SLARFG(3F) SLARFG(3F)
SLARFG - generate a real elementary reflector H of order n, such that H
* ( alpha ) = ( beta ), H' * H = I
SUBROUTINE SLARFG( N, ALPHA, X, INCX, TAU )
INTEGER INCX, N
REAL ALPHA, TAU
REAL X( * )
SLARFG generates a real elementary reflector H of order n, such that
( x ) ( 0 )
where alpha and beta are scalars, and x is an (n-1)-element real vector.
H is represented in the form
H = I - tau * ( 1 ) * ( 1 v' ) ,
( v )
where tau is a real scalar and v is a real (n-1)-element
vector.
If the elements of x are all zero, then tau = 0 and H is taken to be the
unit matrix.
Otherwise 1 <= tau <= 2.
N (input) INTEGER
The order of the elementary reflector.
ALPHA (input/output) REAL
On entry, the value alpha. On exit, it is overwritten with the
value beta.
X (input/output) REAL array, dimension
(1+(N-2)*abs(INCX)) On entry, the vector x. On exit, it is
overwritten with the vector v.
INCX (input) INTEGER
The increment between elements of X. INCX > 0.
TAU (output) REAL
The value tau.
SLARFG(3F) SLARFG(3F)
SLARFG - generate a real elementary reflector H of order n, such that H
* ( alpha ) = ( beta ), H' * H = I
SUBROUTINE SLARFG( N, ALPHA, X, INCX, TAU )
INTEGER INCX, N
REAL ALPHA, TAU
REAL X( * )
SLARFG generates a real elementary reflector H of order n, such that
( x ) ( 0 )
where alpha and beta are scalars, and x is an (n-1)-element real vector.
H is represented in the form
H = I - tau * ( 1 ) * ( 1 v' ) ,
( v )
where tau is a real scalar and v is a real (n-1)-element
vector.
If the elements of x are all zero, then tau = 0 and H is taken to be the
unit matrix.
Otherwise 1 <= tau <= 2.
N (input) INTEGER
The order of the elementary reflector.
ALPHA (input/output) REAL
On entry, the value alpha. On exit, it is overwritten with the
value beta.
X (input/output) REAL array, dimension
(1+(N-2)*abs(INCX)) On entry, the vector x. On exit, it is
overwritten with the vector v.
INCX (input) INTEGER
The increment between elements of X. INCX > 0.
TAU (output) REAL
The value tau.
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