Contents
dorgtr - generate a real orthogonal matrix Q which is
defined as the product of n-1 elementary reflectors of order
N, as returned by SSYTRD
SUBROUTINE DORGTR(UPLO, N, A, LDA, TAU, WORK, LWORK, INFO)
CHARACTER * 1 UPLO
INTEGER N, LDA, LWORK, INFO
DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*)
SUBROUTINE DORGTR_64(UPLO, N, A, LDA, TAU, WORK, LWORK, INFO)
CHARACTER * 1 UPLO
INTEGER*8 N, LDA, LWORK, INFO
DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*)
F95 INTERFACE
SUBROUTINE ORGTR(UPLO, [N], A, [LDA], TAU, [WORK], [LWORK], [INFO])
CHARACTER(LEN=1) :: UPLO
INTEGER :: N, LDA, LWORK, INFO
REAL(8), DIMENSION(:) :: TAU, WORK
REAL(8), DIMENSION(:,:) :: A
SUBROUTINE ORGTR_64(UPLO, [N], A, [LDA], TAU, [WORK], [LWORK], [INFO])
CHARACTER(LEN=1) :: UPLO
INTEGER(8) :: N, LDA, LWORK, INFO
REAL(8), DIMENSION(:) :: TAU, WORK
REAL(8), DIMENSION(:,:) :: A
C INTERFACE
#include <sunperf.h>
void dorgtr(char uplo, int n, double *a, int lda, double
*tau, int *info);
void dorgtr_64(char uplo, long n, double *a, long lda, dou-
ble *tau, long *info);
dorgtr generates a real orthogonal matrix Q which is defined
as the product of n-1 elementary reflectors of order N, as
returned by SSYTRD:
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 SSYTRD; = 'L': Lower triangle of A
contains elementary reflectors from SSYTRD.
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 SSYTRD. On exit, the
N-by-N orthogonal matrix Q.
LDA (input)
The leading dimension of the array A. LDA >=
max(1,N).
TAU (input)
TAU(i) must contain the scalar factor of the ele-
mentary reflector H(i), as returned by SSYTRD.
WORK (workspace)
On exit, if INFO = 0, WORK(1) returns the optimal
LWORK.
LWORK (input)
The dimension of the array WORK. LWORK >=
max(1,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
illegal value