dorghr.f (3) Linux Manual Page

dorghr.f –

Synopsis

Functions/Subroutines

subroutine dorghr (N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO)
DORGHR

Function/Subroutine Documentation

subroutine dorghr (integerN, integerILO, integerIHI, double precision, dimension( lda, * )A, integerLDA, double precision, dimension( * )TAU, double precision, dimension( * )WORK, integerLWORK, integerINFO)

DORGHR

Purpose:

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

 product of IHI-ILO elementary reflectors of order N, as returned by

 DGEHRD:

 Q = H(ilo) H(ilo+1) . . . H(ihi-1).

 

Parameters:

N

 N is INTEGER

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

ILO

 ILO is INTEGER

IHI

 IHI is INTEGER

 ILO and IHI must have the same values as in the previous call

 of DGEHRD. Q is equal to the unit matrix except in the

 submatrix Q(ilo+1:ihi,ilo+1:ihi).

 1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.

A

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

 On entry, the vectors which define the elementary reflectors,

 as returned by DGEHRD.

 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 DGEHRD.

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 >= IHI-ILO.

 For optimum performance LWORK >= (IHI-ILO)*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 127 of file dorghr.f.

Author

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