LAPACK  3.10.0
LAPACK: Linear Algebra PACKage
sqlt02.f
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1 *> \brief \b SQLT02
2 *
3 * =========== DOCUMENTATION ===========
4 *
5 * Online html documentation available at
6 * http://www.netlib.org/lapack/explore-html/
7 *
8 * Definition:
9 * ===========
10 *
11 * SUBROUTINE SQLT02( M, N, K, A, AF, Q, L, LDA, TAU, WORK, LWORK,
12 * RWORK, RESULT )
13 *
14 * .. Scalar Arguments ..
15 * INTEGER K, LDA, LWORK, M, N
16 * ..
17 * .. Array Arguments ..
18 * REAL A( LDA, * ), AF( LDA, * ), L( LDA, * ),
19 * $ Q( LDA, * ), RESULT( * ), RWORK( * ), TAU( * ),
20 * $ WORK( LWORK )
21 * ..
22 *
23 *
24 *> \par Purpose:
25 * =============
26 *>
27 *> \verbatim
28 *>
29 *> SQLT02 tests SORGQL, which generates an m-by-n matrix Q with
30 *> orthonornmal columns that is defined as the product of k elementary
31 *> reflectors.
32 *>
33 *> Given the QL factorization of an m-by-n matrix A, SQLT02 generates
34 *> the orthogonal matrix Q defined by the factorization of the last k
35 *> columns of A; it compares L(m-n+1:m,n-k+1:n) with
36 *> Q(1:m,m-n+1:m)'*A(1:m,n-k+1:n), and checks that the columns of Q are
37 *> orthonormal.
38 *> \endverbatim
39 *
40 * Arguments:
41 * ==========
42 *
43 *> \param[in] M
44 *> \verbatim
45 *> M is INTEGER
46 *> The number of rows of the matrix Q to be generated. M >= 0.
47 *> \endverbatim
48 *>
49 *> \param[in] N
50 *> \verbatim
51 *> N is INTEGER
52 *> The number of columns of the matrix Q to be generated.
53 *> M >= N >= 0.
54 *> \endverbatim
55 *>
56 *> \param[in] K
57 *> \verbatim
58 *> K is INTEGER
59 *> The number of elementary reflectors whose product defines the
60 *> matrix Q. N >= K >= 0.
61 *> \endverbatim
62 *>
63 *> \param[in] A
64 *> \verbatim
65 *> A is REAL array, dimension (LDA,N)
66 *> The m-by-n matrix A which was factorized by SQLT01.
67 *> \endverbatim
68 *>
69 *> \param[in] AF
70 *> \verbatim
71 *> AF is REAL array, dimension (LDA,N)
72 *> Details of the QL factorization of A, as returned by SGEQLF.
73 *> See SGEQLF for further details.
74 *> \endverbatim
75 *>
76 *> \param[out] Q
77 *> \verbatim
78 *> Q is REAL array, dimension (LDA,N)
79 *> \endverbatim
80 *>
81 *> \param[out] L
82 *> \verbatim
83 *> L is REAL array, dimension (LDA,N)
84 *> \endverbatim
85 *>
86 *> \param[in] LDA
87 *> \verbatim
88 *> LDA is INTEGER
89 *> The leading dimension of the arrays A, AF, Q and L. LDA >= M.
90 *> \endverbatim
91 *>
92 *> \param[in] TAU
93 *> \verbatim
94 *> TAU is REAL array, dimension (N)
95 *> The scalar factors of the elementary reflectors corresponding
96 *> to the QL factorization in AF.
97 *> \endverbatim
98 *>
99 *> \param[out] WORK
100 *> \verbatim
101 *> WORK is REAL array, dimension (LWORK)
102 *> \endverbatim
103 *>
104 *> \param[in] LWORK
105 *> \verbatim
106 *> LWORK is INTEGER
107 *> The dimension of the array WORK.
108 *> \endverbatim
109 *>
110 *> \param[out] RWORK
111 *> \verbatim
112 *> RWORK is REAL array, dimension (M)
113 *> \endverbatim
114 *>
115 *> \param[out] RESULT
116 *> \verbatim
117 *> RESULT is REAL array, dimension (2)
118 *> The test ratios:
119 *> RESULT(1) = norm( L - Q'*A ) / ( M * norm(A) * EPS )
120 *> RESULT(2) = norm( I - Q'*Q ) / ( M * EPS )
121 *> \endverbatim
122 *
123 * Authors:
124 * ========
125 *
126 *> \author Univ. of Tennessee
127 *> \author Univ. of California Berkeley
128 *> \author Univ. of Colorado Denver
129 *> \author NAG Ltd.
130 *
131 *> \ingroup single_lin
132 *
133 * =====================================================================
134  SUBROUTINE sqlt02( M, N, K, A, AF, Q, L, LDA, TAU, WORK, LWORK,
135  $ RWORK, RESULT )
136 *
137 * -- LAPACK test routine --
138 * -- LAPACK is a software package provided by Univ. of Tennessee, --
139 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
140 *
141 * .. Scalar Arguments ..
142  INTEGER K, LDA, LWORK, M, N
143 * ..
144 * .. Array Arguments ..
145  REAL A( LDA, * ), AF( LDA, * ), L( LDA, * ),
146  $ q( lda, * ), result( * ), rwork( * ), tau( * ),
147  $ work( lwork )
148 * ..
149 *
150 * =====================================================================
151 *
152 * .. Parameters ..
153  REAL ZERO, ONE
154  parameter( zero = 0.0e+0, one = 1.0e+0 )
155  REAL ROGUE
156  parameter( rogue = -1.0e+10 )
157 * ..
158 * .. Local Scalars ..
159  INTEGER INFO
160  REAL ANORM, EPS, RESID
161 * ..
162 * .. External Functions ..
163  REAL SLAMCH, SLANGE, SLANSY
164  EXTERNAL slamch, slange, slansy
165 * ..
166 * .. External Subroutines ..
167  EXTERNAL sgemm, slacpy, slaset, sorgql, ssyrk
168 * ..
169 * .. Intrinsic Functions ..
170  INTRINSIC max, real
171 * ..
172 * .. Scalars in Common ..
173  CHARACTER*32 SRNAMT
174 * ..
175 * .. Common blocks ..
176  COMMON / srnamc / srnamt
177 * ..
178 * .. Executable Statements ..
179 *
180 * Quick return if possible
181 *
182  IF( m.EQ.0 .OR. n.EQ.0 .OR. k.EQ.0 ) THEN
183  result( 1 ) = zero
184  result( 2 ) = zero
185  RETURN
186  END IF
187 *
188  eps = slamch( 'Epsilon' )
189 *
190 * Copy the last k columns of the factorization to the array Q
191 *
192  CALL slaset( 'Full', m, n, rogue, rogue, q, lda )
193  IF( k.LT.m )
194  $ CALL slacpy( 'Full', m-k, k, af( 1, n-k+1 ), lda,
195  $ q( 1, n-k+1 ), lda )
196  IF( k.GT.1 )
197  $ CALL slacpy( 'Upper', k-1, k-1, af( m-k+1, n-k+2 ), lda,
198  $ q( m-k+1, n-k+2 ), lda )
199 *
200 * Generate the last n columns of the matrix Q
201 *
202  srnamt = 'SORGQL'
203  CALL sorgql( m, n, k, q, lda, tau( n-k+1 ), work, lwork, info )
204 *
205 * Copy L(m-n+1:m,n-k+1:n)
206 *
207  CALL slaset( 'Full', n, k, zero, zero, l( m-n+1, n-k+1 ), lda )
208  CALL slacpy( 'Lower', k, k, af( m-k+1, n-k+1 ), lda,
209  $ l( m-k+1, n-k+1 ), lda )
210 *
211 * Compute L(m-n+1:m,n-k+1:n) - Q(1:m,m-n+1:m)' * A(1:m,n-k+1:n)
212 *
213  CALL sgemm( 'Transpose', 'No transpose', n, k, m, -one, q, lda,
214  $ a( 1, n-k+1 ), lda, one, l( m-n+1, n-k+1 ), lda )
215 *
216 * Compute norm( L - Q'*A ) / ( M * norm(A) * EPS ) .
217 *
218  anorm = slange( '1', m, k, a( 1, n-k+1 ), lda, rwork )
219  resid = slange( '1', n, k, l( m-n+1, n-k+1 ), lda, rwork )
220  IF( anorm.GT.zero ) THEN
221  result( 1 ) = ( ( resid / real( max( 1, m ) ) ) / anorm ) / eps
222  ELSE
223  result( 1 ) = zero
224  END IF
225 *
226 * Compute I - Q'*Q
227 *
228  CALL slaset( 'Full', n, n, zero, one, l, lda )
229  CALL ssyrk( 'Upper', 'Transpose', n, m, -one, q, lda, one, l,
230  $ lda )
231 *
232 * Compute norm( I - Q'*Q ) / ( M * EPS ) .
233 *
234  resid = slansy( '1', 'Upper', n, l, lda, rwork )
235 *
236  result( 2 ) = ( resid / real( max( 1, m ) ) ) / eps
237 *
238  RETURN
239 *
240 * End of SQLT02
241 *
242  END
subroutine slaset(UPLO, M, N, ALPHA, BETA, A, LDA)
SLASET initializes the off-diagonal elements and the diagonal elements of a matrix to given values.
Definition: slaset.f:110
subroutine slacpy(UPLO, M, N, A, LDA, B, LDB)
SLACPY copies all or part of one two-dimensional array to another.
Definition: slacpy.f:103
subroutine sorgql(M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
SORGQL
Definition: sorgql.f:128
subroutine ssyrk(UPLO, TRANS, N, K, ALPHA, A, LDA, BETA, C, LDC)
SSYRK
Definition: ssyrk.f:169
subroutine sgemm(TRANSA, TRANSB, M, N, K, ALPHA, A, LDA, B, LDB, BETA, C, LDC)
SGEMM
Definition: sgemm.f:187
subroutine sqlt02(M, N, K, A, AF, Q, L, LDA, TAU, WORK, LWORK, RWORK, RESULT)
SQLT02
Definition: sqlt02.f:136