);
 
 int64_t TemporalNumPick(
     torch::Tensor seed_timestamp, torch::Tensor csc_indics, int64_t fanout,
@@ -513,11 +521,13 @@ int64_t TemporalNumPick(
     const torch::optional<torch::Tensor>& edge_timestamp, int64_t seed_offset,
     int64_t offset, int64_t num_neighbors);
 
-int64_t NumPickByEtype(
-    const std::vector<int64_t>& fanouts, bool replace,
+template <typename PickedNumType>
+void NumPickByEtype(
+    bool with_seed_offsets, const std::vector<int64_t>& fanouts, bool replace,
     const torch::Tensor& type_per_edge,
     const torch::optional<torch::Tensor>& probs_or_mask, int64_t offset,
-    int64_t num_neighbors);
+    int64_t num_neighbors, PickedNumType* num_picked_ptr, int64_t seed_index,
+    const std::vector<int64_t>& etype_id_to_num_picked_offset);
 
 int64_t TemporalNumPickByEtype(
     torch::Tensor seed_timestamp, torch::Tensor csc_indices,
@@ -610,16 +620,24 @@ int64_t TemporalPick(
  * probabilities associated with each neighboring edge of a node in the original
  * graph. It must be a 1D floating-point tensor with the number of elements
  * equal to the number of edges in the graph.
- * @param picked_data_ptr The destination address where the picked neighbors
+ * @param picked_data_ptr The pointer of the tensor where the picked neighbors
  * should be put. Enough memory space should be allocated in advance.
+ * @param seed_offset The offset(index) of the seed among the group of seeds
+ * which share the same node type.
+ * @param subgraph_indptr_ptr The pointer of the tensor which stores the indptr
+ * of the sampled subgraph.
+ * @param etype_id_to_num_picked_offset A vector storing the mappings from each
+ * etype_id to the offset of its pick numbers in the tensor.
  */
 template <SamplerType S, typename PickedType>
 int64_t PickByEtype(
-    int64_t offset, int64_t num_neighbors, const std::vector<int64_t>& fanouts,
-    bool replace, const torch::TensorOptions& options,
-    const torch::Tensor& type_per_edge,
+    bool with_seed_offsets, int64_t offset, int64_t num_neighbors,
+    const std::vector<int64_t>& fanouts, bool replace,
+    const torch::TensorOptions& options, const torch::Tensor& type_per_edge,
     const torch::optional<torch::Tensor>& probs_or_mask, SamplerArgs<S> args,
-    PickedType* picked_data_ptr);
+    PickedType* picked_data_ptr, int64_t seed_offset,
+    PickedType* subgraph_indptr_ptr,
+    const std::vector<int64_t>& etype_id_to_num_picked_offset);
 
 template <typename PickedType>
 int64_t TemporalPickByEtype(