/*

  A simple test file to illustrate both spawning off processes and
  passing messages

*/

#include <iostream.h>
#include "pvm3.h"

int main()
{
	int success, tid;
	char message[100];

	//The function pvm_mytid() returns the tid of this process.
	// Each process has a unique tid that can be used to 
	// send messages to specific processes
	
	cout<<"i'm t"<<pvm_mytid()<<endl;

	//We are going to spawn off another process, with the
	// executable name "hello_other"

	success = pvm_spawn("hello_other", (char**)0, 0, "", 1, &tid);

	//the arguments to pvm_spawn are as follows:
	// 1) A character string that is the name of the executable
	// 2) A char** that is the array of arguments passed to the executable 
	//    as command line parameters
	// 3) An integer that is a flag that determines where to spawn
	//    off processes.  For now leave it as 0.
	// 4) A character pointer used with the flag.  Leave as "" for now.
	// 5) An integer representing the number of processes you want to 
	//    spawn off.
	// 6) An integer pointer where the tids of the children are located
	//
	// pvm_spawn returns the number of processes actually started by 
	// this call to pvm_spawm

	if (success == 1) 
	{

	  //It was successfully spawned off so I will wait for it
	  // to send me a message
	  
	  int bufid = pvm_recv(-1, -1);

	  // pvm_recv has the following arguments:
	  // 1) An integer specifying what tid to accept a message from.
	  //    A value of -1 specifies that it will accept a message from
	  //    any process.
	  // 2) An integer representing a message id.  Like the previous
	  //    argument, a value of -1 will accept any message.
	  //
	  // pvm_recv returns an integer representing the buffer it put
	  // the message into

	  //Once we are here we have received the message and need to
	  // find out what was sent to us.

	  int num_bytes, message_id;

	  pvm_bufinfo(bufid, &num_bytes, &message_id, &tid);

	  //pvm_bufinfo has the following arguments:
	  // 1) An integer representing the buffer where the message is.
	  // 2) An integer pointer where the number of bytes sent will be
	  //    stored.
	  // 3) An integer pointer where the message tag will be stored
	  // 4) An integer pointer where the tid who sent it will be stored.

	  pvm_upkstr(message);

	  //Unpacks the string and places it in a message buffer
	  // Unpacking is done in the same order as packing

	  printf("from t%x: %s\n", tid, message);

	} 
	else
	{
		printf("can't start hello_other\n");
	}

	//When a process is going to end, it must call pvm_exit() 
	// to inform pvm it is finished

	pvm_exit();

	return 0;
}