132 SUBROUTINE spbcon( UPLO, N, KD, AB, LDAB, ANORM, RCOND, WORK,
142 INTEGER INFO, KD, LDAB, N
147 REAL AB( ldab, * ), WORK( * )
154 parameter ( one = 1.0e+0, zero = 0.0e+0 )
160 REAL AINVNM, SCALE, SCALEL, SCALEU, SMLNUM
169 EXTERNAL lsame, isamax, slamch
182 upper = lsame( uplo,
'U' )
183 IF( .NOT.upper .AND. .NOT.lsame( uplo,
'L' ) )
THEN
185 ELSE IF( n.LT.0 )
THEN
187 ELSE IF( kd.LT.0 )
THEN
189 ELSE IF( ldab.LT.kd+1 )
THEN
191 ELSE IF( anorm.LT.zero )
THEN
195 CALL xerbla(
'SPBCON', -info )
205 ELSE IF( anorm.EQ.zero )
THEN
209 smlnum = slamch(
'Safe minimum' )
216 CALL slacn2( n, work( n+1 ), work, iwork, ainvnm, kase, isave )
222 CALL slatbs(
'Upper',
'Transpose',
'Non-unit', normin, n,
223 $ kd, ab, ldab, work, scalel, work( 2*n+1 ),
229 CALL slatbs(
'Upper',
'No transpose',
'Non-unit', normin, n,
230 $ kd, ab, ldab, work, scaleu, work( 2*n+1 ),
236 CALL slatbs(
'Lower',
'No transpose',
'Non-unit', normin, n,
237 $ kd, ab, ldab, work, scalel, work( 2*n+1 ),
243 CALL slatbs(
'Lower',
'Transpose',
'Non-unit', normin, n,
244 $ kd, ab, ldab, work, scaleu, work( 2*n+1 ),
250 scale = scalel*scaleu
251 IF( scale.NE.one )
THEN
252 ix = isamax( n, work, 1 )
253 IF( scale.LT.abs( work( ix ) )*smlnum .OR. scale.EQ.zero )
255 CALL srscl( n, scale, work, 1 )
263 $ rcond = ( one / ainvnm ) / anorm
subroutine srscl(N, SA, SX, INCX)
SRSCL multiplies a vector by the reciprocal of a real scalar.
subroutine spbcon(UPLO, N, KD, AB, LDAB, ANORM, RCOND, WORK, IWORK, INFO)
SPBCON
subroutine slatbs(UPLO, TRANS, DIAG, NORMIN, N, KD, AB, LDAB, X, SCALE, CNORM, INFO)
SLATBS solves a triangular banded system of equations.
subroutine xerbla(SRNAME, INFO)
XERBLA
subroutine slacn2(N, V, X, ISGN, EST, KASE, ISAVE)
SLACN2 estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vec...