slarz(3P) Sun Performance Library slarz(3P)NAMEslarz - applies 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 * 1 SIDE
INTEGER M, N, L, INCV, LDC
REAL TAU
REAL V(*), C(LDC,*), WORK(*)
SUBROUTINE SLARZ_64(SIDE, M, N, L, V, INCV, TAU, C, LDC, WORK)
CHARACTER * 1 SIDE
INTEGER*8 M, N, L, INCV, LDC
REAL TAU
REAL V(*), C(LDC,*), WORK(*)
F95 INTERFACE
SUBROUTINE LARZ(SIDE, [M], [N], L, V, [INCV], TAU, C, [LDC], [WORK])
CHARACTER(LEN=1) :: SIDE
INTEGER :: M, N, L, INCV, LDC
REAL :: TAU
REAL, DIMENSION(:) :: V, WORK
REAL, DIMENSION(:,:) :: C
SUBROUTINE LARZ_64(SIDE, [M], [N], L, V, [INCV], TAU, C, [LDC], [WORK])
CHARACTER(LEN=1) :: SIDE
INTEGER(8) :: M, N, L, INCV, LDC
REAL :: TAU
REAL, DIMENSION(:) :: V, WORK
REAL, DIMENSION(:,:) :: C
C INTERFACE
#include <sunperf.h>
void slarz(char side, int m, int n, int l, float *v, int incv, float
tau, float *c, int ldc);
void slarz_64(char side, long m, long n, long l, float *v, long incv,
float tau, float *c, long ldc);
PURPOSEslarz 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)
= 'L': form H * C
= 'R': form C * H
M (input) The number of rows of the matrix C.
N (input) The number of columns of the matrix C.
L (input) The number of entries of the vector V containing the meaningā
ful part of the Householder vectors. If SIDE = 'L', M >= L
>= 0, if SIDE = 'R', N >= L >= 0.
V (input) REAL array of 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)
The increment between elements of v. INCV <> 0.
TAU (input)
The value tau in the representation of H.
C (input/output)
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)
The leading dimension of the array C. LDC >= max(1,M).
WORK (workspace)
(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
6 Mar 2009 slarz(3P)