cungtr.f man page

cungtr.f —

Synopsis

Functions/Subroutines

subroutine cungtr (UPLO, N, A, LDA, TAU, WORK, LWORK, INFO)
CUNGTR

Function/Subroutine Documentation

subroutine cungtr (characterUPLO, integerN, complex, dimension( lda, * )A, integerLDA, complex, dimension( * )TAU, complex, dimension( * )WORK, integerLWORK, integerINFO)

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.

Date:

November 2011

Definition at line 124 of file cungtr.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

cungtr(3) is an alias of cungtr.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK