LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
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◆ dopgtr()

subroutine dopgtr ( character uplo,
integer n,
double precision, dimension( * ) ap,
double precision, dimension( * ) tau,
double precision, dimension( ldq, * ) q,
integer ldq,
double precision, dimension( * ) work,
integer info )

DOPGTR

Download DOPGTR + dependencies [TGZ] [ZIP] [TXT]

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).
!>
Parameters
[in]UPLO
!>          UPLO is CHARACTER*1
!>          = 'U': Upper triangular packed storage used in previous
!>                 call to DSPTRD;
!>          = 'L': Lower triangular packed storage used in previous
!>                 call to DSPTRD.
!>
[in]N
!>          N is INTEGER
!>          The order of the matrix Q. N >= 0.
!>
[in]AP
!>          AP is DOUBLE PRECISION array, dimension (N*(N+1)/2)
!>          The vectors which define the elementary reflectors, as
!>          returned by DSPTRD.
!>
[in]TAU
!>          TAU is DOUBLE PRECISION array, dimension (N-1)
!>          TAU(i) must contain the scalar factor of the elementary
!>          reflector H(i), as returned by DSPTRD.
!>
[out]Q
!>          Q is DOUBLE PRECISION array, dimension (LDQ,N)
!>          The N-by-N orthogonal matrix Q.
!>
[in]LDQ
!>          LDQ is INTEGER
!>          The leading dimension of the array Q. LDQ >= max(1,N).
!>
[out]WORK
!>          WORK is DOUBLE PRECISION array, dimension (N-1)
!>
[out]INFO
!>          INFO is INTEGER
!>          = 0:  successful exit
!>          < 0:  if INFO = -i, the i-th argument had an illegal value
!>
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.