This operation updates matrix *A* by one of
the following

Matrix *A* is of dimension and vectors
*x* and *y* are of
length *n* .
Matrices
*L* and *U* indicate the lower and upper triangular part of matrix *A* ,
respectively.
the upper- and strictly upper triangular part of matrix *A* , respectively.
We indicate the lower and upper triangular part of matrix by
and
, respectively.