DORGTR (3) Linux Manual Page

dorgtr.f –

Synopsis

Functions/Subroutines

subroutine dorgtr (UPLO, N, A, LDA, TAU, WORK, LWORK, INFO)
DORGTR

Function/Subroutine Documentation

subroutine dorgtr (characterUPLO, integerN, double precision, dimension( lda, * )A, integerLDA, double precision, dimension( * )TAU, double precision, dimension( * )WORK, integerLWORK, integerINFO)

DORGTR

Purpose:

 DORGTR generates a real orthogonal matrix Q which is defined as the

 product of n-1 elementary reflectors of order N, as returned by

 DSYTRD:

 if UPLO = ‘U’, Q = H(n-1) . . . H(2) H(1),

 if UPLO = ‘L’, Q = H(1) H(2) . . . H(n-1).

 

Parameters:

UPLO

 UPLO is CHARACTER*1

 = ‘U’: Upper triangle of A contains elementary reflectors

 from DSYTRD;

 = ‘L’: Lower triangle of A contains elementary reflectors

 from DSYTRD.

N

 N is INTEGER

 The order of the matrix Q. N >= 0.

A

 A is DOUBLE PRECISION array, dimension (LDA,N)

 On entry, the vectors which define the elementary reflectors,

 as returned by DSYTRD.

 On exit, the N-by-N orthogonal matrix Q.

LDA

 LDA is INTEGER

 The leading dimension of the array A. LDA >= max(1,N).

TAU

 TAU is DOUBLE PRECISION array, dimension (N-1)

 TAU(i) must contain the scalar factor of the elementary

 reflector H(i), as returned by DSYTRD.

WORK

 WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK))

 On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

LWORK

 LWORK is INTEGER

 The dimension of the array WORK. LWORK >= max(1,N-1).

 For optimum performance LWORK >= (N-1)*NB, where NB is

 the optimal blocksize.

 If LWORK = -1, then a workspace query is assumed; the routine

 only calculates the optimal size of the WORK array, returns

 this value as the first entry of the WORK array, and no error

 message related to LWORK is issued by XERBLA.

INFO

 INFO is INTEGER

 = 0: successful exit

 < 0: if INFO = -i, the i-th argument had an illegal value

 

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

November 2011

Definition at line 124 of file dorgtr.f.

Author

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