opt.java

页面置换算法 包括fifo 先进现出

package 操作系统.各个置换算法;

import javax.swing.JOptionPane;

public class Opt {
	public static final int PROGRAMLEN = 12;
	public static final int PROGRAMNUM = 5;
	public static final int PAGELEN = 3;

	public static void main(String[] args) {

		int[] program = new int[PROGRAMLEN]; // program为要装入的程序
		for (int i = 0; i < PROGRAMLEN; i++) {
			program[i] = (int) (Math.random() * PROGRAMNUM + 1);
		}
		// int[] program = { 5, 5, 5, 5, 1, 5, 2, 3, 1, 3, 3, 4 };//------5
		// int[] program = { 2, 3, 2, 1, 5, 2, 4, 5, 3, 2, 5, 2 };//------6 opt
		// int[] program = { 4, 3, 5, 5, 1, 5, 3, 4, 1, 1, 4, 2 };//------6
		// int[] program = { 3, 1, 3, 2, 5, 2, 3, 4, 1, 4, 3, 5 };// ------7
		for (int pro : program)
			System.out.print(" " + pro);
		System.out.println("");

		int[] page = new int[PAGELEN];
		for (int i = 0; i < PAGELEN; i++)
			page[i] = 0;

		int[] index = new int[PAGELEN];
		for (int i = 0; i < PAGELEN; i++)
			index[i] = 0;

		int lostPage = 0;
		for (int i = 0; i < PROGRAMLEN; i++) {

			int j = 0;
			for (j = 0; j < PAGELEN; j++)
				if (program[i] == page[j])
					break;
			if (j < PAGELEN)
				continue;

			lostPage++;
			for (j = 0; j < PAGELEN; j++)
				if (page[j] == 0) {
					page[j] = program[i];
					break;
				}
			if (j < PAGELEN)
				continue;

			for (j = 0; j < PAGELEN; j++) {
				int k;
				for (k = i + 1; k < PROGRAMLEN; k++)
					if (page[j] == program[k]) {
						index[j] = k;// index存的是page中各数第一次出现的下标
						break;
					}
				if (k == PROGRAMLEN)
					index[j] = PROGRAMLEN;
			}

			int suffixOfMax = 0;
			for (j = 1; j < PAGELEN; j++) {
				if (index[j] > index[suffixOfMax])
					suffixOfMax = j;
			}
			page[suffixOfMax] = program[i];
		}

		JOptionPane.showMessageDialog(null, "最佳置换算法（OPT）缺页 " + lostPage + " 次");
	}

}