系統設計

1class LamportClock {
2  time = 0;
3 
4  tick(): number {                       // a local event or a send
5    this.time += 1;
6    return this.time;
7  }
8 
9  receive(stamp: number): number {
10    this.time = Math.max(this.time, stamp) + 1;
11    return this.time;
12  }
13}
14 
15class VectorClock {
16  v: number[];
17  constructor(private me: number, processes: number) {
18    this.v = new Array(processes).fill(0);
19  }
20 
21  tick(): number[] {                     // a local event or a send
22    this.v[this.me] += 1;
23    return [...this.v];                  // a send carries this copy
24  }
25 
26  receive(stamp: number[]): number[] {
27    for (let i = 0; i < this.v.length; i++) {
28      this.v[i] = Math.max(this.v[i], stamp[i]);
29    }
30    this.v[this.me] += 1;
31    return [...this.v];
32  }
33}
34 
35// "before": a happened before b. "concurrent": neither saw the other.
36function compare(a: number[], b: number[]): string {
37  let less = false, more = false;
38  for (let i = 0; i < a.length; i++) {
39    if (a[i] < b[i]) less = true;
40    if (a[i] > b[i]) more = true;
41  }
42  if (less && !more) return "before";
43  if (more && !less) return "after";
44  return less ? "concurrent" : "equal";
45}