C++; MPI: Send struct with vector of vectors through MPI

Question

I'm trying to send this structure through MPI, but I don't know if that's right.

struct Node {
int sum_node;
int depth_node;
vector<vector<int> > subset;
vector<int> sum_subset;
vector<int> depth_subset;
};

Sending like this:

Node zz = stack.back();
stack.pop_back();
MPI_Send(&zz, sizeof(struct Node), MPI_BYTE, 1, MSG_WORK_SENT, MPI_COMM_WORLD);

Receiving like this:

Node gg;
MPI_Recv(&gg, sizeof(struct Node), MPI_BYTE, status.MPI_SOURCE, MSG_WORK_SENT, MPI_COMM_WORLD, &status);
stack.push_back(gg);

And program terminated with Segmentation fault. Can anyone help me, please?

Remember that internally, std::vector will have a pointer to a chunk of memory that will lie outside of a Node instance. — Rook
– Rook, Commented Nov 2, 2012 at 12:22

billz · Accepted Answer · 2012-11-02 11:48:09Z

4

You are sending non-POD data over MPI which is not correct. You need to serialize/deserialize the whole Node during send/receive work.

For example, if I have a node and I have 1000 elements in its sum_subset, now you only send sizeof(Node) over:

  Node d;
  for(int i=0;i<1000;i++)
  {
    d.sum_subset.push_back(1);
  }
  cout << sizeof(Node) << endl;

answered Nov 2, 2012 at 10:28

billz

45.6k9 gold badges87 silver badges103 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Thank you, I will have to serialize my struct. I will do it into vector which I should send through MPI.

«You are sending non-POD data over MPI which is not correct» You mean that although sending a vector<int> works, it's not correct?