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extern crate num;
extern crate rand;
extern crate utils;
use utils::map_range;
use rand::{Rand, random};
use std::cell::RefCell;
use std::fmt::Debug;
use num::{Float, FromPrimitive};
thread_local!(static MAYBE_NEXT_VALUE: RefCell<Option<f64>> = RefCell::new(None));
#[inline]
fn two<F>() -> F where F: Float { let one: F = F::one(); one + one }
#[inline]
pub fn gen_raw<F>() -> F where F: Float + FromPrimitive + Rand {
MAYBE_NEXT_VALUE.with(|maybe_next_value| {
let maybe_next = *maybe_next_value.borrow();
if let Some(next_value) = maybe_next {
*maybe_next_value.borrow_mut() = None;
FromPrimitive::from_f64(next_value).unwrap()
} else {
let (zero, one, two): (F, F, F) = (F::zero(), F::one(), two::<F>());
let (mut va, mut vb, mut s): (F, F, F) = (zero, zero, zero);
while s >= one || s == zero {
va = two * random::<F>() - one;
vb = two * random::<F>() - one;
s = va * vb + va * vb
};
let multi = ((-two) * s.abs().ln() / s).abs().sqrt();
*maybe_next_value.borrow_mut() = (vb * multi).to_f64();
va * multi
}
})
}
#[inline]
pub fn gen<F>(n: F, randomness: f32) -> F
where F: Float + Rand + FromPrimitive + Debug {
let (zero, one): (F, F) = (F::zero(), F::one());
assert!(n >= zero && n <= one, "Gaussian::gen : given `n` ({:?}) must \
be a percentage between 0 and 1.", n);
let mut ans = gen_raw::<F>()
* FromPrimitive::from_f32(randomness.powf(2.0)).unwrap()
+ (n * two::<F>() - one);
ans = map_range(ans, -one, one, zero, one);
if ans >= one || ans < zero {
gen::<F>(n, randomness)
} else {
ans
}
}
#[inline]
pub fn gen_map<F>(n: F, randomness: f32, min_range: F, max_range: F) -> F
where F: Float + Rand + FromPrimitive + Debug {
let (zero, one): (F, F) = (F::zero(), F::one());
let perc = map_range(n, min_range, max_range, zero, one);
map_range(gen(perc, randomness), zero, one, min_range, max_range)
}