1use crate::{Infos, Module, VecZnx};
 2use rand_distr::{Distribution, Normal};
 3use sampling::source::Source;
 4
 5pub trait Sampling {
 6    /// Fills the first `cols` cols with uniform values in \[-2^{log_base2k-1}, 2^{log_base2k-1}\]
 7    fn fill_uniform(&self, log_base2k: usize, a: &mut VecZnx, cols: usize, source: &mut Source);
 8
 9    /// Adds vector sampled according to the provided distribution, scaled by 2^{-log_k} and bounded to \[-bound, bound\].
10    fn add_dist_f64<D: Distribution<f64>>(
11        &self,
12        log_base2k: usize,
13        a: &mut VecZnx,
14        log_k: usize,
15        source: &mut Source,
16        dist: D,
17        bound: f64,
18    );
19
20    /// Adds a discrete normal vector scaled by 2^{-log_k} with the provided standard deviation and bounded to \[-bound, bound\].
21    fn add_normal(&self, log_base2k: usize, a: &mut VecZnx, log_k: usize, source: &mut Source, sigma: f64, bound: f64);
22}
23
24impl Sampling for Module {
25    fn fill_uniform(&self, log_base2k: usize, a: &mut VecZnx, cols: usize, source: &mut Source) {
26        let base2k: u64 = 1 << log_base2k;
27        let mask: u64 = base2k - 1;
28        let base2k_half: i64 = (base2k >> 1) as i64;
29        let size: usize = a.n() * cols;
30        a.raw_mut()[..size]
31            .iter_mut()
32            .for_each(|x| *x = (source.next_u64n(base2k, mask) as i64) - base2k_half);
33    }
34
35    fn add_dist_f64<D: Distribution<f64>>(
36        &self,
37        log_base2k: usize,
38        a: &mut VecZnx,
39        log_k: usize,
40        source: &mut Source,
41        dist: D,
42        bound: f64,
43    ) {
44        assert!(
45            (bound.log2().ceil() as i64) < 64,
46            "invalid bound: ceil(log2(bound))={} > 63",
47            (bound.log2().ceil() as i64)
48        );
49
50        let log_base2k_rem: usize = log_k % log_base2k;
51
52        if log_base2k_rem != 0 {
53            a.at_mut(a.cols() - 1).iter_mut().for_each(|a| {
54                let mut dist_f64: f64 = dist.sample(source);
55                while dist_f64.abs() > bound {
56                    dist_f64 = dist.sample(source)
57                }
58                *a += (dist_f64.round() as i64) << log_base2k_rem;
59            });
60        } else {
61            a.at_mut(a.cols() - 1).iter_mut().for_each(|a| {
62                let mut dist_f64: f64 = dist.sample(source);
63                while dist_f64.abs() > bound {
64                    dist_f64 = dist.sample(source)
65                }
66                *a += dist_f64.round() as i64
67            });
68        }
69    }
70
71    fn add_normal(&self, log_base2k: usize, a: &mut VecZnx, log_k: usize, source: &mut Source, sigma: f64, bound: f64) {
72        self.add_dist_f64(
73            log_base2k,
74            a,
75            log_k,
76            source,
77            Normal::new(0.0, sigma).unwrap(),
78            bound,
79        );
80    }
81}