 We consider contiguous partitions, where the  rows (or columns) of a sparse matrix with N nonzeros are split into K parts without reordering.
<meaning-changed>  We consider contiguous partitions, where the  rows (or columns) of a sparse matrix with N nonzeros are split into K parts without reordering.
 We consider contiguous partitions, where the m rows (or columns) of a sparse matrix with N nonzeros are split into K parts without reordering.