message: add doc  comment
diff: -/// Returns ceil(log2(d)) but panics if d = 0.
  +//! This modules implements some math helper functions.
  -// NOTE: should this really be usize, since usize is depended on the underlying system architecture?
  +/// Returns ceil(log2(d)) but panics if d = 0.
  pub fn ceil_log2(d: usize) -> usize {
  + // NOTE: should this really be usize, since usize is depended on the underlying system architecture?
  +
  assert!(d != 0);
  let mut pow2 = 1;
  let mut ceil_log2 = 0;
  