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44 | /*
* Copyright 2021 Jeisson Hidalgo-Cespedes - Universidad de Costa Rica
* Creates a secondary thread that greets in the standard output
*/
#include <mpi.h>
#include <cstdint>
#include <iostream>
int main(int argc, char* argv[]) {
if (MPI_Init(&argc, &argv) == MPI_SUCCESS) {
int my_rank = -1;
MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
int process_count = -1;
MPI_Comm_size(MPI_COMM_WORLD, &process_count);
char hostname[MPI_MAX_PROCESSOR_NAME];
int hostname_len = -1;
MPI_Get_processor_name(hostname, &hostname_len);
const int32_t previous = (process_count + my_rank - 1) % process_count;
const int32_t next = (my_rank + 1) % process_count;
int32_t can_print = 1;
if (my_rank != 0) {
MPI_Recv(&can_print, /*capacity*/ 1, MPI_INT32_T, /*source*/previous
, /*tag*/ 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
}
std::cout << "Hello from main thread of process " << my_rank
<< " of " << process_count << " on " << hostname << std::endl;
if (my_rank < process_count - 1) {
MPI_Send(&can_print, /*count*/ 1, MPI_INT32_T, /*dest*/ next, /*tag*/ 0
, MPI_COMM_WORLD);
}
MPI_Finalize();
} else {
std::cout << "Error: could not init MPI environment" << std::endl;
}
return 0;
}
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