DOPGTR(1) LAPACK routine (version 3.2) DOPGTR(1)NAME
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
SYNOPSIS
SUBROUTINE DOPGTR( UPLO, N, AP, TAU, Q, LDQ, WORK, INFO )
CHARACTER UPLO
INTEGER INFO, LDQ, N
DOUBLE PRECISION AP( * ), Q( LDQ, * ), TAU( * ), WORK( * )
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 reflec‐
tor 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
LAPACK routine (version 3.2) November 2008 DOPGTR(1)
