switch_simulation.c

#include <iostream>
#include <chrono>
#include <random>

#define DOUBLE_PRECISION 10000
#define LAMBDA 5

using namespace std;

struct packet {
    int data;
    unsigned int src_port;
    unsigned int dst_port;
    struct packet *next;
};

struct packet* front = NULL;
struct packet* rear = NULL;
struct packet* temp;

void Insert(struct packet * rear, int val, unsigned int src_port, unsigned int dst_port) {

    cout<<"going to Insert " << val << " in queue : "<<endl;
    if (rear == NULL) {
        rear = (struct packet *)malloc(sizeof(struct packet));
        rear->next = NULL;
        rear->data = val;
        rear->src_port = src_port;
        rear->dst_port = dst_port;
        front = rear;
    } else {
        temp=(struct packet *)malloc(sizeof(struct packet));
        rear->next = temp;
        temp->data = val;
        temp->src_port = src_port;
        temp->dst_port = dst_port;
        temp->next = NULL;
        rear = temp;
    }
}

void Delete() {
    temp = front;
    if (front == NULL) {
        cout<<"Underflow"<<endl;
        return;
    }
    else
        if (temp->next != NULL) {
            temp = temp->next;
            cout<<"Element deleted from queue is : "<< front->data <<endl;
            free(front);
            front = temp;
        } else {
            cout<<"Element deleted from queue is : "<<front->data<<endl;
            free(front);
            front = NULL;
            rear = NULL;
        }
}

void Display() {
    temp = front;
    if ((front == NULL) && (rear == NULL)) {
        cout<<"Queue is empty"<<endl;
        return;
    }
    cout<<"Queue elements are: ";
    while (temp != NULL) {
        cout<< temp->data <<", "<< temp->src_port <<", "<< temp->dst_port <<" ";
        temp = temp->next;
    }
    cout<<endl;
}

unsigned int factorial(unsigned int n)
{
    if(n == 0) return 1;

    int res = 1, i;
    for (i = 2; i <= n; i++)
        res *= i;
    return res;
}


int poisson_rand(int lambda)
{
    double temp;
    unsigned seed = chrono::system_clock::now().time_since_epoch().count();
    srand(seed);
    temp = rand() % DOUBLE_PRECISION;
    double uni_rand = temp/DOUBLE_PRECISION;
    cout << "Using uniform rand as: " << uni_rand << endl;

    double sum = 0;
    for(int k=0; sum <= uni_rand; k++)
    {
        sum += exp(-lambda)*pow(lambda,k)/factorial(k);
        if (sum > uni_rand)
        {
            if(k>0)
                return (k-1);
            else
                return(k);
        }
    }
}

int main()
{

    int iter_count = 100;
    int buff_sz = 10, arr_rate = 5, dep_rate = 50;

    for(int i=1; i<iter_count ; i++)
    {
        int p_rand = poisson_rand(10);
        cout  << "[" << i << "] " << "Poisson distributed no (lambda = " << LAMBDA << "): " << p_rand << endl;
        cout << endl;
        Insert(rear, p_rand, rand()%1000, rand()%1000);
    }

    Display();

    return 0;

}