termination.c

   1 /*
   2   Parallel Programming - 2026/2027
   3
   4   The main program
   5 */
   6
   7 #include <mpi.h>
   8 #include <pthread.h>
   9
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <unistd.h>
  13 #include <string.h>
  14
  15 #include "global.h"
  16 #include "basic.h"
  17 #include "control.h"
  18 #include "util.h"
  19
  20 /*
  21   Main program:
  22
  23   - Initialise the MPI environment.
  24   - Process command line arguments.
  25   - Start the basic algorithm thread.
  26   - Start the control algorithm (termination detection) thread.
  27   - Wait for the control algorithm to terminate, signalling that the
  28     terminatation of the basic algorithm has been detected.
  29   - Cancel the basic algorithm thread.
  30 */
  31 int main(int argc, char *argv[])
  32 {
  33   // process data
  34   int rank, processes;
  35
  36   int mpi_threads_support;
  37
  38   // initialise MPI framework
  39   MPI_Init_thread(&argc, &argv, MPI_THREAD_MULTIPLE, &mpi_threads_support);
  40
  41   MPI_Comm_rank(MPI_COMM_WORLD, &rank);         // get process id
  42   MPI_Comm_size(MPI_COMM_WORLD, &processes);    // get number of processes
  43
  44   if (mpi_threads_support < MPI_THREAD_MULTIPLE && rank == 0)
  45     warn("%s: warning: threads not fully supported\n", argv[0]);
  46
  47   if (processes < 2)
  48     warn("%s: warning: there must be at least 2 processes\n", argv[0]);
  49
  50   // parse arguments
  51   int arg = 1;
  52
  53   while (arg < argc)
  54     {
  55       // parse one argument
  56       if (strcmp(argv[arg], "--quiet") == 0)
  57         {
  58           // silence debugging messages
  59           QUIET = 1;
  60         }
  61       else if (strcmp(argv[arg], "-r") == 0)
  62         {
  63           // re-seed random number generator
  64           srand(time(0));
  65         }
  66       else
  67         warn("%s: unknown option `%s'\n", argv[0]);
  68
  69       arg++;
  70     }
  71
  72   // give all the processes a chance to start
  73   MPI_Barrier(MPI_COMM_WORLD);
  74
  75   // the program
  76   if (rank == 0)
  77     printf("Starting basic algorithm\n");
  78
  79   // arguments for the basic and the control algorithms
  80   thread_args_t threads_args = { rank, processes, rank == 0 };
  81
  82   // start basic algorithm thread
  83   pthread_t basic_thread;
  84
  85   if (pthread_create(&basic_thread, NULL, basic_algorithm, &threads_args) != 0)
  86     {
  87       perror("pthread_create (basic)");
  88
  89       return 1;
  90     }
  91
  92   // start control thread
  93   pthread_t control_thread;
  94
  95   if (pthread_create(&control_thread, NULL, detect_termination, &threads_args) != 0)
  96     {
  97       perror("pthread_create (control)");
  98
  99       return 2;
 100     }
 101
 102   // wait for control thread to end
 103   pthread_join(control_thread, NULL);
 104
 105   // stop (terminated) basic algorithm thread
 106   pthread_cancel(basic_thread);
 107   pthread_join(basic_thread, NULL);
 108
 109   // wrap up
 110   MPI_Finalize();
 111
 112   if (rank == 0)
 113     printf("Terminating\n");
 114
 115   return 0;
 116 }