slarfg.f File Reference

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Functions/Subroutines
subroutine	SLARFG (N, ALPHA, X, INCX, TAU)
	SLARFG

---

Function/Subroutine Documentation

subroutine SLARFG	(	INTEGER	N,
		REAL	ALPHA,
		REAL, dimension( * )	X,
		INTEGER	INCX,
		REAL	TAU
	)

SLARFG

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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

Definition at line 107 of file slarfg.f.

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