1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
use super::Weight;
use rand::prelude::{Rng, ThreadRng};
use std::{collections::HashMap, hash::Hash};
#[derive(Clone, Debug)]
struct RandWeightItem<T> {
item: T,
weight: isize,
}
#[derive(Default)]
pub struct RandWeight<T> {
items: Vec<RandWeightItem<T>>,
n: usize,
sum_of_weights: isize,
r: ThreadRng,
}
impl<T: Clone + PartialEq + Eq + Hash> RandWeight<T> {
pub fn new() -> Self {
RandWeight {
items: Vec::new(),
n: 0,
sum_of_weights: 0,
r: rand::thread_rng(),
}
}
}
impl<T: Clone + PartialEq + Eq + Hash> Weight for RandWeight<T> {
type Item = T;
fn next(&mut self) -> Option<T> {
if self.n == 0 {
return None;
}
if self.n == 1 {
return Some(self.items[0].item.clone());
}
let mut index = self.r.gen_range(0, self.sum_of_weights);
for item in &self.items {
index -= item.weight;
if index <= 0 {
return Some(item.item.clone());
}
}
Some(self.items[self.n - 1].item.clone())
}
fn add(&mut self, item: T, weight: isize) {
let weight_item = RandWeightItem { item, weight };
self.items.push(weight_item);
self.n += 1;
self.sum_of_weights += weight;
}
fn all(&self) -> HashMap<T, isize> {
let mut rt: HashMap<T, isize> = HashMap::new();
for w in &self.items {
rt.insert(w.item.clone(), w.weight);
}
rt
}
fn remove_all(&mut self) {
self.items.clear();
self.n = 0;
self.r = rand::thread_rng();
}
fn reset(&mut self) {
self.r = rand::thread_rng();
}
}
#[cfg(test)]
mod tests {
use crate::{RandWeight, Weight};
use std::collections::HashMap;
#[test]
fn test_smooth_weight() {
let mut sw: RandWeight<&str> = RandWeight::new();
sw.add("server1", 5);
sw.add("server2", 2);
sw.add("server3", 3);
let mut results: HashMap<&str, usize> = HashMap::new();
for _ in 0..10000 {
let s = sw.next().unwrap();
*results.entry(s).or_insert(0) += 1;
}
println!("{:?}", results);
}
}