Purpose
To apply a real elementary reflector H to a real m-by-(n+1)
matrix C = [ A B ], from the right, where A has one column. H is
represented in the form
( 1 )
H = I - tau * u *u', u = ( ),
( v )
where tau is a real scalar and v is a real n-vector.
If tau = 0, then H is taken to be the unit matrix.
In-line code is used if H has order < 11.
Specification
SUBROUTINE MB04NY( M, N, V, INCV, TAU, A, LDA, B, LDB, DWORK )
C .. Scalar Arguments ..
INTEGER INCV, LDA, LDB, M, N
DOUBLE PRECISION TAU
C .. Array Arguments ..
DOUBLE PRECISION A( LDA, * ), B( LDB, * ), DWORK( * ), V( * )
Arguments
Input/Output Parameters
M (input) INTEGER
The number of rows of the matrices A and B. M >= 0.
N (input) INTEGER
The number of columns of the matrix B. N >= 0.
V (input) DOUBLE PRECISION array, dimension
(1+(N-1)*ABS( INCV ))
The vector v in the representation of H.
INCV (input) INTEGER
The increment between the elements of v. INCV <> 0.
TAU (input) DOUBLE PRECISION
The scalar factor of the elementary reflector H.
A (input/output) DOUBLE PRECISION array, dimension (LDA,1)
On entry, the leading M-by-1 part of this array must
contain the matrix A.
On exit, the leading M-by-1 part of this array contains
the updated matrix A (the first column of C * H).
LDA INTEGER
The leading dimension of array A. LDA >= MAX(1,M).
B (input/output) DOUBLE PRECISION array, dimension (LDB,N)
On entry, the leading M-by-N part of this array must
contain the matrix B.
On exit, the leading M-by-N part of this array contains
the updated matrix B (the last n columns of C * H).
LDB INTEGER
The leading dimension of array B. LDB >= MAX(1,M).
Workspace
DWORK DOUBLE PRECISION array, dimension (M)
DWORK is not referenced if H has order less than 11.
Method
The routine applies the elementary reflector H, taking the special structure of C into account.Numerical Aspects
The algorithm is backward stable.Further Comments
NoneExample
Program Text
NoneProgram Data
NoneProgram Results
None