include #include #include #include

#include <stdio.h> #include <stdlib.h> #include <pthread.h> #include <unistd.h>

ID: 3594410 • Letter: #

Question

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>

#define MAX_BR_CAP 5
#define CROSS_TIME 4
#define DIREC_PROB 0.7

#define handle_err(s) do{perror(s); exit(EXIT_FAILURE);}while(0)

typedef struct _thread_argv
{
   int vid;
   int direc;
   int time_to_cross;
} thread_argv;

typedef struct _bridge {
   int dept_idx;
   int num_car;
   int curr_dir;
} bridge_t;

void bridge_init();
void bridge_destroy();
void dispatch(int n);
void *OneVehicle(void *argv);
void ArriveBridge(int vid, int direc);
void CrossBridge(int vid, int direc, int time_to_cross);
void ExitBridge(int vid, int direc);

pthread_t *threads = NULL;   /* Array to hold thread structs */
thread_argv *args = NULL;   /* Array to hold thread arguments */
int num_v = 30;           /* Total number of vehicles to be created */

bridge_t br; /* Bridge struct shared by the vehicle threads*/

int main(int argc, char *argv[])
{
int sched_opt;
int i;

   if(argc < 2)
   {
       printf("Usage: %s SCHED_OPT [SEED] ", argv[0]);
       exit(EXIT_SUCCESS);
   }

   /* Process Arguments */
   sched_opt = atoi(argv[1]);
   if(argc == 3)
       srand((unsigned int)atoi(argv[2]));
   else
       srand((unsigned int)time(NULL));

   /* Allocate memory for thread structs and arguments */
   if((threads = (pthread_t *)malloc(sizeof(pthread_t) * num_v)) == NULL)
       handle_err("malloc() Failed for threads");
   if((args = (thread_argv *)malloc(sizeof(thread_argv) * num_v)) == NULL)
       handle_err("malloc() Failed for args");

/* Init bridge struct */
bridge_init();

   /* Create vehicle threads */
   switch(sched_opt)
   {
       case 1 : dispatch(5); break;
       case 2 : dispatch(10); break;
       case 3 : dispatch(30); break;
       default:
           fprintf(stderr, "Bad Schedule Option %d ", sched_opt);
           exit(EXIT_FAILURE);
   }

   /* Join all the threads */
   for(i = 0; i < num_v; i++)
       pthread_join(threads[i], NULL);

/* Clean up and exit */
bridge_destroy();

exit(EXIT_SUCCESS);
}

/**
*   Create n vehicle threads for every 10 seconds until the total
*    number of vehicles reaches num_v
*   Each thread handle is stored in the shared array - threads
*/
void dispatch(int n)
{
int k, i;

   for(k = 0; k < num_v; k += n)
   {
       printf("Dispatching %d vehicles ", n);

       for( i = k; i < k + n && i < num_v; i++)
       {
           /* The probability of direction 0 is DIREC_PROB */
           int direc = rand() % 1000 > DIREC_PROB * 1000 ? 0 : 1;

           args[i] = (thread_argv){i, direc, CROSS_TIME};
           if(pthread_create(threads + i, NULL, &OneVehicle, args + i) != 0)
               handle_err("pthread_create Failed");
       }

       printf("Sleep 10 seconds "); sleep(10);
   }
}

void *OneVehicle(void *argv)
{
thread_argv *args = (thread_argv *)argv;

   ArriveBridge(args->vid, args->direc);
   CrossBridge(args->vid, args->direc, args->time_to_cross);
   ExitBridge(args->vid, args->direc);

pthread_exit(0);
}

void bridge_init()
{
   br.dept_idx = 0;
   br.curr_dir = 0;
   br.num_car = 0;

return;
}

void bridge_destroy()
{
   br.dept_idx=NULL;
   br.curr_dir=NULL;
   br.num_car=NULL;
   return;
}

void ArriveBridge(int vid, int direc)
{

return;
}

void CrossBridge(int vid, int direc, int time_to_cross)
{
   fprintf(stderr, "vid=%d dir=%d starts crossing. Bridge num_car=%d curr_dir=%d ",
       vid, direc, br.num_car, br.curr_dir);
   sleep(time_to_cross);
   return;
}

void ExitBridge(int vid, int direc)
{
   fprintf(stderr, "vid=%d dir=%d exit with departure idx=%d ",
       vid, direc, br.dept_idx);
   return;
}

The goal of this exercise to give you some experience writing concurrent programs using the Pthreads multi-threaded programming library. You have been hired by MetroTrans to synchronize traffic over a one-lane bridge on a public highway. Traffic may only cross the bridge in one direction at a time. Moreoverthe bridge is really old and hasn't been repaired for lack of funds, so MetroTrans has decided to impose the restriction that there should never be more than 5 vehicles on the bridge at any given time. (If this limit is exceeded the bridge will collapse). In this system, each vehicle is represented by one thread, which executes the procedure Onevehicle when it arrives at the bridge: OneVehicle (int direc, int time_to_cross) { ArriveBridge (vehicle_id, direc); CrossBridge (vehicle_id, direc, time_to_cross) ; ExitBridge (vehicle_id, direc) ; In the code above, vehicle_id is an integer which uniquely identifies each vehicle. (The vehicles arriv- ing at the bridge should be assigned vehicle_ids 1,2,3... and so on. ) direc is either 0 correspond ing to east or 1 corresponding to west; it gives the direction in which the vehicle will cross the bridge. time_to_cross is the time it takes a vehicle to cross the bridge - assume that every vehicle takes 4 seconds to cross the bridge.

Explanation / Answer

bridge_t br = new bridge_t;

bridge_destroy(){

    br.dept_idx=NULL;
   br.curr_dir=NULL;
   br.num_car=NULL;

delete br;
return ;

}

int numV = 5; // add this in the beginning of the code

void ArriveBridge(int vid, int direc)
{

if (numV > 0)

{

fprintf(“Vehicle has arrived on the bridge”);

numV--;

}

else

while(numV <= 0);

return;
}

int departure_index =1;

void ExitBridge(int vid, int direc)
{
   fprintf(stderr, "vid=%d dir=%d exit with departure idx=%d ",
       vid, direc, br.dept_idx);
      departure_index++;              // increment departure_index

numV++; // increment numV so that another vehicle can come to bridge

return;

}

I have explained this code in detail in your previous question. This answer is in continuation with that so not adding minute details of other portion of the code here. If this helps please give a thumbs up. Good Luck!!

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#include <stdio.h> #include <stdlib.h> #include <process.h> #include <time.h> #d

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#include <stdio.h> #include <stdlib.h> #include <pthread.h> #include <unistd.h>

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