Program for Worst Fit algorithm in Memory Management

• Difficulty Level : Easy
• Last Updated : 28 Jun, 2021

Prerequisite : Partition allocation methods
Worst Fit allocates a process to the partition which is largest sufficient among the freely available partitions available in the main memory. If a large process comes at a later stage, then memory will not have space to accommodate it.

Example:

Input : blockSize[]   = {100, 500, 200, 300, 600};
processSize[] = {212, 417, 112, 426};
Output:
Process No.    Process Size    Block no.
1        212        5
2        417        2
3        112        5
4        426        Not Allocated Implementation:
1- Input memory blocks and processes with sizes.
2- Initialize all memory blocks as free.
3- Start by picking each process and find the
maximum block size that can be assigned to
current process i.e., find max(bockSize,
blockSize,.....blockSize[n]) >
processSize[current], if found then assign
it to the current process.
5- If not then leave that process and keep checking
the further processes.

Below is implementation of above steps.

C++

 // C++ implementation of worst - Fit algorithm#includeusing namespace std; // Function to allocate memory to blocks as per worst fit// algorithmvoid worstFit(int blockSize[], int m, int processSize[],                                                 int n){    // Stores block id of the block allocated to a    // process    int allocation[n];     // Initially no block is assigned to any process    memset(allocation, -1, sizeof(allocation));     // pick each process and find suitable blocks    // according to its size ad assign to it    for (int i=0; i= processSize[i])            {                if (wstIdx == -1)                    wstIdx = j;                else if (blockSize[wstIdx] < blockSize[j])                    wstIdx = j;            }        }         // If we could find a block for current process        if (wstIdx != -1)        {            // allocate block j to p[i] process            allocation[i] = wstIdx;             // Reduce available memory in this block.            blockSize[wstIdx] -= processSize[i];        }    }     cout << "\nProcess No.\tProcess Size\tBlock no.\n";    for (int i = 0; i < n; i++)    {        cout << "   " << i+1 << "\t\t" << processSize[i] << "\t\t";        if (allocation[i] != -1)            cout << allocation[i] + 1;        else            cout << "Not Allocated";        cout << endl;    }} // Driver codeint main(){    int blockSize[] = {100, 500, 200, 300, 600};    int processSize[] = {212, 417, 112, 426};    int m = sizeof(blockSize)/sizeof(blockSize);    int n = sizeof(processSize)/sizeof(processSize);     worstFit(blockSize, m, processSize, n);     return 0 ;}

Java

 // Java implementation of worst - Fit algorithm public class GFG{    // Method to allocate memory to blocks as per worst fit    // algorithm    static void worstFit(int blockSize[], int m, int processSize[],                                                     int n)    {        // Stores block id of the block allocated to a        // process        int allocation[] = new int[n];              // Initially no block is assigned to any process        for (int i = 0; i < allocation.length; i++)            allocation[i] = -1;              // pick each process and find suitable blocks        // according to its size ad assign to it        for (int i=0; i= processSize[i])                {                    if (wstIdx == -1)                        wstIdx = j;                    else if (blockSize[wstIdx] < blockSize[j])                        wstIdx = j;                }            }                  // If we could find a block for current process            if (wstIdx != -1)            {                // allocate block j to p[i] process                allocation[i] = wstIdx;                      // Reduce available memory in this block.                blockSize[wstIdx] -= processSize[i];            }        }              System.out.println("\nProcess No.\tProcess Size\tBlock no.");        for (int i = 0; i < n; i++)        {            System.out.print("   " + (i+1) + "\t\t" + processSize[i] + "\t\t");            if (allocation[i] != -1)                System.out.print(allocation[i] + 1);            else                System.out.print("Not Allocated");            System.out.println();        }    }         // Driver Method    public static void main(String[] args)    {         int blockSize[] = {100, 500, 200, 300, 600};         int processSize[] = {212, 417, 112, 426};         int m = blockSize.length;         int n = processSize.length;                   worstFit(blockSize, m, processSize, n);    }}

Python3

 # Python3 implementation of worst - Fit algorithm # Function to allocate memory to blocks as# per worst fit algorithmdef worstFit(blockSize, m, processSize, n):         # Stores block id of the block    # allocated to a process         # Initially no block is assigned    # to any process    allocation = [-1] * n         # pick each process and find suitable blocks    # according to its size ad assign to it    for i in range(n):                 # Find the best fit block for        # current process        wstIdx = -1        for j in range(m):            if blockSize[j] >= processSize[i]:                if wstIdx == -1:                    wstIdx = j                elif blockSize[wstIdx] < blockSize[j]:                    wstIdx = j         # If we could find a block for        # current process        if wstIdx != -1:                         # allocate block j to p[i] process            allocation[i] = wstIdx             # Reduce available memory in this block.            blockSize[wstIdx] -= processSize[i]     print("Process No. Process Size Block no.")    for i in range(n):        print(i + 1, "         ",              processSize[i], end = "     ")        if allocation[i] != -1:            print(allocation[i] + 1)        else:            print("Not Allocated") # Driver codeif __name__ == '__main__':    blockSize = [100, 500, 200, 300, 600]    processSize = [212, 417, 112, 426]    m = len(blockSize)    n = len(processSize)     worstFit(blockSize, m, processSize, n) # This code is contributed by PranchalK

C#

 // C# implementation of worst - Fit algorithmusing System; class GFG{    // Method to allocate memory to blocks     // as per worst fit algorithm    static void worstFit(int []blockSize, int m,                        int []processSize, int n)    {        // Stores block id of the block allocated to a        // process        int []allocation = new int[n];             // Initially no block is assigned to any process        for (int i = 0; i < allocation.Length; i++)            allocation[i] = -1;             // pick each process and find suitable blocks        // according to its size ad assign to it        for (int i = 0; i < n; i++)        {            // Find the best fit block for current process            int wstIdx = -1;            for (int j = 0; j < m; j++)            {                if (blockSize[j] >= processSize[i])                {                    if (wstIdx == -1)                        wstIdx = j;                    else if (blockSize[wstIdx] < blockSize[j])                        wstIdx = j;                }            }                 // If we could find a block for current process            if (wstIdx != -1)            {                // allocate block j to p[i] process                allocation[i] = wstIdx;                     // Reduce available memory in this block.                blockSize[wstIdx] -= processSize[i];            }        }             Console.WriteLine("\nProcess No.\tProcess Size\tBlock no.");        for (int i = 0; i < n; i++)        {            Console.Write(" " + (i+1) + "\t\t\t" + processSize[i] + "\t\t\t");            if (allocation[i] != -1)                Console.Write(allocation[i] + 1);            else                Console.Write("Not Allocated");            Console.WriteLine();        }    }         // Driver code    public static void Main(String[] args)    {        int []blockSize = {100, 500, 200, 300, 600};        int []processSize = {212, 417, 112, 426};        int m = blockSize.Length;        int n = processSize.Length;                 worstFit(blockSize, m, processSize, n);    }} // This code has been contributed by 29AjayKumar

Javascript



Output:

Process No.    Process Size    Block no.
1        212        5
2        417        2
3        112        5
4        426        Not Allocated

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