198 INTEGER INFO, LDA, LWORK, N
201 REAL RWORK( * ), W( * )
202 COMPLEX A( LDA, * ), WORK( * )
209 parameter( zero = 0.0e0, one = 1.0e0 )
211 parameter( cone = ( 1.0e0, 0.0e0 ) )
214 LOGICAL LOWER, LQUERY, WANTZ
215 INTEGER IINFO, IMAX, INDE, INDTAU, INDWRK, ISCALE,
216 $ llwork, lwmin, lhtrd, lwtrd, kd, ib, indhous
217 REAL ANRM, BIGNUM, EPS, RMAX, RMIN, SAFMIN, SIGMA,
224 EXTERNAL lsame, slamch, clanhe, ilaenv2stage
231 INTRINSIC real, max, sqrt
237 wantz = lsame( jobz,
'V' )
238 lower = lsame( uplo,
'L' )
239 lquery = ( lwork.EQ.-1 )
242 IF( .NOT.( lsame( jobz,
'N' ) ) )
THEN
244 ELSE IF( .NOT.( lower .OR. lsame( uplo,
'U' ) ) )
THEN
246 ELSE IF( n.LT.0 )
THEN
248 ELSE IF( lda.LT.max( 1, n ) )
THEN
253 kd = ilaenv2stage( 1,
'CHETRD_2STAGE', jobz, n, -1, -1, -1 )
254 ib = ilaenv2stage( 2,
'CHETRD_2STAGE', jobz, n, kd, -1, -1 )
255 lhtrd = ilaenv2stage( 3,
'CHETRD_2STAGE', jobz, n, kd, ib, -1 )
256 lwtrd = ilaenv2stage( 4,
'CHETRD_2STAGE', jobz, n, kd, ib, -1 )
257 lwmin = n + lhtrd + lwtrd
260 IF( lwork.LT.lwmin .AND. .NOT.lquery )
265 CALL xerbla(
'CHEEV_2STAGE ', -info )
267 ELSE IF( lquery )
THEN
278 w( 1 ) = real( a( 1, 1 ) )
287 safmin = slamch(
'Safe minimum' )
288 eps = slamch(
'Precision' )
289 smlnum = safmin / eps
290 bignum = one / smlnum
291 rmin = sqrt( smlnum )
292 rmax = sqrt( bignum )
296 anrm = clanhe(
'M', uplo, n, a, lda, rwork )
298 IF( anrm.GT.zero .AND. anrm.LT.rmin )
THEN
301 ELSE IF( anrm.GT.rmax )
THEN
306 $
CALL clascl( uplo, 0, 0, one, sigma, n, n, a, lda, info )
313 indwrk = indhous + lhtrd
314 llwork = lwork - indwrk + 1
317 $ work( indtau ), work( indhous ), lhtrd,
318 $ work( indwrk ), llwork, iinfo )
323 IF( .NOT.wantz )
THEN
324 CALL ssterf( n, w, rwork( inde ), info )
326 CALL cungtr( uplo, n, a, lda, work( indtau ), work( indwrk ),
329 CALL csteqr( jobz, n, w, rwork( inde ), a, lda,
330 $ rwork( indwrk ), info )
335 IF( iscale.EQ.1 )
THEN
341 CALL sscal( imax, one / sigma, w, 1 )
subroutine xerbla(SRNAME, INFO)
XERBLA
subroutine ssterf(N, D, E, INFO)
SSTERF
subroutine chetrd_2stage(VECT, UPLO, N, A, LDA, D, E, TAU, HOUS2, LHOUS2, WORK, LWORK, INFO)
CHETRD_2STAGE
subroutine cheev_2stage(JOBZ, UPLO, N, A, LDA, W, WORK, LWORK, RWORK, INFO)
CHEEV_2STAGE computes the eigenvalues and, optionally, the left and/or right eigenvectors for HE matr...
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 csteqr(COMPZ, N, D, E, Z, LDZ, WORK, INFO)
CSTEQR
subroutine cungtr(UPLO, N, A, LDA, TAU, WORK, LWORK, INFO)
CUNGTR
subroutine sscal(N, SA, SX, INCX)
SSCAL