1DOPGTR(1)                LAPACK routine (version 3.1)                DOPGTR(1)
2
3
4

NAME

6       DOPGTR  - a real orthogonal matrix Q which is defined as the product of
7       n-1 elementary reflectors H(i) of order n, as returned by DSPTRD  using
8       packed storage
9

SYNOPSIS

11       SUBROUTINE DOPGTR( UPLO, N, AP, TAU, Q, LDQ, WORK, INFO )
12
13           CHARACTER      UPLO
14
15           INTEGER        INFO, LDQ, N
16
17           DOUBLE         PRECISION AP( * ), Q( LDQ, * ), TAU( * ), WORK( * )
18

PURPOSE

20       DOPGTR  generates  a  real  orthogonal matrix Q which is defined as the
21       product of n-1 elementary reflectors H(i) of order n,  as  returned  by
22       DSPTRD using packed storage:
23
24       if UPLO = 'U', Q = H(n-1) . . . H(2) H(1),
25
26       if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).
27
28

ARGUMENTS

30       UPLO    (input) CHARACTER*1
31               = 'U': Upper triangular packed storage used in previous call to
32               DSPTRD; = 'L': Lower triangular packed storage used in previous
33               call to DSPTRD.
34
35       N       (input) INTEGER
36               The order of the matrix Q. N >= 0.
37
38       AP      (input) DOUBLE PRECISION array, dimension (N*(N+1)/2)
39               The vectors which define the elementary reflectors, as returned
40               by DSPTRD.
41
42       TAU     (input) DOUBLE PRECISION array, dimension (N-1)
43               TAU(i) must contain the scalar factor of the elementary reflec‐
44               tor H(i), as returned by DSPTRD.
45
46       Q       (output) DOUBLE PRECISION array, dimension (LDQ,N)
47               The N-by-N orthogonal matrix Q.
48
49       LDQ     (input) INTEGER
50               The leading dimension of the array Q. LDQ >= max(1,N).
51
52       WORK    (workspace) DOUBLE PRECISION array, dimension (N-1)
53
54       INFO    (output) INTEGER
55               = 0:  successful exit
56               < 0:  if INFO = -i, the i-th argument had an illegal value
57
58
59
60 LAPACK routine (version 3.1)    November 2006                       DOPGTR(1)
Impressum