“…A recent direction in numerical computation research pertains to k-tridiagonal matrices [21][22][23][24][25][26][27][28][29], for which, important algorithms, such as block-diagonalization [21], matrix inverse [22,23,26] and singular value decomposition [30], are improved by several orders of magnitude. A k-tridiagonal matrix [22] T ∈ R n×n is a matrix whose elements lay only on its main and kth upper and lower diagonals, i.e., there are some d ∈ R n and a, b ∈ R n−k , such that…”