slarfg.f File Reference

Functions/Subroutines
subroutine	slarfg (n, alpha, x, incx, tau)
	SLARFG

Function/Subroutine Documentation

slarfg()

subroutine slarfg	(	integer	n,
		real	alpha,
		real, dimension( * )	x,
		integer	incx,
		real	tau
	)

SLARFG

Download SLARFG + dependencies [TGZ] [ZIP] [TXT]

Purpose:

 SLARFG 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

[in]	N	N is INTEGER The order of the elementary reflector.
[in,out]	ALPHA	ALPHA is REAL On entry, the value alpha. On exit, it is overwritten with the value beta.
[in,out]	X	X is REAL array, dimension (1+(N-2)*abs(INCX)) On entry, the vector x. On exit, it is overwritten with the vector v.
[in]	INCX	INCX is INTEGER The increment between elements of X. INCX > 0.
[out]	TAU	TAU is REAL The value tau.

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date

November 2011