1 public class PercolationStats {
2
3 private int N;
4 private int T;
5 private double[] results;
6
7 public PercolationStats(int N, int T) {
8 if (N <= 0 || T <= 0) {
9 throw new java.lang.IllegalArgumentException(
10 "N or T must be greater than 0");
11 }
12
13 this.N = N;
14 this.T = T;
15 results = new double[T];
16
17 for (int t = 0; t < T; t++) {
18 results[t] = run();
19 }
20 }
21
22 private double run() {
23 Percolation percolation = new Percolation(N);
24 double count = 0;
25
26 while (!percolation.percolates()) {
27 count++;
28
29 // pick a random site
30 // (N+1 because second value to uniform is exclusive)
31 int i = StdRandom.uniform(1, N + 1);
32 int j = StdRandom.uniform(1, N + 1);
33
34 // generate new random sites until a blocked one is found
35 while (percolation.isOpen(i, j)) {
36
37 i = StdRandom.uniform(1, N + 1);
38 j = StdRandom.uniform(1, N + 1);
39
40 }
41
42 // open that site
43 percolation.open(i, j);
44
45 }
46 return count / (N * N); // percolation threshold estimate
47 }
48
49 public double mean() {
50 return StdStats.mean(results);
51 }
52
53 public double stddev() {
54 return StdStats.stddev(results);
55 }
56
57 public double confidenceHi() {
58 return mean() - 1.96 * stddev() / Math.sqrt(T);
59 }
60
61 public double confidenceLo() {
62 return mean() + 1.96 * stddev() / Math.sqrt(T);
63 }
64
65 public static void main(String[] args) {
66
67 int N;
68 int T;
69
70 if (args.length == 0) {
71 N = 100;
72 T = 10;
73 } else {
74 N = Integer.parseInt(args[0]);
75 T = Integer.parseInt(args[1]);
76 }
77
78 // double startTime = System.nanoTime();
79 PercolationStats stats = new PercolationStats(N, T);
80
81 double confidenceLow = stats.confidenceHi();
82 double confidenceHigh = stats.confidenceLo();
83
84 System.out.println("mean = " + stats.mean());
85 System.out.println("stddev = " + stats.stddev());
86 System.out.println("95% confidence interval = " + confidenceLow + ", "
87 + confidenceHigh);
88
89 // performance measuring
90 // double endTime = System.nanoTime();
91 // System.out.println("time cost: " + (endTime - startTime));
92
93 }
94 }
