LAPACK  3.10.0
LAPACK: Linear Algebra PACKage

◆ zlqt02()

subroutine zlqt02 ( integer  M,
integer  N,
integer  K,
complex*16, dimension( lda, * )  A,
complex*16, dimension( lda, * )  AF,
complex*16, dimension( lda, * )  Q,
complex*16, dimension( lda, * )  L,
integer  LDA,
complex*16, dimension( * )  TAU,
complex*16, dimension( lwork )  WORK,
integer  LWORK,
double precision, dimension( * )  RWORK,
double precision, dimension( * )  RESULT 
)

ZLQT02

Purpose:
 ZLQT02 tests ZUNGLQ, which generates an m-by-n matrix Q with
 orthonornmal rows that is defined as the product of k elementary
 reflectors.

 Given the LQ factorization of an m-by-n matrix A, ZLQT02 generates
 the orthogonal matrix Q defined by the factorization of the first k
 rows of A; it compares L(1:k,1:m) with A(1:k,1:n)*Q(1:m,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 COMPLEX*16 array, dimension (LDA,N)
          The m-by-n matrix A which was factorized by ZLQT01.
[in]AF
          AF is COMPLEX*16 array, dimension (LDA,N)
          Details of the LQ factorization of A, as returned by ZGELQF.
          See ZGELQF for further details.
[out]Q
          Q is COMPLEX*16 array, dimension (LDA,N)
[out]L
          L is COMPLEX*16 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 COMPLEX*16 array, dimension (M)
          The scalar factors of the elementary reflectors corresponding
          to the LQ factorization in AF.
[out]WORK
          WORK is COMPLEX*16 array, dimension (LWORK)
[in]LWORK
          LWORK is INTEGER
          The dimension of the array WORK.
[out]RWORK
          RWORK is DOUBLE PRECISION array, dimension (M)
[out]RESULT
          RESULT is DOUBLE PRECISION 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 133 of file zlqt02.f.

135 *
136 * -- LAPACK test routine --
137 * -- LAPACK is a software package provided by Univ. of Tennessee, --
138 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
139 *
140 * .. Scalar Arguments ..
141  INTEGER K, LDA, LWORK, M, N
142 * ..
143 * .. Array Arguments ..
144  DOUBLE PRECISION RESULT( * ), RWORK( * )
145  COMPLEX*16 A( LDA, * ), AF( LDA, * ), L( LDA, * ),
146  $ Q( LDA, * ), TAU( * ), WORK( LWORK )
147 * ..
148 *
149 * =====================================================================
150 *
151 * .. Parameters ..
152  DOUBLE PRECISION ZERO, ONE
153  parameter( zero = 0.0d+0, one = 1.0d+0 )
154  COMPLEX*16 ROGUE
155  parameter( rogue = ( -1.0d+10, -1.0d+10 ) )
156 * ..
157 * .. Local Scalars ..
158  INTEGER INFO
159  DOUBLE PRECISION ANORM, EPS, RESID
160 * ..
161 * .. External Functions ..
162  DOUBLE PRECISION DLAMCH, ZLANGE, ZLANSY
163  EXTERNAL dlamch, zlange, zlansy
164 * ..
165 * .. External Subroutines ..
166  EXTERNAL zgemm, zherk, zlacpy, zlaset, zunglq
167 * ..
168 * .. Intrinsic Functions ..
169  INTRINSIC dble, dcmplx, max
170 * ..
171 * .. Scalars in Common ..
172  CHARACTER*32 SRNAMT
173 * ..
174 * .. Common blocks ..
175  COMMON / srnamc / srnamt
176 * ..
177 * .. Executable Statements ..
178 *
179  eps = dlamch( 'Epsilon' )
180 *
181 * Copy the first k rows of the factorization to the array Q
182 *
183  CALL zlaset( 'Full', m, n, rogue, rogue, q, lda )
184  CALL zlacpy( 'Upper', k, n-1, af( 1, 2 ), lda, q( 1, 2 ), lda )
185 *
186 * Generate the first n columns of the matrix Q
187 *
188  srnamt = 'ZUNGLQ'
189  CALL zunglq( m, n, k, q, lda, tau, work, lwork, info )
190 *
191 * Copy L(1:k,1:m)
192 *
193  CALL zlaset( 'Full', k, m, dcmplx( zero ), dcmplx( zero ), l,
194  $ lda )
195  CALL zlacpy( 'Lower', k, m, af, lda, l, lda )
196 *
197 * Compute L(1:k,1:m) - A(1:k,1:n) * Q(1:m,1:n)'
198 *
199  CALL zgemm( 'No transpose', 'Conjugate transpose', k, m, n,
200  $ dcmplx( -one ), a, lda, q, lda, dcmplx( one ), l,
201  $ lda )
202 *
203 * Compute norm( L - A*Q' ) / ( N * norm(A) * EPS ) .
204 *
205  anorm = zlange( '1', k, n, a, lda, rwork )
206  resid = zlange( '1', k, m, l, lda, rwork )
207  IF( anorm.GT.zero ) THEN
208  result( 1 ) = ( ( resid / dble( max( 1, n ) ) ) / anorm ) / eps
209  ELSE
210  result( 1 ) = zero
211  END IF
212 *
213 * Compute I - Q*Q'
214 *
215  CALL zlaset( 'Full', m, m, dcmplx( zero ), dcmplx( one ), l, lda )
216  CALL zherk( 'Upper', 'No transpose', m, n, -one, q, lda, one, l,
217  $ lda )
218 *
219 * Compute norm( I - Q*Q' ) / ( N * EPS ) .
220 *
221  resid = zlansy( '1', 'Upper', m, l, lda, rwork )
222 *
223  result( 2 ) = ( resid / dble( max( 1, n ) ) ) / eps
224 *
225  RETURN
226 *
227 * End of ZLQT02
228 *
double precision function dlamch(CMACH)
DLAMCH
Definition: dlamch.f:69
subroutine zgemm(TRANSA, TRANSB, M, N, K, ALPHA, A, LDA, B, LDB, BETA, C, LDC)
ZGEMM
Definition: zgemm.f:187
subroutine zherk(UPLO, TRANS, N, K, ALPHA, A, LDA, BETA, C, LDC)
ZHERK
Definition: zherk.f:173
double precision function zlange(NORM, M, N, A, LDA, WORK)
ZLANGE returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value ...
Definition: zlange.f:115
subroutine zlacpy(UPLO, M, N, A, LDA, B, LDB)
ZLACPY copies all or part of one two-dimensional array to another.
Definition: zlacpy.f:103
subroutine zlaset(UPLO, M, N, ALPHA, BETA, A, LDA)
ZLASET initializes the off-diagonal elements and the diagonal elements of a matrix to given values.
Definition: zlaset.f:106
subroutine zunglq(M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
ZUNGLQ
Definition: zunglq.f:127
double precision function zlansy(NORM, UPLO, N, A, LDA, WORK)
ZLANSY returns the value of the 1-norm, or the Frobenius norm, or the infinity norm,...
Definition: zlansy.f:123
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