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  1. #include <mpi.h>
  2. #include <stdio.h>
  3.  
  4. int main(int argc, char** argv) {
  5.     int rank, size;
  6.     int I = 1; // Starting value
  7.     int p = 10; // Ending value (inclusive)
  8.     int local_value, global_sum;
  9.  
  10.     // Initialize MPI
  11.     MPI_Init(&argc, &argv);
  12.     MPI_Comm_rank(MPI_COMM_WORLD, &rank);
  13.     MPI_Comm_size(MPI_COMM_WORLD, &size);
  14.  
  15.     // Assign values to processes
  16.     local_value = rank + I;
  17.  
  18.     // Perform sum reduction
  19.     MPI_Reduce(&local_value, &global_sum, 1, MPI_INT, MPI_SUM, 0, MPI_COMM_WORLD);
  20.  
  21.     // Process 0 computes and prints the result
  22.     if (rank == 0) {
  23.         printf("Sum computed by reduction: %d\n", global_sum);
  24.  
  25.         // Compute the expected sum using the formula p(p+1)/2
  26.         int expected_sum = p * (p + 1) / 2;
  27.         printf("Expected sum using formula p(p+1)/2: %d\n", expected_sum);
  28.  
  29.         // Double-check the values match
  30.         if (global_sum == expected_sum) {
  31.             printf("The computed sum matches the expected sum.\n");
  32.         } else {
  33.             printf("The computed sum does not match the expected sum!\n");
  34.         }
  35.     }
  36.  
  37.     // Finalize MPI
  38.     MPI_Finalize();
  39.     return 0;
  40. }
  41.  
Success #stdin #stdout #stderr 0.31s 40700KB
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Standard input is empty
stdout
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Standard output is empty
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Error: unexpected symbol in "int main"
Execution halted
https://ideone.com/q7vcyb
language:
R (R 3.5.2)
created:
5 days ago
visibility:
public

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