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  1. #include <mpi.h>
  2. #include <stdio.h>
  3. #include <stdlib.h>
  4. #include <unistd.h>
  5.  
  6. // size of array
  7. #define n 10
  8.  
  9. int a[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
  10.  
  11. // Temporary array for slave process
  12. int a2[1000];
  13.  
  14. int main(int argc, char* argv[])
  15. {
  16.  
  17.     int pid, np,elements_per_process,n_elements_recieved;
  18.     // np -> no. of processes
  19.     // pid -> process id
  20.  
  21.     MPI_Status status;
  22.  
  23.     // Creation of parallel processes
  24.     MPI_Init(&argc, &argv);
  25.  
  26.     // find out process ID,
  27.     // and how many processes were started
  28.     MPI_Comm_rank(MPI_COMM_WORLD, &pid);
  29.     MPI_Comm_size(MPI_COMM_WORLD, &np);
  30.  
  31.     // master process
  32.     if (pid == 0)
  33.     {
  34.         int index,i;
  35.         elements_per_process = n / np;
  36.  
  37.         // check if more than 1 processes are run
  38.         if (np > 1)
  39.         {
  40.             // distributes the portion of array
  41.             // to child processes to calculate
  42.             // their partial sums
  43.             for (i = 1; i < np - 1; i++)
  44.             {
  45.                 index = i * elements_per_process;
  46.  
  47.                 MPI_Send(&elements_per_process,1, MPI_INT, i, 0,MPI_COMM_WORLD);
  48.                 MPI_Send(&a[index],elements_per_process,MPI_INT, i, 0,MPI_COMM_WORLD);
  49.             }
  50.  
  51.             // last process adds remaining elements
  52.             index = i * elements_per_process;
  53.             int elements_left = n - index;
  54.  
  55.             MPI_Send(&elements_left,1, MPI_INT,i, 0,MPI_COMM_WORLD);
  56.             MPI_Send(&a[index],elements_left,MPI_INT, i, 0,MPI_COMM_WORLD);
  57.        }
  58.  
  59.         // master process add its own sub array
  60.         int sum = 0;
  61.  
  62.         for (i = 0; i < elements_per_process; i++)
  63.             sum += a[i];
  64.  
  65.         // collects partial sums from other processes
  66.         int tmp;
  67.  
  68.         for (i = 1; i < np; i++) 
  69.         {
  70.             MPI_Recv(&tmp, 1, MPI_INT,MPI_ANY_SOURCE, 0,MPI_COMM_WORLD,&status);
  71.  
  72.             int sender = status.MPI_SOURCE;
  73.  	     sum += tmp;
  74.         }
  75.  
  76.         // prints the final sum of array
  77.         printf("Sum of array is : %d\n", sum);
  78.     }
  79.  
  80.     // slave processes
  81.     else
  82.     {
  83.         MPI_Recv(&n_elements_recieved,1, MPI_INT, 0, 0,MPI_COMM_WORLD,&status);
  84.  
  85.         // stores the received array segment
  86.         // in local array a2
  87.         MPI_Recv(&a2, n_elements_recieved,MPI_INT, 0, 0,MPI_COMM_WORLD,&status);
  88.  
  89.         // calculates its partial sum
  90.         int partial_sum = 0;
  91.  
  92.         for (int i = 0; i < n_elements_recieved; i++)
  93.             partial_sum += a2[i];
  94.  
  95.         // sends the partial sum to the root process
  96.         MPI_Send(&partial_sum, 1, MPI_INT,0, 0, MPI_COMM_WORLD);
  97.     }
  98.  
  99.     // cleans up all MPI state before exit of process
  100.     MPI_Finalize();
  101.  
  102.     return 0;
  103. }
  104.  
Success #stdin #stdout #stderr 0.28s 40692KB
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Standard input is empty
stdout
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Standard output is empty
stderr
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Error: unexpected '/' in "/"
Execution halted
https://ideone.com/f2DUvH
language:
R (R 3.5.2)
created:
16 days ago
visibility:
public

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