DLARZ
Purpose
DLARZ applies a real elementary reflector H to a real M-by-N
matrix C, from either the left or the right. H is represented in the
form
H = I - tau * v * v**T
where tau is a real scalar and v is a real vector.
If tau = 0, then H is taken to be the unit matrix.
H is a product of k elementary reflectors as returned by DTZRZF.
matrix C, from either the left or the right. H is represented in the
form
H = I - tau * v * v**T
where tau is a real scalar and v is a real vector.
If tau = 0, then H is taken to be the unit matrix.
H is a product of k elementary reflectors as returned by DTZRZF.
Arguments
| SIDE |
(input) CHARACTER*1
= 'L': form H * C
= 'R': form C * H |
| M |
(input) INTEGER
The number of rows of the matrix C.
|
| N |
(input) INTEGER
The number of columns of the matrix C.
|
| L |
(input) INTEGER
The number of entries of the vector V containing
the meaningful part of the Householder vectors. If SIDE = 'L', M >= L >= 0, if SIDE = 'R', N >= L >= 0. |
| V |
(input) DOUBLE PRECISION array, dimension (1+(L-1)*abs(INCV))
The vector v in the representation of H as returned by
DTZRZF. V is not used if TAU = 0. |
| INCV |
(input) INTEGER
The increment between elements of v. INCV <> 0.
|
| TAU |
(input) DOUBLE PRECISION
The value tau in the representation of H.
|
| C |
(input/output) DOUBLE PRECISION array, dimension (LDC,N)
On entry, the M-by-N matrix C.
On exit, C is overwritten by the matrix H * C if SIDE = 'L', or C * H if SIDE = 'R'. |
| LDC |
(input) INTEGER
The leading dimension of the array C. LDC >= max(1,M).
|
| WORK |
(workspace) DOUBLE PRECISION array, dimension
(N) if SIDE = 'L'
or (M) if SIDE = 'R' |
Further Details
Based on contributions by
A. Petitet, Computer Science Dept., Univ. of Tenn., Knoxville, USA
A. Petitet, Computer Science Dept., Univ. of Tenn., Knoxville, USA