cungtr - 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 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
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
#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);
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).
= 'U': Upper triangle of A contains elementary reflectors from CHETRD; = 'L': Lower triangle of A contains elementary reflectors from CHETRD.
TAU(i)
must contain the scalar factor of the elementary
reflector H(i), as returned by CHETRD.
WORK(1)
returns the optimal LWORK.
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.
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value