util.c

   1 /*
   2   Parallel Programming - 2026/2027
   3
   4   Utility functions
   5 */
   6
   7 #include <stdio.h>
   8 #include <stdarg.h>
   9 #include <stdlib.h>
  10 #include <time.h>
  11
  12
  13 // controls the output of debugging messages, set to 1 to have no
  14 // messages
  15 int QUIET = 0;
  16
  17
  18 // returns a random integer in [A,B]
  19 int rand_ab(int a, int b)
  20 {
  21   return a + rand() % (b - a + 1);
  22 }
  23
  24 // sleep between MIN and MAX ms
  25 void rand_sleep(int min, int max)
  26 {
  27   int ms = rand_ab(min, max);
  28   struct timespec ts = { ms / 1000, (ms % 1000) * 1000 };
  29
  30   nanosleep(&ts, NULL);
  31 }
  32
  33 // output a debugging message to stderr
  34 void trace(char *format, ...)
  35 {
  36   va_list args;
  37
  38   if (QUIET)
  39     return;
  40
  41   va_start (args, format);
  42   vfprintf(stderr, format, args);
  43   va_end (args);
  44 }
  45
  46 // unconditionally output a message to stderr
  47 void warn(char *format, ...)
  48 {
  49   va_list args;
  50
  51   va_start (args, format);
  52   vfprintf(stderr, format, args);
  53   va_end (args);
  54 }
  55
  56 /*
  57   Evaluates Rule C & D of Dijkstra-Scholten. Caller must already hold state_mutex!
  58 */
  59 static void try_resolve_tree(int my_id)
  60 {
  61     if (state == PASSIVE_STATE && deficit == 0)
  62     {
  63         if (is_initiator) {
  64             // Root is passive and deficit is 0 -> Global Termination!
  65             return;
  66         }
  67
  68         if (parent != -1)
  69         {
  70             control_message_t sig = {0};
  71             // Send acknowledgment signal up the tree to our parent
  72             MPI_Send(&sig, sizeof(control_message_t), MPI_BYTE, parent,
  73                      CONTROL_SIGNAL, MPI_COMM_WORLD);
  74
  75             trace("%d: [CONTROL] Sent tree-signal to parent %d\n", my_id, parent);
  76             parent = -1; // Detach from tree
  77
  78         }
  79     }
  80 }