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// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Sampling from random distributions.
//!
//! This is a generalization of `Rand` to allow parameters to control the
//! exact properties of the generated values, e.g. the mean and standard
//! deviation of a normal distribution. The `Sample` trait is the most
//! general, and allows for generating values that change some state
//! internally. The `IndependentSample` trait is for generating values
//! that do not need to record state.
pub use rand4::distributions::Range;
pub use rand4::distributions::{Gamma, ChiSquared, FisherF, StudentT};
pub use rand4::distributions::{Normal, LogNormal};
pub use rand4::distributions::Exp;
pub use rand4::distributions::{range, gamma, normal, exponential};
pub use rand4::distributions::{Sample, IndependentSample, RandSample};
pub use rand4::distributions::{Weighted, WeightedChoice};
#[cfg(test)]
mod tests {
use {Rng, Rand};
use super::{RandSample, WeightedChoice, Weighted, Sample, IndependentSample};
#[derive(PartialEq, Debug)]
struct ConstRand(usize);
impl Rand for ConstRand {
fn rand<R: Rng>(_: &mut R) -> ConstRand {
ConstRand(0)
}
}
// 0, 1, 2, 3, ...
struct CountingRng { i: u32 }
impl Rng for CountingRng {
fn next_u32(&mut self) -> u32 {
self.i += 1;
self.i - 1
}
fn next_u64(&mut self) -> u64 {
self.next_u32() as u64
}
}
#[test]
fn test_rand_sample() {
let mut rand_sample = RandSample::<ConstRand>::new();
assert_eq!(rand_sample.sample(&mut ::test::rng()), ConstRand(0));
assert_eq!(rand_sample.ind_sample(&mut ::test::rng()), ConstRand(0));
}
#[test]
fn test_weighted_choice() {
// this makes assumptions about the internal implementation of
// WeightedChoice, specifically: it doesn't reorder the items,
// it doesn't do weird things to the RNG (so 0 maps to 0, 1 to
// 1, internally; modulo a modulo operation).
macro_rules! t {
($items:expr, $expected:expr) => {{
let mut items = $items;
let wc = WeightedChoice::new(&mut items);
let expected = $expected;
let mut rng = CountingRng { i: 0 };
for &val in expected.iter() {
assert_eq!(wc.ind_sample(&mut rng), val)
}
}}
}
t!(vec!(Weighted { weight: 1, item: 10}), [10]);
// skip some
t!(vec!(Weighted { weight: 0, item: 20},
Weighted { weight: 2, item: 21},
Weighted { weight: 0, item: 22},
Weighted { weight: 1, item: 23}),
[21,21, 23]);
// different weights
t!(vec!(Weighted { weight: 4, item: 30},
Weighted { weight: 3, item: 31}),
[30,30,30,30, 31,31,31]);
// check that we're binary searching
// correctly with some vectors of odd
// length.
t!(vec!(Weighted { weight: 1, item: 40},
Weighted { weight: 1, item: 41},
Weighted { weight: 1, item: 42},
Weighted { weight: 1, item: 43},
Weighted { weight: 1, item: 44}),
[40, 41, 42, 43, 44]);
t!(vec!(Weighted { weight: 1, item: 50},
Weighted { weight: 1, item: 51},
Weighted { weight: 1, item: 52},
Weighted { weight: 1, item: 53},
Weighted { weight: 1, item: 54},
Weighted { weight: 1, item: 55},
Weighted { weight: 1, item: 56}),
[50, 51, 52, 53, 54, 55, 56]);
}
#[test]
fn test_weighted_clone_initialization() {
let initial : Weighted<u32> = Weighted {weight: 1, item: 1};
let clone = initial.clone();
assert_eq!(initial.weight, clone.weight);
assert_eq!(initial.item, clone.item);
}
#[test] #[should_panic]
fn test_weighted_clone_change_weight() {
let initial : Weighted<u32> = Weighted {weight: 1, item: 1};
let mut clone = initial.clone();
clone.weight = 5;
assert_eq!(initial.weight, clone.weight);
}
#[test] #[should_panic]
fn test_weighted_clone_change_item() {
let initial : Weighted<u32> = Weighted {weight: 1, item: 1};
let mut clone = initial.clone();
clone.item = 5;
assert_eq!(initial.item, clone.item);
}
#[test] #[should_panic]
fn test_weighted_choice_no_items() {
WeightedChoice::<isize>::new(&mut []);
}
#[test] #[should_panic]
fn test_weighted_choice_zero_weight() {
WeightedChoice::new(&mut [Weighted { weight: 0, item: 0},
Weighted { weight: 0, item: 1}]);
}
#[test] #[should_panic]
fn test_weighted_choice_weight_overflows() {
let x = ::std::u32::MAX / 2; // x + x + 2 is the overflow
WeightedChoice::new(&mut [Weighted { weight: x, item: 0 },
Weighted { weight: 1, item: 1 },
Weighted { weight: x, item: 2 },
Weighted { weight: 1, item: 3 }]);
}
}