[GitHub] BullDemonKing commented on a change in pull request #13588: Accelerate DGL csr neighbor sampling

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BullDemonKing commented on a change in pull request #13588: Accelerate DGL csr neighbor sampling
URL: https://github.com/apache/incubator-mxnet/pull/13588#discussion_r242011871
 
 

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 File path: src/operator/contrib/dgl_graph.cc
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 @@ -586,123 +563,119 @@ static void SampleSubgraph(const NDArray &csr,
   dgl_id_t* out_layer = sub_layer.data().dptr<dgl_id_t>();
 
   // BFS traverse the graph and sample vertices
-  dgl_id_t sub_vertices_count = 0;
   // <vertex_id, layer_id>
-  std::unordered_map<dgl_id_t, int> sub_ver_mp;
-  std::queue<ver_node> node_queue;
+  std::unordered_set<dgl_id_t> sub_ver_mp;
+  std::vector<std::pair<dgl_id_t, dgl_id_t> > sub_vers;
+  sub_vers.reserve(num_seeds * 10);
 
 Review comment:
   This number is used for reserving memory, so it doesn't have to be very accurate. The goal here is to balance memory reallocation and memory consumption in std::vector. If num_hop is 1, 10 might be good enough; if num_hop is 2, 10 will be too small. But I don't feel that we need to make it overcomplex. After all, we only want to reduce the overhead of memory reallocation in std::vector.

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