LAPACK  3.10.0 LAPACK: Linear Algebra PACKage

## ◆ zla_gbrcond_c()

 double precision function zla_gbrcond_c ( character TRANS, integer N, integer KL, integer KU, complex*16, dimension( ldab, * ) AB, integer LDAB, complex*16, dimension( ldafb, * ) AFB, integer LDAFB, integer, dimension( * ) IPIV, double precision, dimension( * ) C, logical CAPPLY, integer INFO, complex*16, dimension( * ) WORK, double precision, dimension( * ) RWORK )

ZLA_GBRCOND_C computes the infinity norm condition number of op(A)*inv(diag(c)) for general banded matrices.

Purpose:
```    ZLA_GBRCOND_C Computes the infinity norm condition number of
op(A) * inv(diag(C)) where C is a DOUBLE PRECISION vector.```
Parameters
 [in] TRANS ``` TRANS is CHARACTER*1 Specifies the form of the system of equations: = 'N': A * X = B (No transpose) = 'T': A**T * X = B (Transpose) = 'C': A**H * X = B (Conjugate Transpose = Transpose)``` [in] N ``` N is INTEGER The number of linear equations, i.e., the order of the matrix A. N >= 0.``` [in] KL ``` KL is INTEGER The number of subdiagonals within the band of A. KL >= 0.``` [in] KU ``` KU is INTEGER The number of superdiagonals within the band of A. KU >= 0.``` [in] AB ``` AB is COMPLEX*16 array, dimension (LDAB,N) On entry, the matrix A in band storage, in rows 1 to KL+KU+1. The j-th column of A is stored in the j-th column of the array AB as follows: AB(KU+1+i-j,j) = A(i,j) for max(1,j-KU)<=i<=min(N,j+kl)``` [in] LDAB ``` LDAB is INTEGER The leading dimension of the array AB. LDAB >= KL+KU+1.``` [in] AFB ``` AFB is COMPLEX*16 array, dimension (LDAFB,N) Details of the LU factorization of the band matrix A, as computed by ZGBTRF. U is stored as an upper triangular band matrix with KL+KU superdiagonals in rows 1 to KL+KU+1, and the multipliers used during the factorization are stored in rows KL+KU+2 to 2*KL+KU+1.``` [in] LDAFB ``` LDAFB is INTEGER The leading dimension of the array AFB. LDAFB >= 2*KL+KU+1.``` [in] IPIV ``` IPIV is INTEGER array, dimension (N) The pivot indices from the factorization A = P*L*U as computed by ZGBTRF; row i of the matrix was interchanged with row IPIV(i).``` [in] C ``` C is DOUBLE PRECISION array, dimension (N) The vector C in the formula op(A) * inv(diag(C)).``` [in] CAPPLY ``` CAPPLY is LOGICAL If .TRUE. then access the vector C in the formula above.``` [out] INFO ``` INFO is INTEGER = 0: Successful exit. i > 0: The ith argument is invalid.``` [out] WORK ``` WORK is COMPLEX*16 array, dimension (2*N). Workspace.``` [out] RWORK ``` RWORK is DOUBLE PRECISION array, dimension (N). Workspace.```

Definition at line 159 of file zla_gbrcond_c.f.

163 *
164 * -- LAPACK computational routine --
165 * -- LAPACK is a software package provided by Univ. of Tennessee, --
166 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
167 *
168 * .. Scalar Arguments ..
169  CHARACTER TRANS
170  LOGICAL CAPPLY
171  INTEGER N, KL, KU, KD, KE, LDAB, LDAFB, INFO
172 * ..
173 * .. Array Arguments ..
174  INTEGER IPIV( * )
175  COMPLEX*16 AB( LDAB, * ), AFB( LDAFB, * ), WORK( * )
176  DOUBLE PRECISION C( * ), RWORK( * )
177 *
178 *
179 * =====================================================================
180 *
181 * .. Local Scalars ..
182  LOGICAL NOTRANS
183  INTEGER KASE, I, J
184  DOUBLE PRECISION AINVNM, ANORM, TMP
185  COMPLEX*16 ZDUM
186 * ..
187 * .. Local Arrays ..
188  INTEGER ISAVE( 3 )
189 * ..
190 * .. External Functions ..
191  LOGICAL LSAME
192  EXTERNAL lsame
193 * ..
194 * .. External Subroutines ..
195  EXTERNAL zlacn2, zgbtrs, xerbla
196 * ..
197 * .. Intrinsic Functions ..
198  INTRINSIC abs, max
199 * ..
200 * .. Statement Functions ..
201  DOUBLE PRECISION CABS1
202 * ..
203 * .. Statement Function Definitions ..
204  cabs1( zdum ) = abs( dble( zdum ) ) + abs( dimag( zdum ) )
205 * ..
206 * .. Executable Statements ..
207  zla_gbrcond_c = 0.0d+0
208 *
209  info = 0
210  notrans = lsame( trans, 'N' )
211  IF ( .NOT. notrans .AND. .NOT. lsame( trans, 'T' ) .AND. .NOT.
212  \$ lsame( trans, 'C' ) ) THEN
213  info = -1
214  ELSE IF( n.LT.0 ) THEN
215  info = -2
216  ELSE IF( kl.LT.0 .OR. kl.GT.n-1 ) THEN
217  info = -3
218  ELSE IF( ku.LT.0 .OR. ku.GT.n-1 ) THEN
219  info = -4
220  ELSE IF( ldab.LT.kl+ku+1 ) THEN
221  info = -6
222  ELSE IF( ldafb.LT.2*kl+ku+1 ) THEN
223  info = -8
224  END IF
225  IF( info.NE.0 ) THEN
226  CALL xerbla( 'ZLA_GBRCOND_C', -info )
227  RETURN
228  END IF
229 *
230 * Compute norm of op(A)*op2(C).
231 *
232  anorm = 0.0d+0
233  kd = ku + 1
234  ke = kl + 1
235  IF ( notrans ) THEN
236  DO i = 1, n
237  tmp = 0.0d+0
238  IF ( capply ) THEN
239  DO j = max( i-kl, 1 ), min( i+ku, n )
240  tmp = tmp + cabs1( ab( kd+i-j, j ) ) / c( j )
241  END DO
242  ELSE
243  DO j = max( i-kl, 1 ), min( i+ku, n )
244  tmp = tmp + cabs1( ab( kd+i-j, j ) )
245  END DO
246  END IF
247  rwork( i ) = tmp
248  anorm = max( anorm, tmp )
249  END DO
250  ELSE
251  DO i = 1, n
252  tmp = 0.0d+0
253  IF ( capply ) THEN
254  DO j = max( i-kl, 1 ), min( i+ku, n )
255  tmp = tmp + cabs1( ab( ke-i+j, i ) ) / c( j )
256  END DO
257  ELSE
258  DO j = max( i-kl, 1 ), min( i+ku, n )
259  tmp = tmp + cabs1( ab( ke-i+j, i ) )
260  END DO
261  END IF
262  rwork( i ) = tmp
263  anorm = max( anorm, tmp )
264  END DO
265  END IF
266 *
267 * Quick return if possible.
268 *
269  IF( n.EQ.0 ) THEN
270  zla_gbrcond_c = 1.0d+0
271  RETURN
272  ELSE IF( anorm .EQ. 0.0d+0 ) THEN
273  RETURN
274  END IF
275 *
276 * Estimate the norm of inv(op(A)).
277 *
278  ainvnm = 0.0d+0
279 *
280  kase = 0
281  10 CONTINUE
282  CALL zlacn2( n, work( n+1 ), work, ainvnm, kase, isave )
283  IF( kase.NE.0 ) THEN
284  IF( kase.EQ.2 ) THEN
285 *
286 * Multiply by R.
287 *
288  DO i = 1, n
289  work( i ) = work( i ) * rwork( i )
290  END DO
291 *
292  IF ( notrans ) THEN
293  CALL zgbtrs( 'No transpose', n, kl, ku, 1, afb, ldafb,
294  \$ ipiv, work, n, info )
295  ELSE
296  CALL zgbtrs( 'Conjugate transpose', n, kl, ku, 1, afb,
297  \$ ldafb, ipiv, work, n, info )
298  ENDIF
299 *
300 * Multiply by inv(C).
301 *
302  IF ( capply ) THEN
303  DO i = 1, n
304  work( i ) = work( i ) * c( i )
305  END DO
306  END IF
307  ELSE
308 *
309 * Multiply by inv(C**H).
310 *
311  IF ( capply ) THEN
312  DO i = 1, n
313  work( i ) = work( i ) * c( i )
314  END DO
315  END IF
316 *
317  IF ( notrans ) THEN
318  CALL zgbtrs( 'Conjugate transpose', n, kl, ku, 1, afb,
319  \$ ldafb, ipiv, work, n, info )
320  ELSE
321  CALL zgbtrs( 'No transpose', n, kl, ku, 1, afb, ldafb,
322  \$ ipiv, work, n, info )
323  END IF
324 *
325 * Multiply by R.
326 *
327  DO i = 1, n
328  work( i ) = work( i ) * rwork( i )
329  END DO
330  END IF
331  GO TO 10
332  END IF
333 *
334 * Compute the estimate of the reciprocal condition number.
335 *
336  IF( ainvnm .NE. 0.0d+0 )
337  \$ zla_gbrcond_c = 1.0d+0 / ainvnm
338 *
339  RETURN
340 *
341 * End of ZLA_GBRCOND_C
342 *
subroutine xerbla(SRNAME, INFO)
XERBLA
Definition: xerbla.f:60
logical function lsame(CA, CB)
LSAME
Definition: lsame.f:53
double precision function zla_gbrcond_c(TRANS, N, KL, KU, AB, LDAB, AFB, LDAFB, IPIV, C, CAPPLY, INFO, WORK, RWORK)
ZLA_GBRCOND_C computes the infinity norm condition number of op(A)*inv(diag(c)) for general banded ma...
subroutine zgbtrs(TRANS, N, KL, KU, NRHS, AB, LDAB, IPIV, B, LDB, INFO)
ZGBTRS
Definition: zgbtrs.f:138
subroutine zlacn2(N, V, X, EST, KASE, ISAVE)
ZLACN2 estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vec...
Definition: zlacn2.f:133
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