/* illustrate token ring synchronization */
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include "pvm3.h"
#define TOKEN -9
#define NPROC 16
#define GROUP "thisRing"

void dowork(int,int);
void bail(int*, int, int);

int main(int argc, char**argv){
  int n, mytid, tids[NPROC - 1], me; 
  mytid = pvm_mytid();
  /* Join a group and if I am the first instance     */
  /* i.e. me = 0 spawn more copies of myself         */
  me = pvm_joingroup(GROUP);
  fprintf(stderr, "me = %d mytid = %d\n", me, mytid);
  if(me == 0){
    n = pvm_spawn("spmd2", NULL, 0, "", NPROC - 1, tids);
    if(n <  NPROC - 1){
      bail(tids, NPROC - 1, n);  
      pvm_exit();
      exit(EXIT_FAILURE);
    }
  }
  /* Wait for everyone to startup before proceeding. */
  pvm_freezegroup(GROUP, NPROC);
  pvm_barrier(GROUP, NPROC);
  /*------------------BARRIER----------------------------*/
  dowork(me, NPROC);
  /* program finished leave group and exit pvm      */
  pvm_lvgroup( GROUP );
  pvm_exit();
  exit(EXIT_SUCCESS);
}

/* Simple example passes a token around a ring         */

void dowork(int me, int nproc ){
  int token, src, dest, count  = 1, stride = 1, msgtag = 4;
  /* Determine neighbors in the ring                   */
  src  = pvm_gettid(GROUP, (me == 0 ? NPROC - 1 : me - 1));
  dest = pvm_gettid(GROUP, (me == NPROC - 1 ? 0 : me + 1));
  if(me == 0){ 
    token = TOKEN;
    pvm_initsend(PvmDataDefault);
    pvm_pkint(&token, count, stride);
    pvm_send(dest, msgtag);
    pvm_recv(src, msgtag);
    printf("token ring done\n");
  } else {
    pvm_recv(src, msgtag);
    pvm_upkint(&token, count, stride);
  
    /* Critical Section */
    printf( "I'm ring node %d\n", me );
    printf( "I'm ring node %d with token %d\n", me, token );

    pvm_initsend( PvmDataDefault );
    pvm_pkint(&token, count, stride);
    pvm_send(dest, msgtag);
  }
}

/* Shutdown if spawn fails                 */

void bail(int *tids, int tidmax, int actual){
  int i;
  fprintf(stderr,  "Trouble spawning. Aborting. Error codes are:\n");
  for(i = actual; i < tidmax; i++){
    printf("TID %d %d\n", i, tids[i]);
  }
  for(i = 0; i < actual; i++){
    pvm_kill(tids[i]);
  }
}