LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
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◆ cla_gbrcond_c()

real function cla_gbrcond_c ( character  trans,
integer  n,
integer  kl,
integer  ku,
complex, dimension( ldab, * )  ab,
integer  ldab,
complex, dimension( ldafb, * )  afb,
integer  ldafb,
integer, dimension( * )  ipiv,
real, dimension( * )  c,
logical  capply,
integer  info,
complex, dimension( * )  work,
real, dimension( * )  rwork 
)

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

Download CLA_GBRCOND_C + dependencies [TGZ] [ZIP] [TXT]

Purpose:
    CLA_GBRCOND_C Computes the infinity norm condition number of
    op(A) * inv(diag(C)) where C is a REAL 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 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 array, dimension (LDAFB,N)
     Details of the LU factorization of the band matrix A, as
     computed by CGBTRF.  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 CGBTRF; row i of the matrix was interchanged
     with row IPIV(i).
[in]C
          C is REAL 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 array, dimension (2*N).
     Workspace.
[out]RWORK
          RWORK is REAL array, dimension (N).
     Workspace.
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.

Definition at line 158 of file cla_gbrcond_c.f.

161*
162* -- LAPACK computational 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 CHARACTER TRANS
168 LOGICAL CAPPLY
169 INTEGER N, KL, KU, KD, KE, LDAB, LDAFB, INFO
170* ..
171* .. Array Arguments ..
172 INTEGER IPIV( * )
173 COMPLEX AB( LDAB, * ), AFB( LDAFB, * ), WORK( * )
174 REAL C( * ), RWORK( * )
175* ..
176*
177* =====================================================================
178*
179* .. Local Scalars ..
180 LOGICAL NOTRANS
181 INTEGER KASE, I, J
182 REAL AINVNM, ANORM, TMP
183 COMPLEX ZDUM
184* ..
185* .. Local Arrays ..
186 INTEGER ISAVE( 3 )
187* ..
188* .. External Functions ..
189 LOGICAL LSAME
190 EXTERNAL lsame
191* ..
192* .. External Subroutines ..
193 EXTERNAL clacn2, cgbtrs, xerbla
194* ..
195* .. Intrinsic Functions ..
196 INTRINSIC abs, max
197* ..
198* .. Statement Functions ..
199 REAL CABS1
200* ..
201* .. Statement Function Definitions ..
202 cabs1( zdum ) = abs( real( zdum ) ) + abs( aimag( zdum ) )
203* ..
204* .. Executable Statements ..
205 cla_gbrcond_c = 0.0e+0
206*
207 info = 0
208 notrans = lsame( trans, 'N' )
209 IF ( .NOT. notrans .AND. .NOT. lsame( trans, 'T' ) .AND. .NOT.
210 $ lsame( trans, 'C' ) ) THEN
211 info = -1
212 ELSE IF( n.LT.0 ) THEN
213 info = -2
214 ELSE IF( kl.LT.0 .OR. kl.GT.n-1 ) THEN
215 info = -3
216 ELSE IF( ku.LT.0 .OR. ku.GT.n-1 ) THEN
217 info = -4
218 ELSE IF( ldab.LT.kl+ku+1 ) THEN
219 info = -6
220 ELSE IF( ldafb.LT.2*kl+ku+1 ) THEN
221 info = -8
222 END IF
223 IF( info.NE.0 ) THEN
224 CALL xerbla( 'CLA_GBRCOND_C', -info )
225 RETURN
226 END IF
227*
228* Compute norm of op(A)*op2(C).
229*
230 anorm = 0.0e+0
231 kd = ku + 1
232 ke = kl + 1
233 IF ( notrans ) THEN
234 DO i = 1, n
235 tmp = 0.0e+0
236 IF ( capply ) THEN
237 DO j = max( i-kl, 1 ), min( i+ku, n )
238 tmp = tmp + cabs1( ab( kd+i-j, j ) ) / c( j )
239 END DO
240 ELSE
241 DO j = max( i-kl, 1 ), min( i+ku, n )
242 tmp = tmp + cabs1( ab( kd+i-j, j ) )
243 END DO
244 END IF
245 rwork( i ) = tmp
246 anorm = max( anorm, tmp )
247 END DO
248 ELSE
249 DO i = 1, n
250 tmp = 0.0e+0
251 IF ( capply ) THEN
252 DO j = max( i-kl, 1 ), min( i+ku, n )
253 tmp = tmp + cabs1( ab( ke-i+j, i ) ) / c( j )
254 END DO
255 ELSE
256 DO j = max( i-kl, 1 ), min( i+ku, n )
257 tmp = tmp + cabs1( ab( ke-i+j, i ) )
258 END DO
259 END IF
260 rwork( i ) = tmp
261 anorm = max( anorm, tmp )
262 END DO
263 END IF
264*
265* Quick return if possible.
266*
267 IF( n.EQ.0 ) THEN
268 cla_gbrcond_c = 1.0e+0
269 RETURN
270 ELSE IF( anorm .EQ. 0.0e+0 ) THEN
271 RETURN
272 END IF
273*
274* Estimate the norm of inv(op(A)).
275*
276 ainvnm = 0.0e+0
277*
278 kase = 0
279 10 CONTINUE
280 CALL clacn2( n, work( n+1 ), work, ainvnm, kase, isave )
281 IF( kase.NE.0 ) THEN
282 IF( kase.EQ.2 ) THEN
283*
284* Multiply by R.
285*
286 DO i = 1, n
287 work( i ) = work( i ) * rwork( i )
288 END DO
289*
290 IF ( notrans ) THEN
291 CALL cgbtrs( 'No transpose', n, kl, ku, 1, afb, ldafb,
292 $ ipiv, work, n, info )
293 ELSE
294 CALL cgbtrs( 'Conjugate transpose', n, kl, ku, 1, afb,
295 $ ldafb, ipiv, work, n, info )
296 ENDIF
297*
298* Multiply by inv(C).
299*
300 IF ( capply ) THEN
301 DO i = 1, n
302 work( i ) = work( i ) * c( i )
303 END DO
304 END IF
305 ELSE
306*
307* Multiply by inv(C**H).
308*
309 IF ( capply ) THEN
310 DO i = 1, n
311 work( i ) = work( i ) * c( i )
312 END DO
313 END IF
314*
315 IF ( notrans ) THEN
316 CALL cgbtrs( 'Conjugate transpose', n, kl, ku, 1, afb,
317 $ ldafb, ipiv, work, n, info )
318 ELSE
319 CALL cgbtrs( 'No transpose', n, kl, ku, 1, afb, ldafb,
320 $ ipiv, work, n, info )
321 END IF
322*
323* Multiply by R.
324*
325 DO i = 1, n
326 work( i ) = work( i ) * rwork( i )
327 END DO
328 END IF
329 GO TO 10
330 END IF
331*
332* Compute the estimate of the reciprocal condition number.
333*
334 IF( ainvnm .NE. 0.0e+0 )
335 $ cla_gbrcond_c = 1.0e+0 / ainvnm
336*
337 RETURN
338*
339* End of CLA_GBRCOND_C
340*
xerbla
subroutine xerbla(srname, info)
Definition cblat2.f:3285
cgbtrs
subroutine cgbtrs(trans, n, kl, ku, nrhs, ab, ldab, ipiv, b, ldb, info)
CGBTRS
Definition cgbtrs.f:138
cla_gbrcond_c
real function cla_gbrcond_c(trans, n, kl, ku, ab, ldab, afb, ldafb, ipiv, c, capply, info, work, rwork)
CLA_GBRCOND_C computes the infinity norm condition number of op(A)*inv(diag(c)) for general banded ma...
Definition cla_gbrcond_c.f:161
clacn2
subroutine clacn2(n, v, x, est, kase, isave)
CLACN2 estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vec...
Definition clacn2.f:133
lsame
logical function lsame(ca, cb)
LSAME
Definition lsame.f:48
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