210 $ WORK, LWORK, RWORK, INFO )
220 INTEGER INFO, KD, LDAB, LDZ, N, LWORK
223 REAL RWORK( * ), W( * )
224 COMPLEX AB( LDAB, * ), WORK( * ), Z( LDZ, * )
231 parameter( zero = 0.0e0, one = 1.0e0 )
234 LOGICAL LOWER, WANTZ, LQUERY
235 INTEGER IINFO, IMAX, INDE, INDWRK, INDRWK, ISCALE,
236 $ llwork, lwmin, lhtrd, lwtrd, ib, indhous
237 REAL ANRM, BIGNUM, EPS, RMAX, RMIN, SAFMIN, SIGMA,
243 REAL SLAMCH, CLANHB, SROUNDUP_LWORK
244 EXTERNAL lsame, slamch, clanhb, ilaenv2stage,
258 wantz = lsame( jobz,
'V' )
259 lower = lsame( uplo,
'L' )
260 lquery = ( lwork.EQ.-1 )
263 IF( .NOT.( lsame( jobz,
'N' ) ) )
THEN
265 ELSE IF( .NOT.( lower .OR. lsame( uplo,
'U' ) ) )
THEN
267 ELSE IF( n.LT.0 )
THEN
269 ELSE IF( kd.LT.0 )
THEN
271 ELSE IF( ldab.LT.kd+1 )
THEN
273 ELSE IF( ldz.LT.1 .OR. ( wantz .AND. ldz.LT.n ) )
THEN
280 work( 1 ) = sroundup_lwork(lwmin)
282 ib = ilaenv2stage( 2,
'CHETRD_HB2ST', jobz,
284 lhtrd = ilaenv2stage( 3,
'CHETRD_HB2ST', jobz,
286 lwtrd = ilaenv2stage( 4,
'CHETRD_HB2ST', jobz,
288 lwmin = lhtrd + lwtrd
289 work( 1 ) = sroundup_lwork(lwmin)
292 IF( lwork.LT.lwmin .AND. .NOT.lquery )
297 CALL xerbla(
'CHBEV_2STAGE ', -info )
299 ELSE IF( lquery )
THEN
310 w( 1 ) = real( ab( 1, 1 ) )
312 w( 1 ) = real( ab( kd+1, 1 ) )
321 safmin = slamch(
'Safe minimum' )
322 eps = slamch(
'Precision' )
323 smlnum = safmin / eps
324 bignum = one / smlnum
325 rmin = sqrt( smlnum )
326 rmax = sqrt( bignum )
330 anrm = clanhb(
'M', uplo, n, kd, ab, ldab, rwork )
332 IF( anrm.GT.zero .AND. anrm.LT.rmin )
THEN
335 ELSE IF( anrm.GT.rmax )
THEN
339 IF( iscale.EQ.1 )
THEN
341 CALL clascl(
'B', kd, kd, one, sigma, n, n, ab, ldab, info )
343 CALL clascl(
'Q', kd, kd, one, sigma, n, n, ab, ldab, info )
351 indwrk = indhous + lhtrd
352 llwork = lwork - indwrk + 1
355 $ rwork( inde ), work( indhous ), lhtrd,
356 $ work( indwrk ), llwork, iinfo )
360 IF( .NOT.wantz )
THEN
361 CALL ssterf( n, w, rwork( inde ), info )
364 CALL csteqr( jobz, n, w, rwork( inde ), z, ldz,
365 $ rwork( indrwk ), info )
370 IF( iscale.EQ.1 )
THEN
376 CALL sscal( imax, one / sigma, w, 1 )
381 work( 1 ) = sroundup_lwork(lwmin)
subroutine xerbla(srname, info)
subroutine chbev_2stage(jobz, uplo, n, kd, ab, ldab, w, z, ldz, work, lwork, rwork, info)
CHBEV_2STAGE computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER m...
subroutine chetrd_2stage(vect, uplo, n, a, lda, d, e, tau, hous2, lhous2, work, lwork, info)
CHETRD_2STAGE
subroutine chetrd_hb2st(stage1, vect, uplo, n, kd, ab, ldab, d, e, hous, lhous, work, lwork, info)
CHETRD_HB2ST reduces a complex Hermitian band matrix A to real symmetric tridiagonal form T
subroutine clascl(type, kl, ku, cfrom, cto, m, n, a, lda, info)
CLASCL multiplies a general rectangular matrix by a real scalar defined as cto/cfrom.
subroutine sscal(n, sa, sx, incx)
SSCAL
subroutine csteqr(compz, n, d, e, z, ldz, work, info)
CSTEQR
subroutine ssterf(n, d, e, info)
SSTERF