dopgtr3lapack
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
Usage
- 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 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