CUNGTR (3) Linux Manual 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
N
= ‘U’: Upper triangle of A contains elementary reflectors
from CHETRD;
= ‘L’: Lower triangle of A contains elementary reflectors
from CHETRD.N is INTEGER
A
The order of the matrix Q. N >= 0.A is COMPLEX array, dimension (LDA,N)
LDA
On entry, the vectors which define the elementary reflectors,
as returned by CHETRD.
On exit, the N-by-N unitary matrix Q.LDA is INTEGER
TAU
The leading dimension of the array A. LDA >= N.TAU is COMPLEX array, dimension (N-1)
WORK
TAU(i) must contain the scalar factor of the elementary
reflector H(i), as returned by CHETRD.WORK is COMPLEX array, dimension (MAX(1,LWORK))
LWORK
On exit, if INFO = 0, WORK(1) returns the optimal LWORK.LWORK is INTEGER
INFO
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 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.