LAPACK 3.11.0
LAPACK: Linear Algebra PACKage
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◆ cget52()

subroutine cget52 ( logical  LEFT,
integer  N,
complex, dimension( lda, * )  A,
integer  LDA,
complex, dimension( ldb, * )  B,
integer  LDB,
complex, dimension( lde, * )  E,
integer  LDE,
complex, dimension( * )  ALPHA,
complex, dimension( * )  BETA,
complex, dimension( * )  WORK,
real, dimension( * )  RWORK,
real, dimension( 2 )  RESULT 
)

CGET52

Purpose:
 CGET52  does an eigenvector check for the generalized eigenvalue
 problem.

 The basic test for right eigenvectors is:

                           | b(i) A E(i) -  a(i) B E(i) |
         RESULT(1) = max   -------------------------------
                      i    n ulp max( |b(i) A|, |a(i) B| )

 using the 1-norm.  Here, a(i)/b(i) = w is the i-th generalized
 eigenvalue of A - w B, or, equivalently, b(i)/a(i) = m is the i-th
 generalized eigenvalue of m A - B.

                         H   H  _      _
 For left eigenvectors, A , B , a, and b  are used.

 CGET52 also tests the normalization of E.  Each eigenvector is
 supposed to be normalized so that the maximum "absolute value"
 of its elements is 1, where in this case, "absolute value"
 of a complex value x is  |Re(x)| + |Im(x)| ; let us call this
 maximum "absolute value" norm of a vector v  M(v).
 if a(i)=b(i)=0, then the eigenvector is set to be the jth coordinate
 vector. The normalization test is:

         RESULT(2) =      max       | M(v(i)) - 1 | / ( n ulp )
                    eigenvectors v(i)
Parameters
[in]LEFT
          LEFT is LOGICAL
          =.TRUE.:  The eigenvectors in the columns of E are assumed
                    to be *left* eigenvectors.
          =.FALSE.: The eigenvectors in the columns of E are assumed
                    to be *right* eigenvectors.
[in]N
          N is INTEGER
          The size of the matrices.  If it is zero, CGET52 does
          nothing.  It must be at least zero.
[in]A
          A is COMPLEX array, dimension (LDA, N)
          The 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 COMPLEX array, dimension (LDB, N)
          The matrix B.
[in]LDB
          LDB is INTEGER
          The leading dimension of B.  It must be at least 1
          and at least N.
[in]E
          E is COMPLEX array, dimension (LDE, N)
          The matrix of eigenvectors.  It must be O( 1 ).
[in]LDE
          LDE is INTEGER
          The leading dimension of E.  It must be at least 1 and at
          least N.
[in]ALPHA
          ALPHA is COMPLEX array, dimension (N)
          The values a(i) as described above, which, along with b(i),
          define the generalized eigenvalues.
[in]BETA
          BETA is COMPLEX array, dimension (N)
          The values b(i) as described above, which, along with a(i),
          define the generalized eigenvalues.
[out]WORK
          WORK is COMPLEX array, dimension (N**2)
[out]RWORK
          RWORK is REAL array, dimension (N)
[out]RESULT
          RESULT is REAL array, dimension (2)
          The values computed by the test described above.  If A E or
          B E is likely to overflow, then RESULT(1:2) is set to
          10 / ulp.
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.

Definition at line 159 of file cget52.f.

161*
162* -- LAPACK test routine --
163* -- LAPACK is a software package provided by Univ. of Tennessee, --
164* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
165*
166* .. Scalar Arguments ..
167 LOGICAL LEFT
168 INTEGER LDA, LDB, LDE, N
169* ..
170* .. Array Arguments ..
171 REAL RESULT( 2 ), RWORK( * )
172 COMPLEX A( LDA, * ), ALPHA( * ), B( LDB, * ),
173 $ BETA( * ), E( LDE, * ), WORK( * )
174* ..
175*
176* =====================================================================
177*
178* .. Parameters ..
179 REAL ZERO, ONE
180 parameter( zero = 0.0e+0, one = 1.0e+0 )
181 COMPLEX CZERO, CONE
182 parameter( czero = ( 0.0e+0, 0.0e+0 ),
183 $ cone = ( 1.0e+0, 0.0e+0 ) )
184* ..
185* .. Local Scalars ..
186 CHARACTER NORMAB, TRANS
187 INTEGER J, JVEC
188 REAL ABMAX, ALFMAX, ANORM, BETMAX, BNORM, ENORM,
189 $ ENRMER, ERRNRM, SAFMAX, SAFMIN, SCALE, TEMP1,
190 $ ULP
191 COMPLEX ACOEFF, ALPHAI, BCOEFF, BETAI, X
192* ..
193* .. External Functions ..
194 REAL CLANGE, SLAMCH
195 EXTERNAL clange, slamch
196* ..
197* .. External Subroutines ..
198 EXTERNAL cgemv
199* ..
200* .. Intrinsic Functions ..
201 INTRINSIC abs, aimag, conjg, max, real
202* ..
203* .. Statement Functions ..
204 REAL ABS1
205* ..
206* .. Statement Function definitions ..
207 abs1( x ) = abs( real( x ) ) + abs( aimag( x ) )
208* ..
209* .. Executable Statements ..
210*
211 result( 1 ) = zero
212 result( 2 ) = zero
213 IF( n.LE.0 )
214 $ RETURN
215*
216 safmin = slamch( 'Safe minimum' )
217 safmax = one / safmin
218 ulp = slamch( 'Epsilon' )*slamch( 'Base' )
219*
220 IF( left ) THEN
221 trans = 'C'
222 normab = 'I'
223 ELSE
224 trans = 'N'
225 normab = 'O'
226 END IF
227*
228* Norm of A, B, and E:
229*
230 anorm = max( clange( normab, n, n, a, lda, rwork ), safmin )
231 bnorm = max( clange( normab, n, n, b, ldb, rwork ), safmin )
232 enorm = max( clange( 'O', n, n, e, lde, rwork ), ulp )
233 alfmax = safmax / max( one, bnorm )
234 betmax = safmax / max( one, anorm )
235*
236* Compute error matrix.
237* Column i = ( b(i) A - a(i) B ) E(i) / max( |a(i) B|, |b(i) A| )
238*
239 DO 10 jvec = 1, n
240 alphai = alpha( jvec )
241 betai = beta( jvec )
242 abmax = max( abs1( alphai ), abs1( betai ) )
243 IF( abs1( alphai ).GT.alfmax .OR. abs1( betai ).GT.betmax .OR.
244 $ abmax.LT.one ) THEN
245 scale = one / max( abmax, safmin )
246 alphai = scale*alphai
247 betai = scale*betai
248 END IF
249 scale = one / max( abs1( alphai )*bnorm, abs1( betai )*anorm,
250 $ safmin )
251 acoeff = scale*betai
252 bcoeff = scale*alphai
253 IF( left ) THEN
254 acoeff = conjg( acoeff )
255 bcoeff = conjg( bcoeff )
256 END IF
257 CALL cgemv( trans, n, n, acoeff, a, lda, e( 1, jvec ), 1,
258 $ czero, work( n*( jvec-1 )+1 ), 1 )
259 CALL cgemv( trans, n, n, -bcoeff, b, lda, e( 1, jvec ), 1,
260 $ cone, work( n*( jvec-1 )+1 ), 1 )
261 10 CONTINUE
262*
263 errnrm = clange( 'One', n, n, work, n, rwork ) / enorm
264*
265* Compute RESULT(1)
266*
267 result( 1 ) = errnrm / ulp
268*
269* Normalization of E:
270*
271 enrmer = zero
272 DO 30 jvec = 1, n
273 temp1 = zero
274 DO 20 j = 1, n
275 temp1 = max( temp1, abs1( e( j, jvec ) ) )
276 20 CONTINUE
277 enrmer = max( enrmer, abs( temp1-one ) )
278 30 CONTINUE
279*
280* Compute RESULT(2) : the normalization error in E.
281*
282 result( 2 ) = enrmer / ( real( n )*ulp )
283*
284 RETURN
285*
286* End of CGET52
287*
logical function lde(RI, RJ, LR)
Definition: dblat2.f:2970
subroutine cgemv(TRANS, M, N, ALPHA, A, LDA, X, INCX, BETA, Y, INCY)
CGEMV
Definition: cgemv.f:158
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
real function slamch(CMACH)
SLAMCH
Definition: slamch.f:68
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