Function score_piece_chunked 

pub fn score_piece_chunked(
    piece: &RecordPiece,
    params: &CurveParams,
    chunk_scores: usize,
) -> PieceCurves

Score a single piece, dividing it into chunks of the given size.

A record is often one enormous piece, so splitting only by piece leaves a chromosome on a single thread. Chunking within the piece both spreads that work and bounds how much of it is in memory at once.