Function range_even 

pub fn range_even(
    total: usize,
    worker_index: u16,
    worker_count: u16,
) -> Result<Range<usize>, UnevenError>

Strict even-split variant of range.

Returns Ok(slice) — identical to range(total, worker_index, worker_count) — when total % worker_count == 0, so every worker owns exactly the same number of items. Returns UnevenError otherwise.

Use this when your algorithm genuinely requires an even split (e.g. SIMD kernels that assume a fixed per-worker tile size) and you would rather fail loudly than silently process an uneven distribution. For workloads that can absorb a one-item skew — histograms, reductions, map-style passes — prefer range.