LAPACK  3.10.1
LAPACK: Linear Algebra PACKage

◆ drqt01()

subroutine drqt01 ( integer  M,
integer  N,
double precision, dimension( lda, * )  A,
double precision, dimension( lda, * )  AF,
double precision, dimension( lda, * )  Q,
double precision, dimension( lda, * )  R,
integer  LDA,
double precision, dimension( * )  TAU,
double precision, dimension( lwork )  WORK,
integer  LWORK,
double precision, dimension( * )  RWORK,
double precision, dimension( * )  RESULT 
)

DRQT01

Purpose:
 DRQT01 tests DGERQF, which computes the RQ factorization of an m-by-n
 matrix A, and partially tests DORGRQ which forms the n-by-n
 orthogonal matrix Q.

 DRQT01 compares R with A*Q', and checks that Q is orthogonal.
Parameters
[in]M
          M is INTEGER
          The number of rows of the matrix A.  M >= 0.
[in]N
          N is INTEGER
          The number of columns of the matrix A.  N >= 0.
[in]A
          A is DOUBLE PRECISION array, dimension (LDA,N)
          The m-by-n matrix A.
[out]AF
          AF is DOUBLE PRECISION array, dimension (LDA,N)
          Details of the RQ factorization of A, as returned by DGERQF.
          See DGERQF for further details.
[out]Q
          Q is DOUBLE PRECISION array, dimension (LDA,N)
          The n-by-n orthogonal matrix Q.
[out]R
          R is DOUBLE PRECISION array, dimension (LDA,max(M,N))
[in]LDA
          LDA is INTEGER
          The leading dimension of the arrays A, AF, Q and L.
          LDA >= max(M,N).
[out]TAU
          TAU is DOUBLE PRECISION array, dimension (min(M,N))
          The scalar factors of the elementary reflectors, as returned
          by DGERQF.
[out]WORK
          WORK is DOUBLE PRECISION array, dimension (LWORK)
[in]LWORK
          LWORK is INTEGER
          The dimension of the array WORK.
[out]RWORK
          RWORK is DOUBLE PRECISION array, dimension (max(M,N))
[out]RESULT
          RESULT is DOUBLE PRECISION 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 124 of file drqt01.f.

126 *
127 * -- LAPACK test routine --
128 * -- LAPACK is a software package provided by Univ. of Tennessee, --
129 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
130 *
131 * .. Scalar Arguments ..
132  INTEGER LDA, LWORK, M, N
133 * ..
134 * .. Array Arguments ..
135  DOUBLE PRECISION A( LDA, * ), AF( LDA, * ), Q( LDA, * ),
136  $ R( LDA, * ), RESULT( * ), RWORK( * ), TAU( * ),
137  $ WORK( LWORK )
138 * ..
139 *
140 * =====================================================================
141 *
142 * .. Parameters ..
143  DOUBLE PRECISION ZERO, ONE
144  parameter( zero = 0.0d+0, one = 1.0d+0 )
145  DOUBLE PRECISION ROGUE
146  parameter( rogue = -1.0d+10 )
147 * ..
148 * .. Local Scalars ..
149  INTEGER INFO, MINMN
150  DOUBLE PRECISION ANORM, EPS, RESID
151 * ..
152 * .. External Functions ..
153  DOUBLE PRECISION DLAMCH, DLANGE, DLANSY
154  EXTERNAL dlamch, dlange, dlansy
155 * ..
156 * .. External Subroutines ..
157  EXTERNAL dgemm, dgerqf, dlacpy, dlaset, dorgrq, dsyrk
158 * ..
159 * .. Intrinsic Functions ..
160  INTRINSIC dble, max, min
161 * ..
162 * .. Scalars in Common ..
163  CHARACTER*32 SRNAMT
164 * ..
165 * .. Common blocks ..
166  COMMON / srnamc / srnamt
167 * ..
168 * .. Executable Statements ..
169 *
170  minmn = min( m, n )
171  eps = dlamch( 'Epsilon' )
172 *
173 * Copy the matrix A to the array AF.
174 *
175  CALL dlacpy( 'Full', m, n, a, lda, af, lda )
176 *
177 * Factorize the matrix A in the array AF.
178 *
179  srnamt = 'DGERQF'
180  CALL dgerqf( m, n, af, lda, tau, work, lwork, info )
181 *
182 * Copy details of Q
183 *
184  CALL dlaset( 'Full', n, n, rogue, rogue, q, lda )
185  IF( m.LE.n ) THEN
186  IF( m.GT.0 .AND. m.LT.n )
187  $ CALL dlacpy( 'Full', m, n-m, af, lda, q( n-m+1, 1 ), lda )
188  IF( m.GT.1 )
189  $ CALL dlacpy( 'Lower', m-1, m-1, af( 2, n-m+1 ), lda,
190  $ q( n-m+2, n-m+1 ), lda )
191  ELSE
192  IF( n.GT.1 )
193  $ CALL dlacpy( 'Lower', n-1, n-1, af( m-n+2, 1 ), lda,
194  $ q( 2, 1 ), lda )
195  END IF
196 *
197 * Generate the n-by-n matrix Q
198 *
199  srnamt = 'DORGRQ'
200  CALL dorgrq( n, n, minmn, q, lda, tau, work, lwork, info )
201 *
202 * Copy R
203 *
204  CALL dlaset( 'Full', m, n, zero, zero, r, lda )
205  IF( m.LE.n ) THEN
206  IF( m.GT.0 )
207  $ CALL dlacpy( 'Upper', m, m, af( 1, n-m+1 ), lda,
208  $ r( 1, n-m+1 ), lda )
209  ELSE
210  IF( m.GT.n .AND. n.GT.0 )
211  $ CALL dlacpy( 'Full', m-n, n, af, lda, r, lda )
212  IF( n.GT.0 )
213  $ CALL dlacpy( 'Upper', n, n, af( m-n+1, 1 ), lda,
214  $ r( m-n+1, 1 ), lda )
215  END IF
216 *
217 * Compute R - A*Q'
218 *
219  CALL dgemm( 'No transpose', 'Transpose', m, n, n, -one, a, lda, q,
220  $ lda, one, r, lda )
221 *
222 * Compute norm( R - Q'*A ) / ( N * norm(A) * EPS ) .
223 *
224  anorm = dlange( '1', m, n, a, lda, rwork )
225  resid = dlange( '1', m, n, r, lda, rwork )
226  IF( anorm.GT.zero ) THEN
227  result( 1 ) = ( ( resid / dble( max( 1, n ) ) ) / anorm ) / eps
228  ELSE
229  result( 1 ) = zero
230  END IF
231 *
232 * Compute I - Q*Q'
233 *
234  CALL dlaset( 'Full', n, n, zero, one, r, lda )
235  CALL dsyrk( 'Upper', 'No transpose', n, n, -one, q, lda, one, r,
236  $ lda )
237 *
238 * Compute norm( I - Q*Q' ) / ( N * EPS ) .
239 *
240  resid = dlansy( '1', 'Upper', n, r, lda, rwork )
241 *
242  result( 2 ) = ( resid / dble( max( 1, n ) ) ) / eps
243 *
244  RETURN
245 *
246 * End of DRQT01
247 *
double precision function dlamch(CMACH)
DLAMCH
Definition: dlamch.f:69
subroutine dlacpy(UPLO, M, N, A, LDA, B, LDB)
DLACPY copies all or part of one two-dimensional array to another.
Definition: dlacpy.f:103
subroutine dlaset(UPLO, M, N, ALPHA, BETA, A, LDA)
DLASET initializes the off-diagonal elements and the diagonal elements of a matrix to given values.
Definition: dlaset.f:110
subroutine dsyrk(UPLO, TRANS, N, K, ALPHA, A, LDA, BETA, C, LDC)
DSYRK
Definition: dsyrk.f:169
subroutine dgemm(TRANSA, TRANSB, M, N, K, ALPHA, A, LDA, B, LDB, BETA, C, LDC)
DGEMM
Definition: dgemm.f:187
double precision function dlange(NORM, M, N, A, LDA, WORK)
DLANGE returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value ...
Definition: dlange.f:114
subroutine dgerqf(M, N, A, LDA, TAU, WORK, LWORK, INFO)
DGERQF
Definition: dgerqf.f:139
subroutine dorgrq(M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
DORGRQ
Definition: dorgrq.f:128
double precision function dlansy(NORM, UPLO, N, A, LDA, WORK)
DLANSY returns the value of the 1-norm, or the Frobenius norm, or the infinity norm,...
Definition: dlansy.f:122
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