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  1. #include <mpi.h>
  2. #include <stdio.h>
  3. #include <stdlib.h>
  4. #include <math.h>
  5.  
  6. // Function to check if a number is prime
  7. int is_prime(int num) {
  8.     if (num <= 1) return 0; // 0 and 1 are not prime
  9.     if (num <= 3) return 1; // 2 and 3 are prime
  10.     if (num % 2 == 0 || num % 3 == 0) return 0; // eliminate even numbers and multiples of 3
  11.     for (int i = 5; i <= sqrt(num); i += 6) {
  12.         if (num % i == 0 || num % (i + 2) == 0) return 0;
  13.     }
  14.     return 1;
  15. }
  16.  
  17. int main(int argc, char** argv) {
  18.     int rank, size;
  19.     int lower, upper;
  20.  
  21.     // Initialize MPI
  22.     MPI_Init(&argc, &argv);
  23.     MPI_Comm_rank(MPI_COMM_WORLD, &rank);
  24.     MPI_Comm_size(MPI_COMM_WORLD, &size);
  25.  
  26.     // Read the range of numbers from the user (only by the master process)
  27.     if (rank == 0) {
  28.         printf("Enter the lower bound of the range: ");
  29.         scanf("%d", &lower);
  30.         printf("Enter the upper bound of the range: ");
  31.         scanf("%d", &upper);
  32.     }
  33.  
  34.     // Broadcast the range to all processes
  35.     MPI_Bcast(&lower, 1, MPI_INT, 0, MPI_COMM_WORLD);
  36.     MPI_Bcast(&upper, 1, MPI_INT, 0, MPI_COMM_WORLD);
  37.  
  38.     // Calculate the range of numbers for each process
  39.     int range = upper - lower + 1;
  40.     int local_lower = lower + (rank * range / size);
  41.     int local_upper = lower + ((rank + 1) * range / size) - 1;
  42.  
  43.     // Find primes in the assigned range
  44.     int* local_primes = malloc((local_upper - local_lower + 1) * sizeof(int));
  45.     int local_count = 0;
  46.  
  47.     for (int i = local_lower; i <= local_upper; i++) {
  48.         if (is_prime(i)) {
  49.             local_primes[local_count++] = i;
  50.         }
  51.     }
  52.  
  53.     // Gather prime counts from all processes
  54.     int* recv_counts = NULL;
  55.     if (rank == 0) {
  56.         recv_counts = malloc(size * sizeof(int));
  57.     }
  58.     MPI_Gather(&local_count, 1, MPI_INT, recv_counts, 1, MPI_INT, 0, MPI_COMM_WORLD);
  59.  
  60.     // Gather all primes from all processes
  61.     int* displacements = NULL;
  62.     int total_primes = 0;
  63.     if (rank == 0) {
  64.         displacements = malloc(size * sizeof(int));
  65.         displacements[0] = 0;
  66.         for (int i = 1; i < size; i++) {
  67.             displacements[i] = displacements[i - 1] + recv_counts[i - 1];
  68.         }
  69.         total_primes = displacements[size - 1] + recv_counts[size - 1];
  70.     }
  71.  
  72.     int* global_primes = NULL;
  73.     if (rank == 0) {
  74.         global_primes = malloc(total_primes * sizeof(int));
  75.     }
  76.     MPI_Gatherv(local_primes, local_count, MPI_INT, global_primes, recv_counts, displacements, MPI_INT, 0, MPI_COMM_WORLD);
  77.  
  78.     // Print the result
  79.     if (rank == 0) {
  80.         printf("Prime numbers in the range [%d, %d]:\n", lower, upper);
  81.         for (int i = 0; i < total_primes; i++) {
  82.             printf("%d ", global_primes[i]);
  83.         }
  84.         printf("\n");
  85.  
  86.         // Free dynamically allocated memory
  87.         free(global_primes);
  88.         free(recv_counts);
  89.         free(displacements);
  90.     }
  91.  
  92.     // Finalize MPI and free local memory
  93.     free(local_primes);
  94.     MPI_Finalize();
  95.  
  96.     return 0;
  97. }
  98.  
Success #stdin #stdout #stderr 0.29s 40104KB
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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/njwSju
language:
R (R 3.5.2)
created:
297 days ago
visibility:
public

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