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bankalg.java
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bankalg.java
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import java.util.*;
class BankersAlgorithm
{
public static void main(String[] args)
{
/*
* Variables:
*
* n
* -number of processes
* -args[1]
*
* m
* -number of resource types
* -args[2]
*
* max
* -n x m matrix that stores the max demand of each process
* -If max[i][j] = k, then Process Pi may request at most k instances of resource Rj
*
* Allocation
* -n x m matrix that stores the # of each resource type currently allocated to each process
* -If allocation[i][j] = k, then process Pi is currently allocated k instances of resource Rj
*
* Need
* -n x m matrix that stores the remaining resource need of each process
* -if need[i][j] = k, then process Pi may need k more instances of resource type Rj to complete task.
* -need[i][j] = max[i][j] - allocation[i][j]
*
* ***************************************************************************************************
*
* Algorithm:
-Main algorithm is Resource Request algorithm, which depends on safety algorithm.
* -Safety algorithm determines if the current state is a safe state
* -Resource Request algorithm determines where a request can be safely granted.
*/
if(args.length != 1)
{
System.out.println("Missing request flag command line argument. Enter 0 or 1 and try again.");
System.exit(-1);
}
int option = Integer.parseInt(args[0]);
//available array
int[] available = {1, 5, 2, 0};
//max matrix
int[][] max = {
{0, 0, 1, 2},
{1, 7, 5, 0},
{2, 3, 5, 6},
{0, 6, 5, 2},
{0, 6, 5, 6}
};
//allocation matrix
int[][] allocation = {
{0, 0, 1, 2},
{1, 0, 0, 0},
{1, 3, 5, 4},
{0, 6, 3, 2},
{0, 0, 1, 4}
};
//need matrix
int[][] need = new int[5][4];
for (int x = 0; x < 5; x++)
for (int y = 0; y < 4; y++)
{
need[x][y] = max[x][y] - allocation[x][y];
//System.out.println("Need[" + x + "][" + y + "] - " + need[x][y]);
}
int request[] = new int[4];
if (option == 0)
{
request[0] = 0;
request[1] = 4;
request[2] = 2;
request[3] = 0;
}
else
{
request[0] = 1;
request[1] = 4;
request[2] = 2;
request[3] = 0;
for (int i = 0; i < 5; i++)
for (int j = 0; j < 4; j++)
{
need[i][j] += 15;
}
//need[1][0] = 20;
//need[1][1] = 20;
//need[1][2] = 20;
//need[1][3] = 20;
}
//step 1
System.out.println("Step 1 - Checking if request <= need");
boolean requestFlag = true;
boolean reqAvailFlag = true;
for (int x = 0; x < request.length; x++)
{
if (request[x] > need[1][x])
requestFlag = false;
if (request[x] > available[x])
reqAvailFlag = false;
}
if (requestFlag)
{
System.out.println("request[i] <= need[i]!");
}
else
{
System.out.println("Error - process[i] has exceeded its claim!");
System.exit(-1);
}
if (reqAvailFlag)
System.out.println("request[i] <= available[i]!");
else
{
System.out.println("Error - Request > available, process has to wait.");
System.exit(0);
}
//save old available and allocation and need, and then check if state is safe with new ones.
int[] oldAvailable = available;
int[][] oldAllocation = allocation;
int[][] oldNeed = need;
for(int x = 0; x < available.length; x++)
{
//System.out.println("available[" + x + "] = " + available[x]);
available[x] -= request[x];
//System.out.println("New available[" + x + "] = " + available[x]);
allocation[1][x] += request[x];
need[1][x] -= request[x];
}
//Call safety algorithm here to check if state is safe.
int[] work = new int[4];
for(int i = 0; i < 4; i++)
work[i] = available[i];
boolean[] finished = new boolean[5];
int count = 0;
while (count < 5)
{
boolean found = false;
for (int i = 0; i < 5; i++)
{
if (!finished[i])
{
boolean enough = true;
for (int j = 0; j < 4; j++)
{
if(need[i][j] > work[j])
{
enough = false;
break;
}
}
if (enough)
{
for (int j = 0; j < 4; j ++)
{
work[j] += allocation[i][j];
}
finished[i] = true;
found = true;
count++;
}
}
}
if (!found)
break;
}
boolean result;
if (count == 5)
{
result = true;
//System.out.println("result is true");
}
else
{
result = false;
//System.out.println("result is false");
}
if(result)
{
System.out.print("Request for Process 1 is: (");
for(int x = 0; x < request.length; x++)
if (x == request.length - 1)
System.out.print(request[x]);
else
System.out.print(request[x] + " ");
System.out.print(")\n");
System.out.println("Request generates a safe state, request is granted!.");
System.out.println("Need Matrix:");
for(int i = 0; i < 5; i++)
{
System.out.print("[");
for(int j = 0; j < 4; j++)
{
if(j == 3)
System.out.print(need[i][j]);
else
System.out.print(need[i][j] + ", ");
}
System.out.print("]\n");
}
System.out.print("Available: (");
for(int x = 0; x < available.length; x++)
if(x == available.length - 1)
System.out.print(available[x]);
else
System.out.print(available[x] + ", ");
System.out.println(")");
//print out need matrix and available array.
}
else
{
System.out.print("Request for Process 1 is: (");
for(int x = 0; x < request.length; x++)
if(x == request.length - 1)
System.out.print(request[x]);
else
System.out.print(request[x] + " ");
System.out.print(")\n");
System.out.println("Request doesn't generate a safe state, request cannot be granted!");
System.out.println("Need Matrix:");
for(int i = 0; i < 5; i++)
{
System.out.print("[");
for(int j = 0; j < 4; j++)
{
if(j == 3)
System.out.print(need[i][j]);
else
System.out.print(need[i][j] + ", ");
}
System.out.print("]\n");
}
System.out.print("Available: (");
for(int x = 0; x < available.length; x++)
if(x == available.length - 1)
System.out.print(available[x]);
else
System.out.print(available[x] + ", ");
System.out.println(")");
}
}
}