    
    worker.scope(indexes.len(), |scope, chunk| {
        for (idx, fe) in indexes.chunks(chunk)
                .zip(result.chunks_mut(chunk)) {
            scope.spawn(move |_| {
                let mut repr = F::zero().into_repr();
                for (idx, fe) in idx.iter().zip(fe.iter_mut()) {
                    repr.as_mut()[0] = *idx as u64;