subroutine dlarfg (N, ALPHA, X, INCX, TAU)
DLARFG generates an elementary reflector (Householder matrix).
DLARFG generates an elementary reflector (Householder matrix).
Purpose:
DLARFG generates a real elementary reflector H of order n, such that H * ( alpha ) = ( beta ), H**T * H = I. ( 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**T ) , ( 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.
Parameters:
N is INTEGER The order of the elementary reflector.
ALPHA
ALPHA is DOUBLE PRECISION On entry, the value alpha. On exit, it is overwritten with the value beta.
X
X is DOUBLE PRECISION array, dimension (1+(N-2)*abs(INCX)) On entry, the vector x. On exit, it is overwritten with the vector v.
INCX
INCX is INTEGER The increment between elements of X. INCX > 0.
TAU
TAU is DOUBLE PRECISION The value tau.
Author:
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
Definition at line 108 of file dlarfg.f.
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