SRC/dlarz.f(3) | Library Functions Manual | SRC/dlarz.f(3) |
NAME
SRC/dlarz.f
SYNOPSIS
Functions/Subroutines
subroutine dlarz (side, m, n, l, v, incv, tau, c, ldc,
work)
DLARZ applies an elementary reflector (as returned by stzrzf) to a
general matrix.
Function/Subroutine Documentation
subroutine dlarz (character side, integer m, integer n, integer l, double precision, dimension( * ) v, integer incv, double precision tau, double precision, dimension( ldc, * ) c, integer ldc, double precision, dimension( * ) work)
DLARZ applies an elementary reflector (as returned by stzrzf) to a general matrix.
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.
Parameters
SIDE
SIDE is CHARACTER*1 = 'L': form H * C = 'R': form C * H
M
M is INTEGER The number of rows of the matrix C.
N
N is INTEGER The number of columns of the matrix C.
L
L is 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
V is 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
INCV is INTEGER The increment between elements of v. INCV <> 0.
TAU
TAU is DOUBLE PRECISION The value tau in the representation of H.
C
C is 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
LDC is INTEGER The leading dimension of the array C. LDC >= max(1,M).
WORK
WORK is DOUBLE PRECISION array, dimension (N) if SIDE = 'L' or (M) if SIDE = 'R'
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Contributors:
A. Petitet, Computer Science Dept., Univ. of Tenn.,
Knoxville, USA
Further Details:
Definition at line 144 of file dlarz.f.
Author
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