 LAPACK  3.10.0 LAPACK: Linear Algebra PACKage

◆ dget54()

 subroutine dget54 ( integer N, double precision, dimension( lda, * ) A, integer LDA, double precision, dimension( ldb, * ) B, integer LDB, double precision, dimension( lds, * ) S, integer LDS, double precision, dimension( ldt, * ) T, integer LDT, double precision, dimension( ldu, * ) U, integer LDU, double precision, dimension( ldv, * ) V, integer LDV, double precision, dimension( * ) WORK, double precision RESULT )

DGET54

Purpose:
DGET54 checks a generalized decomposition of the form

A = U*S*V'  and B = U*T* V'

where ' means transpose and U and V are orthogonal.

Specifically,

RESULT = ||( A - U*S*V', B - U*T*V' )|| / (||( A, B )||*n*ulp )
Parameters
 [in] N N is INTEGER The size of the matrix. If it is zero, DGET54 does nothing. It must be at least zero. [in] A A is DOUBLE PRECISION array, dimension (LDA, N) The original (unfactored) matrix A. [in] LDA LDA is INTEGER The leading dimension of A. It must be at least 1 and at least N. [in] B B is DOUBLE PRECISION array, dimension (LDB, N) The original (unfactored) matrix B. [in] LDB LDB is INTEGER The leading dimension of B. It must be at least 1 and at least N. [in] S S is DOUBLE PRECISION array, dimension (LDS, N) The factored matrix S. [in] LDS LDS is INTEGER The leading dimension of S. It must be at least 1 and at least N. [in] T T is DOUBLE PRECISION array, dimension (LDT, N) The factored matrix T. [in] LDT LDT is INTEGER The leading dimension of T. It must be at least 1 and at least N. [in] U U is DOUBLE PRECISION array, dimension (LDU, N) The orthogonal matrix on the left-hand side in the decomposition. [in] LDU LDU is INTEGER The leading dimension of U. LDU must be at least N and at least 1. [in] V V is DOUBLE PRECISION array, dimension (LDV, N) The orthogonal matrix on the left-hand side in the decomposition. [in] LDV LDV is INTEGER The leading dimension of V. LDV must be at least N and at least 1. [out] WORK WORK is DOUBLE PRECISION array, dimension (3*N**2) [out] RESULT RESULT is DOUBLE PRECISION The value RESULT, It is currently limited to 1/ulp, to avoid overflow. Errors are flagged by RESULT=10/ulp.

Definition at line 154 of file dget54.f.

156 *
157 * -- LAPACK test routine --
158 * -- LAPACK is a software package provided by Univ. of Tennessee, --
159 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
160 *
161 * .. Scalar Arguments ..
162  INTEGER LDA, LDB, LDS, LDT, LDU, LDV, N
163  DOUBLE PRECISION RESULT
164 * ..
165 * .. Array Arguments ..
166  DOUBLE PRECISION A( LDA, * ), B( LDB, * ), S( LDS, * ),
167  \$ T( LDT, * ), U( LDU, * ), V( LDV, * ),
168  \$ WORK( * )
169 * ..
170 *
171 * =====================================================================
172 *
173 * .. Parameters ..
174  DOUBLE PRECISION ZERO, ONE
175  parameter( zero = 0.0d+0, one = 1.0d+0 )
176 * ..
177 * .. Local Scalars ..
178  DOUBLE PRECISION ABNORM, ULP, UNFL, WNORM
179 * ..
180 * .. Local Arrays ..
181  DOUBLE PRECISION DUM( 1 )
182 * ..
183 * .. External Functions ..
184  DOUBLE PRECISION DLAMCH, DLANGE
185  EXTERNAL dlamch, dlange
186 * ..
187 * .. External Subroutines ..
188  EXTERNAL dgemm, dlacpy
189 * ..
190 * .. Intrinsic Functions ..
191  INTRINSIC dble, max, min
192 * ..
193 * .. Executable Statements ..
194 *
195  result = zero
196  IF( n.LE.0 )
197  \$ RETURN
198 *
199 * Constants
200 *
201  unfl = dlamch( 'Safe minimum' )
202  ulp = dlamch( 'Epsilon' )*dlamch( 'Base' )
203 *
204 * compute the norm of (A,B)
205 *
206  CALL dlacpy( 'Full', n, n, a, lda, work, n )
207  CALL dlacpy( 'Full', n, n, b, ldb, work( n*n+1 ), n )
208  abnorm = max( dlange( '1', n, 2*n, work, n, dum ), unfl )
209 *
210 * Compute W1 = A - U*S*V', and put in the array WORK(1:N*N)
211 *
212  CALL dlacpy( ' ', n, n, a, lda, work, n )
213  CALL dgemm( 'N', 'N', n, n, n, one, u, ldu, s, lds, zero,
214  \$ work( n*n+1 ), n )
215 *
216  CALL dgemm( 'N', 'C', n, n, n, -one, work( n*n+1 ), n, v, ldv,
217  \$ one, work, n )
218 *
219 * Compute W2 = B - U*T*V', and put in the workarray W(N*N+1:2*N*N)
220 *
221  CALL dlacpy( ' ', n, n, b, ldb, work( n*n+1 ), n )
222  CALL dgemm( 'N', 'N', n, n, n, one, u, ldu, t, ldt, zero,
223  \$ work( 2*n*n+1 ), n )
224 *
225  CALL dgemm( 'N', 'C', n, n, n, -one, work( 2*n*n+1 ), n, v, ldv,
226  \$ one, work( n*n+1 ), n )
227 *
228 * Compute norm(W)/ ( ulp*norm((A,B)) )
229 *
230  wnorm = dlange( '1', n, 2*n, work, n, dum )
231 *
232  IF( abnorm.GT.wnorm ) THEN
233  result = ( wnorm / abnorm ) / ( 2*n*ulp )
234  ELSE
235  IF( abnorm.LT.one ) THEN
236  result = ( min( wnorm, 2*n*abnorm ) / abnorm ) / ( 2*n*ulp )
237  ELSE
238  result = min( wnorm / abnorm, dble( 2*n ) ) / ( 2*n*ulp )
239  END IF
240  END IF
241 *
242  RETURN
243 *
244 * End of DGET54
245 *
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 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
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