extern crate num_cpus;
extern crate rand;
use crate::*;
#[derive(Debug, Clone)]
pub struct Log2Cache {
log2n: Vec<f64>,
nlog2n: Vec<f64>,
nlog2n_difference: Vec<f64>,
}
impl Log2Cache {
pub fn new(n: usize) -> Self {
let mut log2n = Vec::with_capacity(n + 1);
let mut nlog2n = Vec::with_capacity(n + 1);
let mut nlog2n_difference = Vec::with_capacity(n);
log2n.push(0.0);
nlog2n.push(0.0);
for i in 1..=n {
let i = i as f64;
let log2i = i.log2();
log2n.push(log2i);
let ilog2i = i * log2i;
let ilog2i_last = *nlog2n.last().unwrap();
nlog2n.push(ilog2i);
nlog2n_difference.push(ilog2i - ilog2i_last);
}
Self {
log2n,
nlog2n,
nlog2n_difference,
}
}
pub fn plog2p(&self, x: CountType, n: CountType) -> f64 {
let p = (x as f64) / (n as f64);
let log2p = unsafe {
*self.log2n.get_unchecked(x as usize) - *self.log2n.get_unchecked(n as usize)
};
p * log2p
}
pub fn nlog2n(&self, n: CountType) -> f64 {
unsafe { *self.nlog2n.get_unchecked(n as usize) }
}
pub fn nlog2n_difference(&self, n: CountType) -> f64 {
unsafe { *self.nlog2n_difference.get_unchecked(n as usize) }
}
}