DOPGTR
November 2006
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).
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 |