22 Program for Resource Allocation Algorithm in OS ~ Coding Atharva

Program:
   
// Banker's Algorithm
// Resource Allocation Algorithm
/*
5
3
1 1 2
2 1 2
4 0 1
0 2 0
1 1 2

4 3 3
3 2 2
9 0 2
7 5 3
1 1 2

2 1 0
*/
#include <iostream>
#include <unistd.h>
using namespace std;

int n, m;

// Function to display Matrix
void display(int mat[5][3])
{
    for (int i = 0; i < n; i++)
    {
        cout << endl;
        for (int j = 0; j < m; j++)
        {
            cout << mat[i][j] << " ";
        }
    }
}

// Function to check safety
bool safety(int available[5], int need[5][3], int alloc[5][3])
{
    // Step 2: Creating Flag variable to keep track of which process complete
    int flag[n];

    for (int i = 0; i < n; i++)
    {
        flag[i] = 0;
    }

    // Step 3: Allocating Resources if available is greater than need
    int safe_seq[n], ct = 0;
    int i, j, k, f;

    for (k = 0; k < n; k++)
    {
        for (i = 0; i < n; i++)
        {
            f = 0;
            if (flag[i] == 1)
            {
                continue;
            }

            for (j = 0; j < m; j++)
            {
                if (available[j] < need[i][j])
                {
                    f = 0;
                    break;
                }
                else
                {
                    f = 1;
                }
            }
            if (f == 1)
            {
                flag[i] = 1;
                break;
            }
        }

        if (i == n)
        {
            continue;
        }

        if (flag[i] == 1)
        {
            safe_seq[ct] = i;
            ct++;
            for (j = 0; j < m; j++)
            {
                available[j] += alloc[i][j];
            }
        }
    }

    for (int i = 0; i < n; i++)
    {
        if (flag[i] == 0)
        {
            return false;
        }
    }

    return true;
}

bool check(int resources[3], int need[5][3], int available[3], int p_no)
{
    // Check if request is less than need
    for (int j = 0; j < m; j++)
    {
        if (resources[j] > need[p_no][j])
        {
            cout << "\n\n Request is greater than Need";
            return false;
        }
    }

    // Check if request is less than available
    for (int j = 0; j < m; j++)
    {
        if (resources[j] > available[j])
        {
            cout << "\n\n Request is greater than Available";
            return false;
        }
    }
    return true;
}

int main()
{
    // freopen("input.txt", "r", stdin);

    cout << "\n\n Enter number of process:";
    cin >> n;

    cout << "\n\n Enter number of resources:";
    cin >> m;

    int alloc[n][3], need[n][3], max[n][3];
    int available[m];

    cout << "\n\n Enter Allocation Matrix:";
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < m; j++)
        {
            cin >> alloc[i][j];
        }
    }

    cout << "\n\n Enter Max Matrix:";
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < m; j++)
        {
            cin >> max[i][j];
        }
    }

    cout << "\n\n Enter available Array:";
    for (int i = 0; i < m; i++)
    {
        cin >> available[i];
    }

    cout << "\n\n Displaying Allocation Matrix:";
    display(alloc);

    cout << "\n\n Displaying Max Matrix:";
    display(max);

    cout << "\n\n Displaying Available Array:";
    for (int i = 0; i < m; i++)
    {
        cout << available[i] << " ";
    }

    // Step 1: Creating Need matix
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < m; j++)
        {
            need[i][j] = max[i][j] - alloc[i][j];
        }
    }

    cout << "\n\n Displaying Need Matrix:";
    display(need);

    // Taking Input for Resource Request
    int p_no, resources[m];

    cout << "\n\n Enter Process Number you want to allocate resource:";
    cin >> p_no;

    cout << "\n\n Enter Resouces " << m << ":";
    for (int i = 0; i < m; i++)
    {
        cin >> resources[i];
    }

    cout << "\n Requested for Process:" << p_no;
    cout << "\n\n Requested Resources:";
    for (int i = 0; i < m; i++)
    {
        cout << resources[i] << " ";
    }

    p_no = p_no - 1;

    if (!check(resources, need, available, p_no))
    {
        return 0;
    }

    // Now Request is less than available and need
    // allocate the resources
    for (int i = 0; i < m; i++)
    {
        alloc[p_no][i] += resources[i];
        available[i] -= resources[i];
        need[p_no][i] -= resources[i];
    }

    if (safety(available, need, alloc))
    {
        cout << "\n\n Requested Resources Can be Allocated!";
    }
    else
    {
        cout << "\n\n Requested Resources Cannot be Allocated!";
    }

    return 0;
}
Output:
1) Request Can Be Granted:
2) When Resources Cannot be Allocated:
22 Program for Resource Allocation Algorithm in OS

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