LAPACK  3.10.0
LAPACK: Linear Algebra PACKage

◆ srqt02()

subroutine srqt02 ( integer  M,
integer  N,
integer  K,
real, dimension( lda, * )  A,
real, dimension( lda, * )  AF,
real, dimension( lda, * )  Q,
real, dimension( lda, * )  R,
integer  LDA,
real, dimension( * )  TAU,
real, dimension( lwork )  WORK,
integer  LWORK,
real, dimension( * )  RWORK,
real, dimension( * )  RESULT 
)

SRQT02

Purpose:
 SRQT02 tests SORGRQ, which generates an m-by-n matrix Q with
 orthonornmal rows that is defined as the product of k elementary
 reflectors.

 Given the RQ factorization of an m-by-n matrix A, SRQT02 generates
 the orthogonal matrix Q defined by the factorization of the last k
 rows of A; it compares R(m-k+1:m,n-m+1:n) with
 A(m-k+1:m,1:n)*Q(n-m+1:n,1:n)', and checks that the rows of Q are
 orthonormal.
Parameters
[in]M
          M is INTEGER
          The number of rows of the matrix Q to be generated.  M >= 0.
[in]N
          N is INTEGER
          The number of columns of the matrix Q to be generated.
          N >= M >= 0.
[in]K
          K is INTEGER
          The number of elementary reflectors whose product defines the
          matrix Q. M >= K >= 0.
[in]A
          A is REAL array, dimension (LDA,N)
          The m-by-n matrix A which was factorized by SRQT01.
[in]AF
          AF is REAL array, dimension (LDA,N)
          Details of the RQ factorization of A, as returned by SGERQF.
          See SGERQF for further details.
[out]Q
          Q is REAL array, dimension (LDA,N)
[out]R
          R is REAL array, dimension (LDA,M)
[in]LDA
          LDA is INTEGER
          The leading dimension of the arrays A, AF, Q and L. LDA >= N.
[in]TAU
          TAU is REAL array, dimension (M)
          The scalar factors of the elementary reflectors corresponding
          to the RQ factorization in AF.
[out]WORK
          WORK is REAL array, dimension (LWORK)
[in]LWORK
          LWORK is INTEGER
          The dimension of the array WORK.
[out]RWORK
          RWORK is REAL array, dimension (M)
[out]RESULT
          RESULT is REAL array, dimension (2)
          The test ratios:
          RESULT(1) = norm( R - A*Q' ) / ( N * norm(A) * EPS )
          RESULT(2) = norm( I - Q*Q' ) / ( N * EPS )
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.

Definition at line 134 of file srqt02.f.

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, * ), Q( LDA, * ),
146  $ R( 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, sorgrq, 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 rows of the factorization to the array Q
191 *
192  CALL slaset( 'Full', m, n, rogue, rogue, q, lda )
193  IF( k.LT.n )
194  $ CALL slacpy( 'Full', k, n-k, af( m-k+1, 1 ), lda,
195  $ q( m-k+1, 1 ), lda )
196  IF( k.GT.1 )
197  $ CALL slacpy( 'Lower', k-1, k-1, af( m-k+2, n-k+1 ), lda,
198  $ q( m-k+2, n-k+1 ), lda )
199 *
200 * Generate the last n rows of the matrix Q
201 *
202  srnamt = 'SORGRQ'
203  CALL sorgrq( m, n, k, q, lda, tau( m-k+1 ), work, lwork, info )
204 *
205 * Copy R(m-k+1:m,n-m+1:n)
206 *
207  CALL slaset( 'Full', k, m, zero, zero, r( m-k+1, n-m+1 ), lda )
208  CALL slacpy( 'Upper', k, k, af( m-k+1, n-k+1 ), lda,
209  $ r( m-k+1, n-k+1 ), lda )
210 *
211 * Compute R(m-k+1:m,n-m+1:n) - A(m-k+1:m,1:n) * Q(n-m+1:n,1:n)'
212 *
213  CALL sgemm( 'No transpose', 'Transpose', k, m, n, -one,
214  $ a( m-k+1, 1 ), lda, q, lda, one, r( m-k+1, n-m+1 ),
215  $ lda )
216 *
217 * Compute norm( R - A*Q' ) / ( N * norm(A) * EPS ) .
218 *
219  anorm = slange( '1', k, n, a( m-k+1, 1 ), lda, rwork )
220  resid = slange( '1', k, m, r( m-k+1, n-m+1 ), lda, rwork )
221  IF( anorm.GT.zero ) THEN
222  result( 1 ) = ( ( resid / real( max( 1, n ) ) ) / anorm ) / eps
223  ELSE
224  result( 1 ) = zero
225  END IF
226 *
227 * Compute I - Q*Q'
228 *
229  CALL slaset( 'Full', m, m, zero, one, r, lda )
230  CALL ssyrk( 'Upper', 'No transpose', m, n, -one, q, lda, one, r,
231  $ lda )
232 *
233 * Compute norm( I - Q*Q' ) / ( N * EPS ) .
234 *
235  resid = slansy( '1', 'Upper', m, r, lda, rwork )
236 *
237  result( 2 ) = ( resid / real( max( 1, n ) ) ) / eps
238 *
239  RETURN
240 *
241 * End of SRQT02
242 *
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
real function slange(NORM, M, N, A, LDA, WORK)
SLANGE returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value ...
Definition: slange.f:114
subroutine sorgrq(M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
SORGRQ
Definition: sorgrq.f:128
real function slansy(NORM, UPLO, N, A, LDA, WORK)
SLANSY returns the value of the 1-norm, or the Frobenius norm, or the infinity norm,...
Definition: slansy.f:122
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
real function slamch(CMACH)
SLAMCH
Definition: slamch.f:68
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