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Sometimes you need to sample from a set of options. This crate allows you to sample from discrete probability distributions efficiently (O(1) per sample).

It implements a random sampler implementing based on the alias method ( One uses it by passing a vector of probabilites to the constructor. The constructor builds a data structure in O(n*n*log(n)) (Note: It would be quite possible to implement this in O(n*log(n)), however for reasonable sized number of values this method is faster than using the more effictient data strucutres. If the construction is slow in your case, you might consider using min/max heaps insteat of resorting the array after each construction step). This data structure can then be used to to sample a numbers between 0 and n with the corresponding probabilites.

Assume we want to sample from the following distirbution: p(0)=0.5, p(1)=0.3, p(2)=0.1, p(3)=0.1:

extern crate loaded_dice;
extern crate rand;

use loaded_dice::LoadedDiceSampler;
use rand::{thread_rng, Rng};
fn main() {
    let mut s = LoadedDiceSampler::new(vec!(0.5, 0.3, 0.1, 0.1), thread_rng());
    let iter: usize = 100;
    for i in (0..iter) {
        println!("{}", s.sample());