o1_utils/
math.rs

1//! This modules implements some math helper functions.
2
3/// Returns ceil(log2(d)) but panics if d = 0.
4pub fn ceil_log2(d: usize) -> usize {
5    // NOTE: should this really be usize, since usize is depended on the underlying system architecture?
6
7    assert!(d != 0);
8    let mut pow2 = 1;
9    let mut ceil_log2 = 0;
10    while d > pow2 {
11        ceil_log2 += 1;
12        pow2 = match pow2.checked_mul(2) {
13            Some(x) => x,
14            None => break,
15        }
16    }
17    ceil_log2
18}
19
20/// This function is bound to be stable soon. See <https://github.com/rust-lang/rust/issues/88581>
21pub fn div_ceil(a: usize, b: usize) -> usize {
22    (a + b - 1) / b
23}
o1_utils/math.rs

o1_utils/
math.rs
