Function attn_held_bytes 

pub fn attn_held_bytes(g: usize, vd: usize, splits: usize, acc: usize) -> usize

The bytes of a block’s g heads’ partials over splits chunks — each chunk’s maximum, sum and vd weighed values, in the accumulator’s acc bytes — and whether the block holds them (held): a row cut into chunks, the partials within ATTN_HELD_BYTES.