bankers_algo.cpp

#include <bits/stdc++.h>

using namespace std;

class Bankers_Table { // All the contents of the table

    public:
        int r_no, p_no; // Number of resources, Number of processes
        
        int *instances; // To store the number of instances for each resource
        int *available; // To store the available resources

        int **allocated; // To store the allocated resource for each process
        int **max_need; // To store the maximum required resource for each process
        int **need; // To store the required number of resources for each process.

        int available_resources(){ // Function to calculate available resource instances
            int sum, i, j, flag = 0;
            for(i=0; i<r_no; i++){
                sum = 0;
                for(j=0; j<p_no; j++){
                    sum += allocated[j][i];
                }
                available[i] = instances[i] - sum;
                if( available[i] < 0 ) flag = 1;
            }
            if( flag == 1) return -1;
            return 1;
        }

        void remaining_required(){
            int i, j;
            for(i=0; i<p_no; i++)
                for(j=0; j<r_no; j++)
                    need[i][j] = max_need[i][j] - allocated[i][j];
        }

        // Prints the table
        void print_table(){
            int i, j;

            cout << "\nInstances: ";
            for(i=0; i<r_no; i++) cout << instances[i] << " ";
            
            cout << "\nInitially Available: ";
            for(i=0; i<r_no; i++) cout << available[i] << " ";

            cout << "\nID | Allocated | Total Need | Remaining Need\n";
            for( i=0; i<p_no; i++){
                cout << "P" << i+1 << " | ";
                for( j=0; j<r_no; j++ ) cout << allocated[i][j] << " "; // Allocated instances
                cout << " | ";
                for( j=0; j<r_no; j++ ) cout << max_need[i][j] << " "; // Maximum required
                cout << " | ";
                for( j=0; j<r_no; j++ ) cout << need[i][j] << " "; // Remaining instances required
                cout << "\n";
            }
            cout << "\n";
        }

};

int *array_memory_allocation(int size) { // Memory Allocation Function for 1-D array
    int *p = new int [size];
    return p;
}

int **matrix_memory_allocation(int col, int row) { // Memory Allocation Function for 2-D array
    int **p;
    p = new int* [col];
    for(int i=0; i<col; i++ ) p[i] = new int [row];
    return p;
}

void bankers_algorithm(Bankers_Table a, int* v, int* f) {

    int i, j, k, count, flag;

    int temp_avail[a.r_no];
    for( i=0; i<a.r_no; i++) 
        temp_avail[i] = a.available[i];

    count = 0;
    while( count < (a.p_no-1) ) {
        flag = 0;
        for( i=0; i<a.p_no; i++ ) {
            if( f[i] == 0 )
            {
                for( j=0; j<a.r_no; j++ ) 
                    if( a.need[i][j] > temp_avail[i] ) 
                        break;
                
                if( j == a.r_no ) {
                    for( k=0; k<a.r_no; k++ )
                        temp_avail[k] += a.max_need[i][k];

                    v[count++] = i;
                    f[i] = 1;
                    flag = 1;
                }
            }
        }
    }
    if( flag == 0) {
        cout << "\nNo sequence found, Execution UNSAFE\n";
        return ;
    }

    cout << "\nSafe sequence found, Execution SAFE\nSequence: ";
    for( i=0; i<a.p_no; i++ )
        cout << "P" << v[i] +1 << " ";
    cout << "\n\n";
}

int BankersAlgo() {

    int *v; // Stores the sequence of processes that will be executed
    int *f; // Array to check if the process is executed

    int i, j;
    Bankers_Table t;

    cout << "Banker's Algorithm\n\nEnter the number of Resources: ";
    cin >> t.r_no;

    t.instances = array_memory_allocation(t.r_no);
    t.available = array_memory_allocation(t.r_no);
    v = array_memory_allocation(t.p_no); // Stores the sequence of processes
    f = array_memory_allocation(t.p_no); // Checks if the process is executed

    cout << "Enter the max number of each Resource\n";
    for( i=0; i < t.r_no; i++ ) {
        printf("%c: ", i+65);
        cin >> t.instances[i];
    }

    cout << "\nEnter the number of Processes: ";
    cin >> t.p_no;

    t.allocated = matrix_memory_allocation(t.p_no, t.r_no);
    t.max_need = matrix_memory_allocation(t.p_no, t.r_no);
    t.need = matrix_memory_allocation(t.p_no, t.r_no);

    cout << "Enter the allocated resources for each process (A B C ...)\n";
    for( i=0; i<t.p_no; i++ ) {
        
        cout << "Process P" << i+1 << ": ";
        for( j=0; j < t.r_no; j++ )
            cin >> t.allocated[i][j];
    }

    cout << "\nEnter the Maximum required resources for each process (A B C ...)\n";
    for( i=0; i < t.p_no; i++ ) {

        cout << "Process P" << i+1 << ": ";
        for( j=0; j < t.r_no; j++ )
            cin >> t.max_need[i][j];
    }

    int check=0;

    check = t.available_resources(); // Calculates the available resources
    if( check == -1 ) {
        cout << "\nInvalid Number of Available Resources\nExiting Program......\n\n";
        return 0;
    }
    t.remaining_required(); // Updates the value of remaining resources required for each process
    t.print_table(); // Prints the table
    bankers_algorithm(t, v, f);

    return 0;
}