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Diffstat (limited to 'SRC/dlarfg.f')
| -rw-r--r-- | SRC/dlarfg.f | 144 |
1 files changed, 99 insertions, 45 deletions
diff --git a/SRC/dlarfg.f b/SRC/dlarfg.f index a4221e79..fdb1d55e 100644 --- a/SRC/dlarfg.f +++ b/SRC/dlarfg.f @@ -1,9 +1,107 @@ +*> \brief \b DLARFG +* +* =========== DOCUMENTATION =========== +* +* Online html documentation available at +* http://www.netlib.org/lapack/explore-html/ +* +* Definition +* ========== +* +* SUBROUTINE DLARFG( N, ALPHA, X, INCX, TAU ) +* +* .. Scalar Arguments .. +* INTEGER INCX, N +* DOUBLE PRECISION ALPHA, TAU +* .. +* .. Array Arguments .. +* DOUBLE PRECISION X( * ) +* .. +* +* Purpose +* ======= +* +*>\details \b Purpose: +*>\verbatim +*> +*> 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. +*> +*>\endverbatim +* +* Arguments +* ========= +* +*> \param[in] N +*> \verbatim +*> N is INTEGER +*> The order of the elementary reflector. +*> \endverbatim +*> +*> \param[in,out] ALPHA +*> \verbatim +*> ALPHA is DOUBLE PRECISION +*> On entry, the value alpha. +*> On exit, it is overwritten with the value beta. +*> \endverbatim +*> +*> \param[in,out] X +*> \verbatim +*> 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. +*> \endverbatim +*> +*> \param[in] INCX +*> \verbatim +*> INCX is INTEGER +*> The increment between elements of X. INCX > 0. +*> \endverbatim +*> +*> \param[out] TAU +*> \verbatim +*> TAU is DOUBLE PRECISION +*> The value tau. +*> \endverbatim +*> +* +* Authors +* ======= +* +*> \author Univ. of Tennessee +*> \author Univ. of California Berkeley +*> \author Univ. of Colorado Denver +*> \author NAG Ltd. +* +*> \date November 2011 +* +*> \ingroup doubleOTHERauxiliary +* +* ===================================================================== SUBROUTINE DLARFG( N, ALPHA, X, INCX, TAU ) * * -- LAPACK auxiliary routine (version 3.3.1) -- * -- LAPACK is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- -* -- April 2011 -- +* November 2011 * * .. Scalar Arguments .. INTEGER INCX, N @@ -13,50 +111,6 @@ DOUBLE PRECISION X( * ) * .. * -* 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. -* -* Arguments -* ========= -* -* N (input) INTEGER -* The order of the elementary reflector. -* -* ALPHA (input/output) DOUBLE PRECISION -* On entry, the value alpha. -* On exit, it is overwritten with the value beta. -* -* X (input/output) DOUBLE PRECISION 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) DOUBLE PRECISION -* The value tau. -* * ===================================================================== * * .. Parameters .. |