 LAPACK  3.10.1 LAPACK: Linear Algebra PACKage

## ◆ cget51()

 subroutine cget51 ( integer ITYPE, integer N, complex, dimension( lda, * ) A, integer LDA, complex, dimension( ldb, * ) B, integer LDB, complex, dimension( ldu, * ) U, integer LDU, complex, dimension( ldv, * ) V, integer LDV, complex, dimension( * ) WORK, real, dimension( * ) RWORK, real RESULT )

CGET51

Purpose:
```      CGET51  generally checks a decomposition of the form

A = U B V**H

where **H means conjugate transpose and U and V are unitary.

Specifically, if ITYPE=1

RESULT = | A - U B V**H | / ( |A| n ulp )

If ITYPE=2, then:

RESULT = | A - B | / ( |A| n ulp )

If ITYPE=3, then:

RESULT = | I - U U**H | / ( n ulp )```
Parameters
 [in] ITYPE ``` ITYPE is INTEGER Specifies the type of tests to be performed. =1: RESULT = | A - U B V**H | / ( |A| n ulp ) =2: RESULT = | A - B | / ( |A| n ulp ) =3: RESULT = | I - U U**H | / ( n ulp )``` [in] N ``` N is INTEGER The size of the matrix. If it is zero, CGET51 does nothing. It must be at least zero.``` [in] A ``` A is COMPLEX array, dimension (LDA, N) The original (unfactored) matrix.``` [in] LDA ``` LDA is INTEGER The leading dimension of A. It must be at least 1 and at least N.``` [in] B ``` B is COMPLEX array, dimension (LDB, N) The factored matrix.``` [in] LDB ``` LDB is INTEGER The leading dimension of B. It must be at least 1 and at least N.``` [in] U ``` U is COMPLEX array, dimension (LDU, N) The unitary matrix on the left-hand side in the decomposition. Not referenced if ITYPE=2``` [in] LDU ``` LDU is INTEGER The leading dimension of U. LDU must be at least N and at least 1.``` [in] V ``` V is COMPLEX array, dimension (LDV, N) The unitary matrix on the left-hand side in the decomposition. Not referenced if ITYPE=2``` [in] LDV ``` LDV is INTEGER The leading dimension of V. LDV must be at least N and at least 1.``` [out] WORK ` WORK is COMPLEX array, dimension (2*N**2)` [out] RWORK ` RWORK is REAL array, dimension (N)` [out] RESULT ``` RESULT is REAL The values computed by the test specified by ITYPE. The value is currently limited to 1/ulp, to avoid overflow. Errors are flagged by RESULT=10/ulp.```

Definition at line 153 of file cget51.f.

155 *
156 * -- LAPACK test routine --
157 * -- LAPACK is a software package provided by Univ. of Tennessee, --
158 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
159 *
160 * .. Scalar Arguments ..
161  INTEGER ITYPE, LDA, LDB, LDU, LDV, N
162  REAL RESULT
163 * ..
164 * .. Array Arguments ..
165  REAL RWORK( * )
166  COMPLEX A( LDA, * ), B( LDB, * ), U( LDU, * ),
167  \$ V( LDV, * ), WORK( * )
168 * ..
169 *
170 * =====================================================================
171 *
172 * .. Parameters ..
173  REAL ZERO, ONE, TEN
174  parameter( zero = 0.0e+0, one = 1.0e+0, ten = 10.0e+0 )
175  COMPLEX CZERO, CONE
176  parameter( czero = ( 0.0e+0, 0.0e+0 ),
177  \$ cone = ( 1.0e+0, 0.0e+0 ) )
178 * ..
179 * .. Local Scalars ..
180  INTEGER JCOL, JDIAG, JROW
181  REAL ANORM, ULP, UNFL, WNORM
182 * ..
183 * .. External Functions ..
184  REAL CLANGE, SLAMCH
185  EXTERNAL clange, slamch
186 * ..
187 * .. External Subroutines ..
188  EXTERNAL cgemm, clacpy
189 * ..
190 * .. Intrinsic Functions ..
191  INTRINSIC max, min, real
192 * ..
193 * .. Executable Statements ..
194 *
195  result = zero
196  IF( n.LE.0 )
197  \$ RETURN
198 *
199 * Constants
200 *
201  unfl = slamch( 'Safe minimum' )
202  ulp = slamch( 'Epsilon' )*slamch( 'Base' )
203 *
204 * Some Error Checks
205 *
206  IF( itype.LT.1 .OR. itype.GT.3 ) THEN
207  result = ten / ulp
208  RETURN
209  END IF
210 *
211  IF( itype.LE.2 ) THEN
212 *
213 * Tests scaled by the norm(A)
214 *
215  anorm = max( clange( '1', n, n, a, lda, rwork ), unfl )
216 *
217  IF( itype.EQ.1 ) THEN
218 *
219 * ITYPE=1: Compute W = A - U B V**H
220 *
221  CALL clacpy( ' ', n, n, a, lda, work, n )
222  CALL cgemm( 'N', 'N', n, n, n, cone, u, ldu, b, ldb, czero,
223  \$ work( n**2+1 ), n )
224 *
225  CALL cgemm( 'N', 'C', n, n, n, -cone, work( n**2+1 ), n, v,
226  \$ ldv, cone, work, n )
227 *
228  ELSE
229 *
230 * ITYPE=2: Compute W = A - B
231 *
232  CALL clacpy( ' ', n, n, b, ldb, work, n )
233 *
234  DO 20 jcol = 1, n
235  DO 10 jrow = 1, n
236  work( jrow+n*( jcol-1 ) ) = work( jrow+n*( jcol-1 ) )
237  \$ - a( jrow, jcol )
238  10 CONTINUE
239  20 CONTINUE
240  END IF
241 *
242 * Compute norm(W)/ ( ulp*norm(A) )
243 *
244  wnorm = clange( '1', n, n, work, n, rwork )
245 *
246  IF( anorm.GT.wnorm ) THEN
247  result = ( wnorm / anorm ) / ( n*ulp )
248  ELSE
249  IF( anorm.LT.one ) THEN
250  result = ( min( wnorm, n*anorm ) / anorm ) / ( n*ulp )
251  ELSE
252  result = min( wnorm / anorm, real( n ) ) / ( n*ulp )
253  END IF
254  END IF
255 *
256  ELSE
257 *
258 * Tests not scaled by norm(A)
259 *
260 * ITYPE=3: Compute U U**H - I
261 *
262  CALL cgemm( 'N', 'C', n, n, n, cone, u, ldu, u, ldu, czero,
263  \$ work, n )
264 *
265  DO 30 jdiag = 1, n
266  work( ( n+1 )*( jdiag-1 )+1 ) = work( ( n+1 )*( jdiag-1 )+
267  \$ 1 ) - cone
268  30 CONTINUE
269 *
270  result = min( clange( '1', n, n, work, n, rwork ),
271  \$ real( n ) ) / ( n*ulp )
272  END IF
273 *
274  RETURN
275 *
276 * End of CGET51
277 *
subroutine cgemm(TRANSA, TRANSB, M, N, K, ALPHA, A, LDA, B, LDB, BETA, C, LDC)
CGEMM
Definition: cgemm.f:187
real function clange(NORM, M, N, A, LDA, WORK)
CLANGE returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value ...
Definition: clange.f:115
subroutine clacpy(UPLO, M, N, A, LDA, B, LDB)
CLACPY copies all or part of one two-dimensional array to another.
Definition: clacpy.f:103
real function slamch(CMACH)
SLAMCH
Definition: slamch.f:68
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