1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
|
SUBROUTINE DTZRQF( M, N, A, LDA, TAU, INFO )
*
* -- LAPACK routine (version 3.2.2) --
* -- LAPACK is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* June 2010
*
* .. Scalar Arguments ..
INTEGER INFO, LDA, M, N
* ..
* .. Array Arguments ..
DOUBLE PRECISION A( LDA, * ), TAU( * )
* ..
*
* Purpose
* =======
*
* This routine is deprecated and has been replaced by routine DTZRZF.
*
* DTZRQF reduces the M-by-N ( M<=N ) real upper trapezoidal matrix A
* to upper triangular form by means of orthogonal transformations.
*
* The upper trapezoidal matrix A is factored as
*
* A = ( R 0 ) * Z,
*
* where Z is an N-by-N orthogonal matrix and R is an M-by-M upper
* triangular matrix.
*
* Arguments
* =========
*
* M (input) INTEGER
* The number of rows of the matrix A. M >= 0.
*
* N (input) INTEGER
* The number of columns of the matrix A. N >= M.
*
* A (input/output) DOUBLE PRECISION array, dimension (LDA,N)
* On entry, the leading M-by-N upper trapezoidal part of the
* array A must contain the matrix to be factorized.
* On exit, the leading M-by-M upper triangular part of A
* contains the upper triangular matrix R, and elements M+1 to
* N of the first M rows of A, with the array TAU, represent the
* orthogonal matrix Z as a product of M elementary reflectors.
*
* LDA (input) INTEGER
* The leading dimension of the array A. LDA >= max(1,M).
*
* TAU (output) DOUBLE PRECISION array, dimension (M)
* The scalar factors of the elementary reflectors.
*
* INFO (output) INTEGER
* = 0: successful exit
* < 0: if INFO = -i, the i-th argument had an illegal value
*
* Further Details
* ===============
*
* The factorization is obtained by Householder's method. The kth
* transformation matrix, Z( k ), which is used to introduce zeros into
* the ( m - k + 1 )th row of A, is given in the form
*
* Z( k ) = ( I 0 ),
* ( 0 T( k ) )
*
* where
*
* T( k ) = I - tau*u( k )*u( k )', u( k ) = ( 1 ),
* ( 0 )
* ( z( k ) )
*
* tau is a scalar and z( k ) is an ( n - m ) element vector.
* tau and z( k ) are chosen to annihilate the elements of the kth row
* of X.
*
* The scalar tau is returned in the kth element of TAU and the vector
* u( k ) in the kth row of A, such that the elements of z( k ) are
* in a( k, m + 1 ), ..., a( k, n ). The elements of R are returned in
* the upper triangular part of A.
*
* Z is given by
*
* Z = Z( 1 ) * Z( 2 ) * ... * Z( m ).
*
* =====================================================================
*
* .. Parameters ..
DOUBLE PRECISION ONE, ZERO
PARAMETER ( ONE = 1.0D+0, ZERO = 0.0D+0 )
* ..
* .. Local Scalars ..
INTEGER I, K, M1
* ..
* .. Intrinsic Functions ..
INTRINSIC MAX, MIN
* ..
* .. External Subroutines ..
EXTERNAL DAXPY, DCOPY, DGEMV, DGER, DLARFG, XERBLA
* ..
* .. Executable Statements ..
*
* Test the input parameters.
*
INFO = 0
IF( M.LT.0 ) THEN
INFO = -1
ELSE IF( N.LT.M ) THEN
INFO = -2
ELSE IF( LDA.LT.MAX( 1, M ) ) THEN
INFO = -4
END IF
IF( INFO.NE.0 ) THEN
CALL XERBLA( 'DTZRQF', -INFO )
RETURN
END IF
*
* Perform the factorization.
*
IF( M.EQ.0 )
$ RETURN
IF( M.EQ.N ) THEN
DO 10 I = 1, N
TAU( I ) = ZERO
10 CONTINUE
ELSE
M1 = MIN( M+1, N )
DO 20 K = M, 1, -1
*
* Use a Householder reflection to zero the kth row of A.
* First set up the reflection.
*
CALL DLARFG( N-M+1, A( K, K ), A( K, M1 ), LDA, TAU( K ) )
*
IF( ( TAU( K ).NE.ZERO ) .AND. ( K.GT.1 ) ) THEN
*
* We now perform the operation A := A*P( k ).
*
* Use the first ( k - 1 ) elements of TAU to store a( k ),
* where a( k ) consists of the first ( k - 1 ) elements of
* the kth column of A. Also let B denote the first
* ( k - 1 ) rows of the last ( n - m ) columns of A.
*
CALL DCOPY( K-1, A( 1, K ), 1, TAU, 1 )
*
* Form w = a( k ) + B*z( k ) in TAU.
*
CALL DGEMV( 'No transpose', K-1, N-M, ONE, A( 1, M1 ),
$ LDA, A( K, M1 ), LDA, ONE, TAU, 1 )
*
* Now form a( k ) := a( k ) - tau*w
* and B := B - tau*w*z( k )'.
*
CALL DAXPY( K-1, -TAU( K ), TAU, 1, A( 1, K ), 1 )
CALL DGER( K-1, N-M, -TAU( K ), TAU, 1, A( K, M1 ), LDA,
$ A( 1, M1 ), LDA )
END IF
20 CONTINUE
END IF
*
RETURN
*
* End of DTZRQF
*
END
|
