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  1. #include <mpi.h>
  2. #include <stdio.h>
  3. #include <stdlib.h>
  4.  
  5. int main(int argc, char *argv[]) {
  6.     int errs = 0;
  7.     int rank, size;
  8.     long long int N, local_sum = 0, global_sum = 0;
  9.  
  10.     MPI_Init(&argc, &argv);
  11.     MPI_Comm_rank(MPI_COMM_WORLD, &rank);
  12.     MPI_Comm_size(MPI_COMM_WORLD, &size);
  13.  
  14.     if (argc < 2) {
  15.         printf("Usage: %s <N>\n", argv[0]);
  16.         MPI_Abort(MPI_COMM_WORLD, 1);
  17.     }
  18.  
  19.     N = atoll(argv[1]);
  20.  
  21.     // Calculate local sum
  22.     long long int start = (N / size) * rank;
  23.     long long int end = start + N / size;
  24.     if (rank == size - 1) {
  25.         end = N;
  26.     }
  27.     for (long long int i = start; i < end; i++) {
  28.         local_sum += i;
  29.     }
  30.  
  31.     // Perform reduction to compute global sum
  32.     MPI_Reduce(&local_sum, &global_sum, 1, MPI_LONG_LONG, MPI_SUM, 0, MPI_COMM_WORLD);
  33.  
  34.     // Print result
  35.     if (rank == 0) {
  36.         printf("Sum from 0 to %lld is %lld\n", N, global_sum);
  37.     }
  38.  
  39.     MPI_Finalize();
  40.     return errs;
  41. }
  42.  
Success #stdin #stdout #stderr 0.29s 40724KB
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Standard input is empty
stdout
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Standard output is empty
stderr
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Error: unexpected symbol in "int main"
Execution halted
https://ideone.com/775jhD
language:
R (R 3.5.2)
created:
19 days ago
visibility:
public

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