133 SUBROUTINE ssyev( JOBZ, UPLO, N, A, LDA, W, WORK, LWORK, INFO )
142 INTEGER info, lda, lwork, n
145 REAL a( lda, * ), w( * ), work( * )
152 parameter( zero = 0.0e0, one = 1.0e0 )
155 LOGICAL lower, lquery, wantz
156 INTEGER iinfo, imax, inde, indtau, indwrk, iscale,
158 REAL anrm, bignum, eps, rmax, rmin, safmin, sigma,
178 wantz =
lsame( jobz,
'V' )
179 lower =
lsame( uplo,
'L' )
180 lquery = ( lwork.EQ.-1 )
183 IF( .NOT.( wantz .OR.
lsame( jobz,
'N' ) ) )
THEN
185 ELSE IF( .NOT.( lower .OR.
lsame( uplo,
'U' ) ) )
THEN
187 ELSE IF( n.LT.0 )
THEN
189 ELSE IF( lda.LT.max( 1, n ) )
THEN
194 nb =
ilaenv( 1,
'SSYTRD', uplo, n, -1, -1, -1 )
195 lwkopt = max( 1, ( nb+2 )*n )
198 IF( lwork.LT.max( 1, 3*n-1 ) .AND. .NOT.lquery )
203 CALL
xerbla(
'SSYEV ', -info )
205 ELSE IF( lquery )
THEN
225 safmin =
slamch(
'Safe minimum' )
226 eps =
slamch(
'Precision' )
227 smlnum = safmin / eps
228 bignum = one / smlnum
229 rmin = sqrt( smlnum )
230 rmax = sqrt( bignum )
234 anrm =
slansy(
'M', uplo, n, a, lda, work )
236 IF( anrm.GT.zero .AND. anrm.LT.rmin )
THEN
239 ELSE IF( anrm.GT.rmax )
THEN
244 $ CALL
slascl( uplo, 0, 0, one, sigma, n, n, a, lda, info )
251 llwork = lwork - indwrk + 1
252 CALL
ssytrd( uplo, n, a, lda, w, work( inde ), work( indtau ),
253 $ work( indwrk ), llwork, iinfo )
258 IF( .NOT.wantz )
THEN
259 CALL
ssterf( n, w, work( inde ), info )
261 CALL
sorgtr( uplo, n, a, lda, work( indtau ), work( indwrk ),
263 CALL
ssteqr( jobz, n, w, work( inde ), a, lda, work( indtau ),
269 IF( iscale.EQ.1 )
THEN
275 CALL
sscal( imax, one / sigma, w, 1 )
subroutine sorgtr(UPLO, N, A, LDA, TAU, WORK, LWORK, INFO)
SORGTR
subroutine xerbla(SRNAME, INFO)
XERBLA
logical function lsame(CA, CB)
LSAME
subroutine ssytrd(UPLO, N, A, LDA, D, E, TAU, WORK, LWORK, INFO)
SSYTRD
subroutine slascl(TYPE, KL, KU, CFROM, CTO, M, N, A, LDA, INFO)
SLASCL multiplies a general rectangular matrix by a real scalar defined as cto/cfrom.
real function slamch(CMACH)
SLAMCH
real function slansy(NORM, UPLO, N, A, LDA, WORK)
SLANSY returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a real symmetric matrix.
integer function ilaenv(ISPEC, NAME, OPTS, N1, N2, N3, N4)
subroutine ssyev(JOBZ, UPLO, N, A, LDA, W, WORK, LWORK, INFO)
SSYEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for SY matrices ...
subroutine ssterf(N, D, E, INFO)
SSTERF
subroutine ssteqr(COMPZ, N, D, E, Z, LDZ, WORK, INFO)
SSTEQR
subroutine sscal(N, SA, SX, INCX)
SSCAL