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( * )
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 reflec
tors, as returned by DSPTRD.
TAU (input) DOUBLE PRECISION array, dimension (N-1)
TAU(i) must contain the scalar factor of the ele
mentary 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
gal value
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