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57 lines
2.5 KiB
C++
57 lines
2.5 KiB
C++
#include <mpi.h>
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#include <iostream>
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/*
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MPI_Send(
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void* data, //data buffer
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int count, //count of elements
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MPI_Datatype datatype, //type of element
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int destination, //rank of receiver
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int tag, //tag of message
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MPI_Comm communicator //communicator
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)
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MPI_Recv(
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void* data, //data buffer
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int count, //count of elements
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MPI_Datatype datatype, //type of element
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int source, //rank of receiver
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int tag, //tag of message
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MPI_Comm communicator, //communicator
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MPI_Status* status //about received message
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)
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*/
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int main(int argc, char* argv[])
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{
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MPI_Init(NULL, NULL); //Initialize the MPI environment
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int world_size;
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MPI_Comm_size(MPI_COMM_WORLD, &world_size); //Get the number of processes
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int world_rank;
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MPI_Comm_rank(MPI_COMM_WORLD, &world_rank); //Get the number of process
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long long token;
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if (world_rank != 0)
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{
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// MPI_Recv(data, count, datatype, source, tag, communicator, status)
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MPI_Recv(&token, 1, MPI_LONG_LONG, world_rank-1, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE); //We use MPI_Recv to force not 0 process to wait the token, this because the function is blocking
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std::cout << "Process (rank " << world_rank+1 << "/" << world_size << ") received '" << token << "' from " << world_rank << std::endl;
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}
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else
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token = 19; //Setup the token value if im processor 0
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// MPI_Send(data, count, datatype, dest, tag, communicator)
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MPI_Send(&token, 1, MPI_LONG_LONG, (world_rank+1)%world_size, 0, MPI_COMM_WORLD); //As first time for process 0, each process after getting the token, send it to the next(+1) process
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//Make process 0 finally get able to retrieve his token after passing it
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if (world_rank == 0)
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{
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// MPI_Recv(data, count, datatype, source, tag, communicator, status)
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MPI_Recv(&token, 1, MPI_LONG_LONG, (world_rank-1)%world_size, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE); //To recive the last Send token before ending
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std::cout << "Process (rank " << world_rank+1 << "/" << world_size << ") received '" << token << "' from " << (world_rank)%world_size << std::endl;
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}
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MPI_Finalize(); //Clean up the MPI environment
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return 0;
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} |