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Boost.MPI: What happened is not what was sent!

I am relatively new to using Boost MPI. I have installed libraries, compiling the code, but I get a very strange error - some integer data received by the sub-nodes is not what was sent by the wizard. What's happening?

I am using boost version 1.42.0, compiling code using mpiC ++ (which wraps g ++ on one cluster and icpc on another). The following is an example, including output.

the code:

#include <iostream>
#include <boost/mpi.hpp>

using namespace std;
namespace mpi = boost::mpi;

class Solution
{
public:
  Solution() :
  solution_num(num_solutions++)
  {
    // Master node constructor
  }

  Solution(int solutionNum) :
  solution_num(solutionNum)
  {
    // Slave nodes' constructor.
  }

  int solutionNum() const
  {
    return solution_num;
  }

private:
  static int num_solutions;
  int solution_num;
};

int Solution::num_solutions = 0;

int main(int argc, char* argv[])
{
  // Initialization of MPI
  mpi::environment env(argc, argv);
  mpi::communicator world;

  if (world.rank() == 0)
  {
    // Create solutions
    int numSolutions = world.size() - 1;  // One solution per slave
    vector<Solution*> solutions(numSolutions);
    for (int sol = 0; sol < numSolutions; ++sol)
    {
      solutions[sol] = new Solution;
    }

    // Send solutions
    for (int sol = 0; sol < numSolutions; ++sol)
    {
      world.isend(sol + 1, 0, false);  // Tells the slave to expect work
      cout << "Sending solution no. " << solutions[sol]->solutionNum() << " to node " << sol + 1 << endl;
      world.isend(sol + 1, 1, solutions[sol]->solutionNum());
    }

    // Retrieve values (solution numbers squared)
    vector<double> values(numSolutions, 0);
    for (int i = 0; i < numSolutions; ++i)
    {
      // Get values for each solution
      double value = 0;
      mpi::status status = world.recv(mpi::any_source, 2, value);
      int source = status.source();

      int sol = source - 1;
      values[sol] = value;
    }
    for (int i = 1; i <= numSolutions; ++i)
    {
      world.isend(i, 0, true);  // Tells the slave to finish
    }

    // Output the solutions numbers and their squares
    for (int i = 0; i < numSolutions; ++i)
    {
      cout << solutions[i]->solutionNum() << ", " << values[i] << endl;
      delete solutions[i];
    }
  }
  else
  {
    // Slave nodes merely square the solution number
    bool finished;
    mpi::status status = world.recv(0, 0, finished);
    while (!finished)
    {
      int solNum;
      world.recv(0, 1, solNum);
      cout << "Node " << world.rank() << " receiving solution no. " << solNum << endl;

      Solution solution(solNum);
      double value = static_cast<double>(solNum * solNum);
      world.send(0, 2, value);

      status = world.recv(0, 0, finished);
    }

    cout << "Node " << world.rank() << " finished." << endl;
  }

  return EXIT_SUCCESS;
}

Running this on 21 nodes (1 master, 20 subordinates) produces:

Sending solution no. 0 to node 1
Sending solution no. 1 to node 2
Sending solution no. 2 to node 3
Sending solution no. 3 to node 4
Sending solution no. 4 to node 5
Sending solution no. 5 to node 6
Sending solution no. 6 to node 7
Sending solution no. 7 to node 8
Sending solution no. 8 to node 9
Sending solution no. 9 to node 10
Sending solution no. 10 to node 11
Sending solution no. 11 to node 12
Sending solution no. 12 to node 13
Sending solution no. 13 to node 14
Sending solution no. 14 to node 15
Sending solution no. 15 to node 16
Sending solution no. 16 to node 17
Sending solution no. 17 to node 18
Sending solution no. 18 to node 19
Sending solution no. 19 to node 20
Node 1 receiving solution no. 0
Node 2 receiving solution no. 1
Node 12 receiving solution no. 19
Node 3 receiving solution no. 19
Node 15 receiving solution no. 19
Node 13 receiving solution no. 19
Node 4 receiving solution no. 19
Node 9 receiving solution no. 19
Node 10 receiving solution no. 19
Node 14 receiving solution no. 19
Node 6 receiving solution no. 19
Node 5 receiving solution no. 19
Node 11 receiving solution no. 19
Node 8 receiving solution no. 19
Node 16 receiving solution no. 19
Node 19 receiving solution no. 19
Node 20 receiving solution no. 19
Node 1 finished.
Node 2 finished.
Node 7 receiving solution no. 19
0, 0
1, 1
2, 361
3, 361
4, 361
5, 361
6, 361
7, 361
8, 361
9, 361
10, 361
11, 361
12, 361
13, 361
14, 361
15, 361
16, 361
17, 361
18, 361
19, 361
Node 6 finished.
Node 3 finished.
Node 17 receiving solution no. 19
Node 17 finished.
Node 10 finished.
Node 12 finished.
Node 8 finished.
Node 4 finished.
Node 15 finished.
Node 18 receiving solution no. 19
Node 18 finished.
Node 11 finished.
Node 13 finished.
Node 20 finished.
Node 16 finished.
Node 9 finished.
Node 19 finished.
Node 7 finished.
Node 5 finished.
Node 14 finished.

, 0 node 1, 1 node 2, 2 node 3 .., ( ) 19. , 0 19, 0, 1 19 18 !

, .

+3
4

, , , MPI C. Boost "isend" "MPI_Isend", , "MPI_Isend".

"MPI_Isend" - , , . , , , , . :

// Get solution numbers from the solutions and store in a vector
vector<int> solutionNums(numSolutions);
for (int sol = 0; sol < numSolutions; ++sol)
{
  solutionNums[sol] = solutions[sol]->solutionNum();
}

// Send solution numbers
for (int sol = 0; sol < numSolutions; ++sol)
{
  world.isend(sol + 1, 0, false);  // Indicates that we have not finished, and to expect a solution representation
  cout << "Sending solution no. " << solutionNums[sol] << " to node " << sol + 1 << endl;
  world.isend(sol + 1, 1, solutionNums[sol]);
}

, . :

// Create solutionNum array
vector<int> solutionNums(numSolutions);
for (int sol = 0; sol < numSolutions; ++sol)
{
  solutionNums[sol] = solutions[sol]->solutionNum();
}

// Send solutions
for (int sol = 0; sol < numSolutions; ++sol)
{
  int solNum = solutionNums[sol];
  world.isend(sol + 1, 0, false);  // Indicates that we have not finished, and to expect a solution representation
  cout << "Sending solution no. " << solNum << " to node " << sol + 1 << endl;
  world.isend(sol + 1, 1, solNum);
}

"MPI_Isend" solNum. , , , , 4 node 5, (19 ).

:

// Send solutions
for (int sol = 0; sol < numSolutions; ++sol)
{
  world.isend(sol + 1, 0, false);  // Tells the slave to expect work
  cout << "Sending solution no. " << solutions[sol]->solutionNum() << " to node " << sol + 1 << endl;
  world.isend(sol + 1, 1, solutions[sol]->solutionNum());
}

. , . , .

, "" , "send" "isend" . , "isend" , !

+11

, . , () . mpi::request isend. communicator::isend_impl(int dest, int tag, const T& value, mpl::false_) communicator.hpp boost, , . , - .

: isend!

+4

" [sol] = "; , num_solution ++. , , , .

, , 20 numsolutions ++ 20 _num = num_solutions ctor- (), , .

for (int sol = 0; sol < numSolutions; ++sol)
    {
      solutions[sol] = new Solution;
    }


for (int sol = 0; sol < numSolutions; ++sol)
    {
      solutions[sol] = new Solution(sol);
    }

. , , - , , - 20 .

+2

milianw: , isend - , , , test() wait() isend. , isend() . {test, wait} _ {any, some, all}.

- , , , MPI. , .

+1

Source: https://habr.com/ru/post/1771523/

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