Contents
zungtr - generate a complex unitary matrix Q which is
defined as the product of n-1 elementary reflectors of order
N, as returned by CHETRD
SUBROUTINE ZUNGTR(UPLO, N, A, LDA, TAU, WORK, LWORK, INFO)
CHARACTER * 1 UPLO
DOUBLE COMPLEX A(LDA,*), TAU(*), WORK(*)
INTEGER N, LDA, LWORK, INFO
SUBROUTINE ZUNGTR_64(UPLO, N, A, LDA, TAU, WORK, LWORK, INFO)
CHARACTER * 1 UPLO
DOUBLE COMPLEX A(LDA,*), TAU(*), WORK(*)
INTEGER*8 N, LDA, LWORK, INFO
F95 INTERFACE
SUBROUTINE UNGTR(UPLO, [N], A, [LDA], TAU, [WORK], [LWORK], [INFO])
CHARACTER(LEN=1) :: UPLO
COMPLEX(8), DIMENSION(:) :: TAU, WORK
COMPLEX(8), DIMENSION(:,:) :: A
INTEGER :: N, LDA, LWORK, INFO
SUBROUTINE UNGTR_64(UPLO, [N], A, [LDA], TAU, [WORK], [LWORK], [INFO])
CHARACTER(LEN=1) :: UPLO
COMPLEX(8), DIMENSION(:) :: TAU, WORK
COMPLEX(8), DIMENSION(:,:) :: A
INTEGER(8) :: N, LDA, LWORK, INFO
C INTERFACE
#include <sunperf.h>
void zungtr(char uplo, int n, doublecomplex *a, int lda,
doublecomplex *tau, int *info);
void zungtr_64(char uplo, long n, doublecomplex *a, long
lda, doublecomplex *tau, long *info);
zungtr 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).
UPLO (input)
= 'U': Upper triangle of A contains elementary
reflectors from CHETRD; = 'L': Lower triangle of A
contains elementary reflectors from CHETRD.
N (input) The order of the matrix Q. N >= 0.
A (input/output)
On entry, the vectors which define the elementary
reflectors, as returned by CHETRD. On exit, the
N-by-N unitary matrix Q.
LDA (input)
The leading dimension of the array A. LDA >= N.
TAU (input)
TAU(i) must contain the scalar factor of the ele-
mentary reflector H(i), as returned by CHETRD.
WORK (workspace)
On exit, if INFO = 0, WORK(1) returns the optimal
LWORK.
LWORK (input)
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 (output)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille-
gal value