LAPACK  3.10.0
LAPACK: Linear Algebra PACKage

◆ slqt01()

subroutine slqt01 ( integer  M,
integer  N,
real, dimension( lda, * )  A,
real, dimension( lda, * )  AF,
real, dimension( lda, * )  Q,
real, dimension( lda, * )  L,
integer  LDA,
real, dimension( * )  TAU,
real, dimension( lwork )  WORK,
integer  LWORK,
real, dimension( * )  RWORK,
real, dimension( * )  RESULT 
)

SLQT01

Purpose:
 SLQT01 tests SGELQF, which computes the LQ factorization of an m-by-n
 matrix A, and partially tests SORGLQ which forms the n-by-n
 orthogonal matrix Q.

 SLQT01 compares L 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 REAL array, dimension (LDA,N)
          The m-by-n matrix A.
[out]AF
          AF is REAL array, dimension (LDA,N)
          Details of the LQ factorization of A, as returned by SGELQF.
          See SGELQF for further details.
[out]Q
          Q is REAL array, dimension (LDA,N)
          The n-by-n orthogonal matrix Q.
[out]L
          L is REAL 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 REAL array, dimension (min(M,N))
          The scalar factors of the elementary reflectors, as returned
          by SGELQF.
[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 (max(M,N))
[out]RESULT
          RESULT is REAL array, dimension (2)
          The test ratios:
          RESULT(1) = norm( L - 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 slqt01.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  REAL A( LDA, * ), AF( LDA, * ), L( LDA, * ),
136  $ Q( LDA, * ), RESULT( * ), RWORK( * ), TAU( * ),
137  $ WORK( LWORK )
138 * ..
139 *
140 * =====================================================================
141 *
142 * .. Parameters ..
143  REAL ZERO, ONE
144  parameter( zero = 0.0e+0, one = 1.0e+0 )
145  REAL ROGUE
146  parameter( rogue = -1.0e+10 )
147 * ..
148 * .. Local Scalars ..
149  INTEGER INFO, MINMN
150  REAL ANORM, EPS, RESID
151 * ..
152 * .. External Functions ..
153  REAL SLAMCH, SLANGE, SLANSY
154  EXTERNAL slamch, slange, slansy
155 * ..
156 * .. External Subroutines ..
157  EXTERNAL sgelqf, sgemm, slacpy, slaset, sorglq, ssyrk
158 * ..
159 * .. Intrinsic Functions ..
160  INTRINSIC max, min, real
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 = slamch( 'Epsilon' )
172 *
173 * Copy the matrix A to the array AF.
174 *
175  CALL slacpy( 'Full', m, n, a, lda, af, lda )
176 *
177 * Factorize the matrix A in the array AF.
178 *
179  srnamt = 'SGELQF'
180  CALL sgelqf( m, n, af, lda, tau, work, lwork, info )
181 *
182 * Copy details of Q
183 *
184  CALL slaset( 'Full', n, n, rogue, rogue, q, lda )
185  IF( n.GT.1 )
186  $ CALL slacpy( 'Upper', m, n-1, af( 1, 2 ), lda, q( 1, 2 ), lda )
187 *
188 * Generate the n-by-n matrix Q
189 *
190  srnamt = 'SORGLQ'
191  CALL sorglq( n, n, minmn, q, lda, tau, work, lwork, info )
192 *
193 * Copy L
194 *
195  CALL slaset( 'Full', m, n, zero, zero, l, lda )
196  CALL slacpy( 'Lower', m, n, af, lda, l, lda )
197 *
198 * Compute L - A*Q'
199 *
200  CALL sgemm( 'No transpose', 'Transpose', m, n, n, -one, a, lda, q,
201  $ lda, one, l, lda )
202 *
203 * Compute norm( L - Q'*A ) / ( N * norm(A) * EPS ) .
204 *
205  anorm = slange( '1', m, n, a, lda, rwork )
206  resid = slange( '1', m, n, l, lda, rwork )
207  IF( anorm.GT.zero ) THEN
208  result( 1 ) = ( ( resid / real( max( 1, n ) ) ) / anorm ) / eps
209  ELSE
210  result( 1 ) = zero
211  END IF
212 *
213 * Compute I - Q*Q'
214 *
215  CALL slaset( 'Full', n, n, zero, one, l, lda )
216  CALL ssyrk( 'Upper', 'No transpose', n, n, -one, q, lda, one, l,
217  $ lda )
218 *
219 * Compute norm( I - Q*Q' ) / ( N * EPS ) .
220 *
221  resid = slansy( '1', 'Upper', n, l, lda, rwork )
222 *
223  result( 2 ) = ( resid / real( max( 1, n ) ) ) / eps
224 *
225  RETURN
226 *
227 * End of SLQT01
228 *
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 sgelqf(M, N, A, LDA, TAU, WORK, LWORK, INFO)
SGELQF
Definition: sgelqf.f:143
subroutine sorglq(M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
SORGLQ
Definition: sorglq.f:127
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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