Program for Next Fit algorithm in Memory Management
Last Updated : 05 May, 2023
Prerequisite: Partition allocation methods
What is Next Fit?
The next fit is a modified version of 'first fit'. It begins as the first fit to find a free partition but when called next time it starts searching from where it left off, not from the beginning. This policy makes use of a roving pointer. The pointer moves along the memory chain to search for the next fit. This helps in, to avoid the usage of memory always from the head (beginning) of the free blockchain.
What is its advantage over first fit?
- First fit is a straight and fast algorithm, but tends to cut a large portion of free parts into small pieces due to which, processes that need a large portion of memory block would not get anything even if the sum of all small pieces is greater than it required which is so-called external fragmentation problem.
- Another problem of the first fit is that it tends to allocate memory parts at the beginning of the memory, which may lead to more internal fragments at the beginning. Next fit tries to address this problem by starting the search for the free portion of parts not from the start of the memory, but from where it ends last time.
- Next fit is a very fast searching algorithm and is also comparatively faster than First Fit and Best Fit Memory Management Algorithms.
Example: Input : blockSize[] = {5, 10, 20}; processSize[] = {10, 20, 30}; Output: Process No. Process Size Block no. 1 10 2 2 20 3 3 30 Not Allocated Algorithm:
- Input the number of memory blocks and their sizes and initializes all the blocks as free.
- Input the number of processes and their sizes.
- Start by picking each process and check if it can be assigned to the current block, if yes, allocate the required memory and check for next process but from the block where we left not from starting.
- If the current block size is smaller then keep checking the further blocks.
Below is the implementation of the above approach:
C++ // C/C++ program for next fit // memory management algorithm #include <bits/stdc++.h> using namespace std; // Function to allocate memory to blocks as per Next fit // algorithm void NextFit(int blockSize[], int m, int processSize[], int n) { // Stores block id of the block allocated to a // process int allocation[n], j = 0, t = m - 1; // 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 < n; i++){ // Do not start from beginning while (j < m){ if(blockSize[j] >= processSize[i]){ // allocate block j to p[i] process allocation[i] = j; // Reduce available memory in this block. blockSize[j] -= processSize[i]; // sets a new end point t = (j - 1) % m; break; } if (t == j){ // sets a new end point t = (j - 1) % m; // breaks the loop after going through all memory block break; } // mod m will help in traversing the // blocks from starting block after // we reach the end. j = (j + 1) % m; } } cout << "\nProcess No.\tProcess Size\tBlock no.\n"; for (int i = 0; i < n; i++) { cout << " " << i + 1 << "\t\t\t\t" << processSize[i] << "\t\t\t\t"; if (allocation[i] != -1) cout << allocation[i] + 1; else cout << "Not Allocated"; cout << endl; } } // Driver program int main() { int blockSize[] = { 5, 10, 20 }; int processSize[] = { 10, 20, 5 }; int m = sizeof(blockSize) / sizeof(blockSize[0]); int n = sizeof(processSize) / sizeof(processSize[0]); NextFit(blockSize, m, processSize, n); return 0; } // Java program for next fit // memory management algorithm import java.util.*; public class GFG { // Function to allocate memory to blocks as per Next fit // algorithm static void NextFit(int blockSize[], int m, int processSize[], int n) { // Stores block id of the block allocated to a // process int allocation[] = new int[n], j = 0, t = m - 1; // Initially no block is assigned to any process Arrays.fill(allocation, -1); // pick each process and find suitable blocks // according to its size ad assign to it // pick each process and find suitable blocks // according to its size ad assign to it for(int i = 0; i < n; i++){ // Do not start from beginning while (j < m){ if(blockSize[j] >= processSize[i]){ // allocate block j to p[i] process allocation[i] = j; // Reduce available memory in this block. blockSize[j] -= processSize[i]; // sets a new end point t = (j - 1) % m; break; } if (t == j){ // sets a new end point t = (j - 1) % m; // breaks the loop after going through all memory block break; } // mod m will help in traversing the // blocks from starting block after // we reach the end. j = (j + 1) % m; } } System.out.print("\nProcess No.\tProcess Size\tBlock no.\n"); for (int i = 0; i < n; i++) { System.out.print( i + 1 + "\t\t\t\t" + processSize[i] + "\t\t\t\t"); if (allocation[i] != -1) { System.out.print(allocation[i] + 1); } else { System.out.print("Not Allocated"); } System.out.println(""); } } // Driver program public static void main(String[] args) { int blockSize[] = {5, 10, 20}; int processSize[] = {10, 20, 5}; int m = blockSize.length; int n = processSize.length; NextFit(blockSize, m, processSize, n); } } // This code is contributed by Rajput-Ji # Python3 program for next fit # memory management algorithm # Function to allocate memory to # blocks as per Next fit algorithm def NextFit(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 j = 0 t = m-1 # pick each process and find suitable blocks # according to its size ad assign to it for i in range(n): # Do not start from beginning while j < m: if blockSize[j] >= processSize[i]: # allocate block j to p[i] process allocation[i] = j # Reduce available memory in this block. blockSize[j] -= processSize[i] # sets a new end point t = (j - 1) % m break if t == j: # sets a new end point t = (j - 1) % m # breaks the loop after going through all memory block break # mod m will help in traversing the # blocks from starting block after # we reach the end. j = (j + 1) % m print("Process No. Process Size Block no.") for i in range(n): print("\t", i + 1, "\t\t\t", processSize[i],end = "\t\t\t") if allocation[i] != -1: print(allocation[i] + 1) else: print("Not Allocated") # Driver Code if __name__ == '__main__': blockSize = [5, 10, 20] processSize = [10, 20, 5] m = len(blockSize) n = len(processSize) NextFit(blockSize, m, processSize, n) // C# program for next fit // memory management algorithm using System; public class GFG { // Function to allocate memory to blocks as per Next fit // algorithm static void NextFit(int[] blockSize, int m, int[] processSize, int n) { // Stores block id of the block allocated to a // process int[] allocation = new int[n]; int j = 0, t = m - 1; // Initially no block is assigned to any process for (int i = 0; i < n; i++) allocation[i] = -1; // pick each process and find suitable blocks // according to its size ad assign to it // pick each process and find suitable blocks // according to its size ad assign to it for (int i = 0; i < n; i++) { // Do not start from beginning while (j < m) { if (blockSize[j] >= processSize[i]) { // allocate block j to p[i] process allocation[i] = j; // Reduce available memory in this // block. blockSize[j] -= processSize[i]; // sets a new end point t = (j - 1) % m; break; } if (t == j) { // sets a new end point t = (j - 1) % m; // breaks the loop after going through // all memory block break; } // mod m will help in traversing the // blocks from starting block after // we reach the end. j = (j + 1) % m; } } Console.Write( "\nProcess No.\tProcess Size\tBlock no.\n"); for (int i = 0; i < n; i++) { Console.Write(i + 1 + "\t\t\t\t" + processSize[i] + "\t\t\t\t"); if (allocation[i] != -1) { Console.Write(allocation[i] + 1); } else { Console.Write("Not Allocated"); } Console.WriteLine(""); } } // Driver program public static void Main(string[] args) { int[] blockSize = { 5, 10, 20 }; int[] processSize = { 10, 20, 5 }; int m = blockSize.Length; int n = processSize.Length; NextFit(blockSize, m, processSize, n); } } // This code is contributed by karandeep1234 <?php // PHP program for next fit // memory management algorithm // Function to allocate memory to blocks as per Next fit // algorithm function NextFit($blockSize, $m, $processSize, $n) { // Stores block id of the block allocated to a // process $allocation = array_fill(0, $n, -1); $j = 0; $t = $m - 1; // Initially no block is assigned to any process above // pick each process and find suitable blocks // according to its size ad assign to it for($i = 0; $i < $n; $i++){ // Do not start from beginning while ($j < $m){ if($blockSize[$j] >= $processSize[$i]){ // allocate block j to p[i] process $allocation[$i] = $j; // Reduce available memory in this block. $blockSize[$j] -= $processSize[$i]; // sets a new end point $t = ($j - 1) % $m; break; } if ($t == $j){ // sets a new end point $t = ($j - 1) % $m; // breaks the loop after going through all memory block break; } // mod m will help in traversing the // blocks from starting block after // we reach the end. $j = ($j + 1) % $m; } } echo "\nProcess No.\tProcess Size\tBlock no.\n"; for ($i = 0; $i < $n; $i++) { echo " ".($i + 1)."\t\t\t\t".$processSize[$i]."\t\t\t\t"; if ($allocation[$i] != -1) echo ($allocation[$i] + 1); else echo "Not Allocated"; echo "\n"; } } // Driver program $blockSize = array( 5, 10, 20 ); $processSize = array( 10, 20, 5 ); $m = count($blockSize); $n = count($processSize); NextFit($blockSize, $m, $processSize, $n); // This code is contributed by mits ?> // Function to allocate memory to blocks as per Next fit // memory management algorithm function NextFit(blockSize, m, processSize, n) { // Stores block id of the block allocated to a // process let allocation = new Array(n).fill(-1); let j = 0, t = m - 1; // pick each process and find suitable blocks // according to its size ad assign to it for (let i = 0; i < n; i++) { // Do not start from beginning while (j < m) { if (blockSize[j] >= processSize[i]) { // allocate block j to p[i] process allocation[i] = j; // Reduce available memory in this block. blockSize[j] -= processSize[i]; // sets a new end point t = (j - 1) % m; break; } if (t == j) { // sets a new end point t = (j - 1) % m; // breaks the loop after going through all memory block break; } // mod m will help in traversing the // blocks from starting block after // we reach the end. j = (j + 1) % m; } } console.log("\nProcess No.\tProcess Size\tBlock no.\n"); for (let i = 0; i < n; i++) { console.log(" " + (i + 1) + "\t\t\t\t" + processSize[i] + "\t\t\t\t"); if (allocation[i] != -1) console.log(allocation[i] + 1); else console.log("Not Allocated"); console.log("\n"); } } // Driver program let blockSize = [5, 10, 20]; let processSize = [10, 20, 5]; let m = blockSize.length; let n = processSize.length; NextFit(blockSize, m, processSize, n); OutputProcess No. Process Size Block no. 1 10 2 2 20 3 3 5 1
Time Complexity: O(N*M) where N is processSize length and M is blockSize length.
Auxiliary Space: O(N)
How does the Next Fit algorithm help in reducing memory fragmentation?
The Next Fit algorithm helps in reducing memory fragmentation by leaving larger gaps between allocated partitions, which can be used for future allocations. This reduces the number of small gaps and helps in allocating larger contiguous blocks of memory to processes.
Similar Reads
Program for Best Fit algorithm in Memory Management Prerequisite : Partition allocation methodsBest fit allocates the process to a partition which is the smallest sufficient partition among the free available partitions. Example: Input : blockSize[] = {100, 500, 200, 300, 600}; processSize[] = {212, 417, 112, 426}; Output: Process No. Process Size Bl
8 min read
Program for First Fit algorithm in Memory Management Prerequisite : Partition Allocation MethodsIn the first fit, the partition is allocated which is first sufficient from the top of Main Memory.Example : Input : blockSize[] = {100, 500, 200, 300, 600}; processSize[] = {212, 417, 112, 426};Output:Process No. Process Size Block no. 1 212 2 2 417 5 3 11
8 min read
Program for Worst Fit algorithm in Memory Management Prerequisite : Partition allocation methodsWorst 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 : blo
8 min read
Program for Best Fit algorithm in Memory Management using Linked List Best fit algorithm for memory management: The memory partition in which there is a minimum loss on the allocation of the process is the best-fit memory partition that is allocated to the process.We have already discussed one best-fit algorithm using arrays in this article. However, here we are going
15+ min read
First Fit algorithm in Memory Management using Linked List First Fit Algorithm for Memory Management: The first memory partition which is sufficient to accommodate the process is allocated.We have already discussed first fit algorithm using arrays in this article. However, here we are going to look into another approach using a linked list where the deletio
15+ min read