dorgtr(3P) Sun Performance Library dorgtr(3P)NAMEdorgtr - generate a real orthogonal matrix Q which is defined as the
product of n-1 elementary reflectors of order N, as returned by DSYTRD
SYNOPSIS
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, double *tau,
long *info);
PURPOSEdorgtr generates a real orthogonal matrix Q which is defined as the
product of n-1 elementary reflectors of order N, as returned by DSYTRD:
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 DSYTRD; = 'L': Lower triangle of A contains elementary
reflectors from DSYTRD.
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 DSYTRD. 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 elementary
reflector H(i), as returned by DSYTRD.
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 opti‐
mal 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
6 Mar 2009 dorgtr(3P)
