# Memory requirement estimate for a large graph

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## Memory requirement estimate for a large graph

 Dear Tiago,How is it possible to get an estimate for the memory requirement of a graph in graph-tool?I know that graph-tool is built upon C++ and Boost, and the adjacency list is stored via a hash-map.Apart from the cost of storing the values of vertices indices and edges indices as `unsigned long`, what is the memory overhead of the structures used in storing the graph?For example, for a network of 1M vertices and 100M links without attributes, how much real memory should I plan to use, excluding temporaries?Sorry if the question is repeated, but I could not find it in the previous mailing list posts.Regards,Carlo _______________________________________________ graph-tool mailing list [hidden email] https://lists.skewed.de/mailman/listinfo/graph-tool
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## Re: Memory requirement estimate for a large graph

 Administrator Am 06.07.20 um 13:00 schrieb Carlo Nicolini: > Dear Tiago, > > How is it possible to get an estimate for the memory requirement of a > graph in graph-tool? Yes, it is, and I should put this in the documentation somewhere. > I know that graph-tool is built upon C++ and Boost, and the adjacency > list is stored via a hash-map. Not quite, we use an adjacency list using std::vector<>. > Apart from the cost of storing the values of vertices indices and edges > indices as `unsigned long`, what is the memory overhead of the > structures used in storing the graph? We use a vector-based bidirectional adjacency list, so each edge appears twice. Each edge is comprised of two size_t (uint64_t) values, for the target/source and the edge index, so we need 32 bytes per edge. For each vertex we need a std::vector<> which is 24 bytes and a uint64_t to separate the in-/out-lists, so we also need 32 bytes per node. Therefore we need in total:     (N + E) * 32 bytes > For example, for a network of 1M vertices and 100M links without > attributes, how much real memory should I plan to use, excluding > temporaries? That would be:    3232000000 bytes = 3.01 GB In practice you will need a little more, since std::vector<> tends to over-commit. Best, Tiago -- Tiago de Paula Peixoto <[hidden email]> _______________________________________________ graph-tool mailing list [hidden email] https://lists.skewed.de/mailman/listinfo/graph-tool signature.asc (849 bytes) Download Attachment -- Tiago de Paula Peixoto