NAME

dopgtr - generate a real orthogonal matrix Q which is defined as the product of n-1 elementary reflectors H(i) of order n, as returned by DSPTRD using packed storage

SYNOPSIS

SUBROUTINE DOPGTR( UPLO, N, AP, TAU, Q, LDQ, WORK, INFO )

CHARACTER UPLO

INTEGER INFO, LDQ, N

DOUBLE PRECISION AP( ∗ ), Q( LDQ, ∗ ), TAU( ∗ ), WORK( ∗ )

#include <sunperf.h>

void dopgtr(char uplo, int n, double ∗dap, double ∗tau, double ∗q, int ldq, int ∗info) ;

PURPOSE

DOPGTR generates a real orthogonal matrix Q which is defined as the product of n-1 elementary reflectors H(i) of order n, as returned by DSPTRD using packed storage:
 
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) CHARACTER∗1
= ’U’: Upper triangular packed storage used in previous call to DSPTRD; = ’L’: Lower triangular packed storage used in previous call to DSPTRD.

N (input) INTEGER
The order of the matrix Q. N >= 0.

AP (input) DOUBLE PRECISION array, dimension (N∗(N+1)/2)
The vectors which define the elementary reflectors, as returned by DSPTRD.

TAU (input) DOUBLE PRECISION array, dimension (N-1)
TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by DSPTRD.

Q (output) DOUBLE PRECISION array, dimension (LDQ,N)
The N-by-N orthogonal matrix Q.

LDQ (input) INTEGER
The leading dimension of the array Q. LDQ >= max(1,N).

WORK (workspace) DOUBLE PRECISION array, dimension (N-1)

INFO (output) INTEGER
= 0:  successful exit
< 0:  if INFO = -i, the i-th argument had an illegal value

SunOS 5.0  —  Last change: 10 Dec 1998