Doolittle分解，Q=L*R,L是单位下三角；UDU 分解,U是单位上三角阵.Doolittle分解，Q=L*R,L是单位下三角；LDL 分解,L是单位下三角阵(下*对*上)-Doolittle decomposition Q = L* R, L is unit lower triangular　UDU ' decomposition, U is the unit upper triangular matrix. Doolittle, decomposition, Q = L* R, L is unit lower triangular　LDL'　decomposition, L is unit lower triangular array (the* to*)