SLARZ(3S)SLARZ(3S)NAME
SLARZ - applie a real elementary reflector H to a real M-by-N matrix C,
from either the left or the right
SYNOPSIS
SUBROUTINE SLARZ( SIDE, M, N, L, V, INCV, TAU, C, LDC, WORK )
CHARACTER SIDE
INTEGER INCV, L, LDC, M, N
REAL TAU
REAL C( LDC, * ), V( * ), WORK( * )
IMPLEMENTATION
These routines are part of the SCSL Scientific Library and can be loaded
using either the -lscs or the -lscs_mp option. The -lscs_mp option
directs the linker to use the multi-processor version of the library.
When linking to SCSL with -lscs or -lscs_mp, the default integer size is
4 bytes (32 bits). Another version of SCSL is available in which integers
are 8 bytes (64 bits). This version allows the user access to larger
memory sizes and helps when porting legacy Cray codes. It can be loaded
by using the -lscs_i8 option or the -lscs_i8_mp option. A program may use
only one of the two versions; 4-byte integer and 8-byte integer library
calls cannot be mixed.
PURPOSE
SLARZ 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'
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 STZRZF.
ARGUMENTS
SIDE (input) CHARACTER*1
= 'L': form H * C
= 'R': form C * H
M (input) INTEGER
The number of rows of the matrix C.
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SLARZ(3S)SLARZ(3S)
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) REAL array, dimension (1+(L-1)*abs(INCV))
The vector v in the representation of H as returned by STZRZF. V
is not used if TAU = 0.
INCV (input) INTEGER
The increment between elements of v. INCV <> 0.
TAU (input) REAL
The value tau in the representation of H.
C (input/output) REAL 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) REAL 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
SEE ALSOINTRO_LAPACK(3S), INTRO_SCSL(3S)
This man page is available only online.
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