- SUBROUTINE DOPGTR(
- UPLO, N, AP, TAU, Q, LDQ, WORK, INFO )
- CHARACTER UPLO
- INTEGER INFO, LDQ, N
- DOUBLE PRECISION AP( * ), Q( LDQ, * ), TAU( * ), WORK( * )
PURPOSEDOPGTR 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).
- 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