cungtr(3P) Sun Performance Library cungtr(3P)NAMEcungtr - generate a complex unitary matrix Q which is defined as the
product of n-1 elementary reflectors of order N, as returned by CHETRD
SYNOPSIS
SUBROUTINE CUNGTR(UPLO, N, A, LDA, TAU, WORK, LWORK, INFO)
CHARACTER * 1 UPLO
COMPLEX A(LDA,*), TAU(*), WORK(*)
INTEGER N, LDA, LWORK, INFO
SUBROUTINE CUNGTR_64(UPLO, N, A, LDA, TAU, WORK, LWORK, INFO)
CHARACTER * 1 UPLO
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, DIMENSION(:) :: TAU, WORK
COMPLEX, DIMENSION(:,:) :: A
INTEGER :: N, LDA, LWORK, INFO
SUBROUTINE UNGTR_64(UPLO, [N], A, [LDA], TAU, [WORK], [LWORK], [INFO])
CHARACTER(LEN=1) :: UPLO
COMPLEX, DIMENSION(:) :: TAU, WORK
COMPLEX, DIMENSION(:,:) :: A
INTEGER(8) :: N, LDA, LWORK, INFO
C INTERFACE
#include <sunperf.h>
void cungtr(char uplo, int n, complex *a, int lda, complex *tau, int
*info);
void cungtr_64(char uplo, long n, complex *a, long lda, complex *tau,
long *info);
PURPOSEcungtr 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).
ARGUMENTS
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 elementary
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 block‐
size.
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 illegal value
6 Mar 2009 cungtr(3P)
