dlarz.f File Reference

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Functions/Subroutines
subroutine	dlarz (SIDE, M, N, L, V, INCV, TAU, C, LDC, WORK)
	DLARZ applies an elementary reflector (as returned by stzrzf) to a general matrix.

---

Function/Subroutine Documentation

subroutine dlarz	(	character	SIDE,
		integer	M,
		integer	N,
		integer	L,
		double precision, dimension( * )	V,
		integer	INCV,
		double precision	TAU,
		double precision, dimension( ldc, * )	C,
		integer	LDC,
		double precision, dimension( * )	WORK
	)

DLARZ applies an elementary reflector (as returned by stzrzf) to a general matrix.

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

Purpose:

 DLARZ applies a real elementary reflector H to a real M-by-N
 matrix C, from either the left or the right. H is represented in the
 form

       H = I - tau * v * v**T

 where tau is a real scalar and v is a real vector.

 If tau = 0, then H is taken to be the unit matrix.


 H is a product of k elementary reflectors as returned by DTZRZF.

Parameters:

[in]	SIDE	SIDE is CHARACTER*1 = 'L': form H * C = 'R': form C * H
[in]	M	M is INTEGER The number of rows of the matrix C.
[in]	N	N is INTEGER The number of columns of the matrix C.
[in]	L	L is INTEGER The number of entries of the vector V containing the meaningful part of the Householder vectors. If SIDE = 'L', M >= L >= 0, if SIDE = 'R', N >= L >= 0.
[in]	V	V is DOUBLE PRECISION array, dimension (1+(L-1)*abs(INCV)) The vector v in the representation of H as returned by DTZRZF. V is not used if TAU = 0.
[in]	INCV	INCV is INTEGER The increment between elements of v. INCV <> 0.
[in]	TAU	TAU is DOUBLE PRECISION The value tau in the representation of H.
[in,out]	C	C is DOUBLE PRECISION array, dimension (LDC,N) On entry, the M-by-N matrix C. On exit, C is overwritten by the matrix H * C if SIDE = 'L', or C * H if SIDE = 'R'.
[in]	LDC	LDC is INTEGER The leading dimension of the array C. LDC >= max(1,M).
[out]	WORK	WORK is DOUBLE PRECISION array, dimension (N) if SIDE = 'L' or (M) if SIDE = 'R'

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Contributors:

A. Petitet, Computer Science Dept., Univ. of Tenn., Knoxville, USA

Further Details:

Definition at line 146 of file dlarz.f.

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