Decomposition_LU

代码说明：

  将系数矩阵A转变成等价两个矩阵L和U的乘积 ，其中L和U分别是下三角和上三角矩阵。当A的所有顺序主子式都不为0时，矩阵A可以唯一的分解为A=LU。其中L是单位下三角矩阵，U是上三角矩阵。 (The coefficient matrix A into two matrices L and U is equivalent to the product, where L and U are lower triangular and upper triangular matrix. When A master style is not all the sequence is 0, the matrix A can only be decomposed into A = LU. Where L is unit lower triangular matrix, U is upper triangular matrix.)