# dorgtr.f(3) [debian man page]

```dorgtr.f(3)							      LAPACK							       dorgtr.f(3)

NAME
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

NAG Ltd.

Date:
November 2011

Definition at line 124 of file dorgtr.f.

Author
Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.1							  Sun May 26 2013						       dorgtr.f(3)```

## Check Out this Related Man Page

```dormtr.f(3)							      LAPACK							       dormtr.f(3)

NAME
dormtr.f -

SYNOPSIS
Functions/Subroutines
subroutine dormtr (SIDE, UPLO, TRANS, M, N, A, LDA, TAU, C, LDC, WORK, LWORK, INFO)
DORMTR

Function/Subroutine Documentation
subroutine dormtr (characterSIDE, characterUPLO, characterTRANS, integerM, integerN, double precision, dimension( lda, * )A, integerLDA, double
precision, dimension( * )TAU, double precision, dimension( ldc, * )C, integerLDC, double precision, dimension( * )WORK, integerLWORK,
integerINFO)
DORMTR

Purpose:

DORMTR overwrites the general real M-by-N matrix C with

SIDE = 'L'	   SIDE = 'R'
TRANS = 'N':      Q * C	     C * Q
TRANS = 'T':      Q**T * C	     C * Q**T

where Q is a real orthogonal matrix of order nq, with nq = m if
SIDE = 'L' and nq = n if SIDE = 'R'. Q is defined as the product of
nq-1 elementary reflectors, as returned by DSYTRD:

if UPLO = 'U', Q = H(nq-1) . . . H(2) H(1);

if UPLO = 'L', Q = H(1) H(2) . . . H(nq-1).

Parameters:
SIDE

SIDE is CHARACTER*1
= 'L': apply Q or Q**T from the Left;
= 'R': apply Q or Q**T from the Right.

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.

TRANS

TRANS is CHARACTER*1
= 'N':  No transpose, apply Q;
= 'T':  Transpose, apply Q**T.

M

M is INTEGER
The number of rows of the matrix C. M >= 0.

N

N is INTEGER
The number of columns of the matrix C. N >= 0.

A

A is DOUBLE PRECISION array, dimension
(LDA,M) if SIDE = 'L'
(LDA,N) if SIDE = 'R'
The vectors which define the elementary reflectors, as
returned by DSYTRD.

LDA

LDA is INTEGER
The leading dimension of the array A.
LDA >= max(1,M) if SIDE = 'L'; LDA >= max(1,N) if SIDE = 'R'.

TAU

TAU is DOUBLE PRECISION array, dimension
(M-1) if SIDE = 'L'
(N-1) if SIDE = 'R'
TAU(i) must contain the scalar factor of the elementary
reflector H(i), as returned by DSYTRD.

C

C is DOUBLE PRECISION array, dimension (LDC,N)
On entry, the M-by-N matrix C.
On exit, C is overwritten by Q*C or Q**T*C or C*Q**T or C*Q.

LDC

LDC is INTEGER
The leading dimension of the array C. LDC >= max(1,M).

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.
If SIDE = 'L', LWORK >= max(1,N);
if SIDE = 'R', LWORK >= max(1,M).
For optimum performance LWORK >= N*NB if SIDE = 'L', and
LWORK >= M*NB if SIDE = 'R', 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

NAG Ltd.

Date:
November 2011

Definition at line 171 of file dormtr.f.

Author
Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.1							  Sun May 26 2013						       dormtr.f(3)```
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