97 lines
3.6 KiB
Java
97 lines
3.6 KiB
Java
package Others;
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import java.util.ArrayList;
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/** @author Dekas Dimitrios */
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public class BestFit {
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private static final int NO_ALLOCATION =
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-255; // if a process has been allocated in position -255,
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// it means that it has not been actually allocated.
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/**
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* Method to find the maximum valued element of an array filled with positive integers.
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*
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* @param array: an array filled with positive integers.
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* @return the maximum valued element of the array.
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*/
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private static int findMaxElement(int[] array) {
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int max = -1;
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for (int value : array) {
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if (value > max) {
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max = value;
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}
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}
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return max;
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}
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/**
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* Method to find the index of the memory block that is going to fit the given process based on
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* the best fit algorithm.
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*
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* @param blocks: the array with the available memory blocks.
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* @param process: the size of the process.
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* @return the index of the block that fits, or -255 if no such block exists.
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*/
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private static int findBestFit(int[] blockSizes, int processSize) {
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// Initialize minDiff with an unreachable value by a difference between a blockSize and the
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// processSize.
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int minDiff = findMaxElement(blockSizes);
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int index =
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NO_ALLOCATION; // If there is no block that can fit the process, return NO_ALLOCATION as the
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// result.
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for (int i = 0;
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i < blockSizes.length;
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i++) { // Find the most fitting memory block for the given process.
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if (blockSizes[i] - processSize < minDiff && blockSizes[i] - processSize >= 0) {
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minDiff = blockSizes[i] - processSize;
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index = i;
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}
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}
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return index;
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}
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/**
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* Method to allocate memory to blocks according to the best fit algorithm. It should return an
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* ArrayList of Integers, where the index is the process ID (zero-indexed) and the value is the
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* block number (also zero-indexed).
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*
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* @param sizeOfBlocks: an int array that contains the sizes of the memory blocks available.
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* @param sizeOfProcesses: an int array that contains the sizes of the processes we need memory
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* blocks for.
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* @return the ArrayList filled with Integers repressenting the memory allocation that took place.
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*/
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static ArrayList<Integer> bestFit(int[] sizeOfBlocks, int[] sizeOfProcesses) {
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// The array list responsible for saving the memory allocations done by the best-fit algorithm
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ArrayList<Integer> memAlloc = new ArrayList<>();
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// Do this for every process
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for (int processSize : sizeOfProcesses) {
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int chosenBlockIdx =
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findBestFit(
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sizeOfBlocks, processSize); // Find the index of the memory block going to be used
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memAlloc.add(chosenBlockIdx); // Store the chosen block index in the memAlloc array list
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if (chosenBlockIdx
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!= NO_ALLOCATION) { // Only if a block was chosen to store the process in it,
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sizeOfBlocks[chosenBlockIdx] -= processSize; // resize the block based on the process size
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}
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}
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return memAlloc;
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}
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/**
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* Method to print the memory allocated.
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*
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* @param memAllocation: an ArrayList of Integer representing the memory allocation done by the
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* bestFit method.
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*/
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public static void printMemoryAllocation(ArrayList<Integer> memAllocation) {
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System.out.println("Process No.\tBlock No.");
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System.out.println("===========\t=========");
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for (int i = 0; i < memAllocation.size(); i++) {
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System.out.print(" " + i + "\t\t");
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if (memAllocation.get(i) != NO_ALLOCATION) System.out.print(memAllocation.get(i));
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else System.out.print("Not Allocated");
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System.out.println();
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}
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}
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}
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