o1_utils/math.rs
1//! This modules implements some math helper functions.
2
3/// Returns ceil(log2(d)) but panics if d = 0.
4///
5/// # Panics
6///
7/// Panics if `d` is 0.
8#[must_use]
9pub fn ceil_log2(d: usize) -> usize {
10 // NOTE: should this really be usize, since usize is depended on the underlying system architecture?
11
12 assert!(d != 0);
13 let mut pow2 = 1;
14 let mut ceil_log2 = 0;
15 while d > pow2 {
16 ceil_log2 += 1;
17 pow2 = match pow2.checked_mul(2) {
18 Some(x) => x,
19 None => break,
20 }
21 }
22 ceil_log2
23}