Provided by: liblapack-doc_3.12.0-3build1_all 
NAME
ungtr - {un,or}gtr: generate Q from hetrd
SYNOPSIS
Functions
subroutine cungtr (uplo, n, a, lda, tau, work, lwork, info)
CUNGTR
subroutine dorgtr (uplo, n, a, lda, tau, work, lwork, info)
DORGTR
subroutine sorgtr (uplo, n, a, lda, tau, work, lwork, info)
SORGTR
subroutine zungtr (uplo, n, a, lda, tau, work, lwork, info)
ZUNGTR
Detailed Description
Function Documentation
subroutine cungtr (character uplo, integer n, complex, dimension( lda, * ) a, integer lda,
complex, dimension( * ) tau, complex, dimension( * ) work, integer lwork, integer info)
CUNGTR
Purpose:
CUNGTR generates a complex unitary matrix Q which is defined as the
product of n-1 elementary reflectors of order N, as returned by
CHETRD:
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 CHETRD;
= 'L': Lower triangle of A contains elementary reflectors
from CHETRD.
N
N is INTEGER
The order of the matrix Q. N >= 0.
A
A is COMPLEX array, dimension (LDA,N)
On entry, the vectors which define the elementary reflectors,
as returned by CHETRD.
On exit, the N-by-N unitary matrix Q.
LDA
LDA is INTEGER
The leading dimension of the array A. LDA >= N.
TAU
TAU is COMPLEX array, dimension (N-1)
TAU(i) must contain the scalar factor of the elementary
reflector H(i), as returned by CHETRD.
WORK
WORK is COMPLEX 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 >= 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.
subroutine dorgtr (character uplo, integer n, double precision, dimension( lda, * ) a, integer
lda, double precision, dimension( * ) tau, double precision, dimension( * ) work, integer
lwork, integer info)
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.
subroutine sorgtr (character uplo, integer n, real, dimension( lda, * ) a, integer lda, real,
dimension( * ) tau, real, dimension( * ) work, integer lwork, integer info)
SORGTR
Purpose:
SORGTR generates a real orthogonal matrix Q which is defined as the
product of n-1 elementary reflectors of order N, as returned by
SSYTRD:
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 SSYTRD;
= 'L': Lower triangle of A contains elementary reflectors
from SSYTRD.
N
N is INTEGER
The order of the matrix Q. N >= 0.
A
A is REAL array, dimension (LDA,N)
On entry, the vectors which define the elementary reflectors,
as returned by SSYTRD.
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 REAL array, dimension (N-1)
TAU(i) must contain the scalar factor of the elementary
reflector H(i), as returned by SSYTRD.
WORK
WORK is REAL 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.
subroutine zungtr (character uplo, integer n, complex*16, dimension( lda, * ) a, integer lda,
complex*16, dimension( * ) tau, complex*16, dimension( * ) work, integer lwork, integer
info)
ZUNGTR
Purpose:
ZUNGTR generates a complex unitary matrix Q which is defined as the
product of n-1 elementary reflectors of order N, as returned by
ZHETRD:
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 ZHETRD;
= 'L': Lower triangle of A contains elementary reflectors
from ZHETRD.
N
N is INTEGER
The order of the matrix Q. N >= 0.
A
A is COMPLEX*16 array, dimension (LDA,N)
On entry, the vectors which define the elementary reflectors,
as returned by ZHETRD.
On exit, the N-by-N unitary matrix Q.
LDA
LDA is INTEGER
The leading dimension of the array A. LDA >= N.
TAU
TAU is COMPLEX*16 array, dimension (N-1)
TAU(i) must contain the scalar factor of the elementary
reflector H(i), as returned by ZHETRD.
WORK
WORK is COMPLEX*16 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 >= 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.
Author
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