Move LAPACK trunk into position.

1 files changed, 180 insertions, 0 deletions

diff --git a/SRC/sstegr.f b/SRC/sstegr.f
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+      SUBROUTINE SSTEGR( JOBZ, RANGE, N, D, E, VL, VU, IL, IU,
+     $           ABSTOL, M, W, Z, LDZ, ISUPPZ, WORK, LWORK, IWORK,
+     $           LIWORK, INFO )
+
+      IMPLICIT NONE
+*
+*
+*  -- LAPACK computational routine (version 3.1) --
+*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
+*     November 2006
+*
+*     .. Scalar Arguments ..
+      CHARACTER          JOBZ, RANGE
+      INTEGER            IL, INFO, IU, LDZ, LIWORK, LWORK, M, N
+      REAL             ABSTOL, VL, VU
+*     ..
+*     .. Array Arguments ..
+      INTEGER            ISUPPZ( * ), IWORK( * )
+      REAL               D( * ), E( * ), W( * ), WORK( * )
+      REAL               Z( LDZ, * )
+*     ..
+*
+*  Purpose
+*  =======
+*
+*  SSTEGR computes selected eigenvalues and, optionally, eigenvectors
+*  of a real symmetric tridiagonal matrix T. Any such unreduced matrix has
+*  a well defined set of pairwise different real eigenvalues, the corresponding
+*  real eigenvectors are pairwise orthogonal.
+*
+*  The spectrum may be computed either completely or partially by specifying
+*  either an interval (VL,VU] or a range of indices IL:IU for the desired
+*  eigenvalues.
+*
+*  SSTEGR is a compatability wrapper around the improved SSTEMR routine.
+*  See SSTEMR for further details.
+*
+*  One important change is that the ABSTOL parameter no longer provides any
+*  benefit and hence is no longer used.
+*
+*  Note : SSTEGR and SSTEMR work only on machines which follow
+*  IEEE-754 floating-point standard in their handling of infinities and
+*  NaNs.  Normal execution may create these exceptiona values and hence
+*  may abort due to a floating point exception in environments which
+*  do not conform to the IEEE-754 standard.
+*
+*  Arguments
+*  =========
+*
+*  JOBZ    (input) CHARACTER*1
+*          = 'N':  Compute eigenvalues only;
+*          = 'V':  Compute eigenvalues and eigenvectors.
+*
+*  RANGE   (input) CHARACTER*1
+*          = 'A': all eigenvalues will be found.
+*          = 'V': all eigenvalues in the half-open interval (VL,VU]
+*                 will be found.
+*          = 'I': the IL-th through IU-th eigenvalues will be found.
+*
+*  N       (input) INTEGER
+*          The order of the matrix.  N >= 0.
+*
+*  D       (input/output) REAL array, dimension (N)
+*          On entry, the N diagonal elements of the tridiagonal matrix
+*          T. On exit, D is overwritten.
+*
+*  E       (input/output) REAL array, dimension (N)
+*          On entry, the (N-1) subdiagonal elements of the tridiagonal
+*          matrix T in elements 1 to N-1 of E. E(N) need not be set on
+*          input, but is used internally as workspace.
+*          On exit, E is overwritten.
+*
+*  VL      (input) REAL
+*  VU      (input) REAL
+*          If RANGE='V', the lower and upper bounds of the interval to
+*          be searched for eigenvalues. VL < VU.
+*          Not referenced if RANGE = 'A' or 'I'.
+*
+*  IL      (input) INTEGER
+*  IU      (input) INTEGER
+*          If RANGE='I', the indices (in ascending order) of the
+*          smallest and largest eigenvalues to be returned.
+*          1 <= IL <= IU <= N, if N > 0.
+*          Not referenced if RANGE = 'A' or 'V'.
+*
+*  ABSTOL  (input) REAL
+*          Unused.  Was the absolute error tolerance for the
+*          eigenvalues/eigenvectors in previous versions.
+*
+*  M       (output) INTEGER
+*          The total number of eigenvalues found.  0 <= M <= N.
+*          If RANGE = 'A', M = N, and if RANGE = 'I', M = IU-IL+1.
+*
+*  W       (output) REAL array, dimension (N)
+*          The first M elements contain the selected eigenvalues in
+*          ascending order.
+*
+*  Z       (output) REAL array, dimension (LDZ, max(1,M) )
+*          If JOBZ = 'V', and if INFO = 0, then the first M columns of Z
+*          contain the orthonormal eigenvectors of the matrix T
+*          corresponding to the selected eigenvalues, with the i-th
+*          column of Z holding the eigenvector associated with W(i).
+*          If JOBZ = 'N', then Z is not referenced.
+*          Note: the user must ensure that at least max(1,M) columns are
+*          supplied in the array Z; if RANGE = 'V', the exact value of M
+*          is not known in advance and an upper bound must be used.
+*          Supplying N columns is always safe.
+*
+*  LDZ     (input) INTEGER
+*          The leading dimension of the array Z.  LDZ >= 1, and if
+*          JOBZ = 'V', then LDZ >= max(1,N).
+*
+*  ISUPPZ  (output) INTEGER ARRAY, dimension ( 2*max(1,M) )
+*          The support of the eigenvectors in Z, i.e., the indices
+*          indicating the nonzero elements in Z. The i-th computed eigenvector
+*          is nonzero only in elements ISUPPZ( 2*i-1 ) through
+*          ISUPPZ( 2*i ). This is relevant in the case when the matrix
+*          is split. ISUPPZ is only accessed when JOBZ is 'V' and N > 0.
+*
+*  WORK    (workspace/output) REAL array, dimension (LWORK)
+*          On exit, if INFO = 0, WORK(1) returns the optimal
+*          (and minimal) LWORK.
+*
+*  LWORK   (input) INTEGER
+*          The dimension of the array WORK. LWORK >= max(1,18*N)
+*          if JOBZ = 'V', and LWORK >= max(1,12*N) if JOBZ = 'N'.
+*          If LWORK = -1, then a workspace query is assumed; the routine
+*          only calculates the optimal size of the WORK array, returns
+*          this value as the first entry of the WORK array, and no error
+*          message related to LWORK is issued by XERBLA.
+*
+*  IWORK   (workspace/output) INTEGER array, dimension (LIWORK)
+*          On exit, if INFO = 0, IWORK(1) returns the optimal LIWORK.
+*
+*  LIWORK  (input) INTEGER
+*          The dimension of the array IWORK.  LIWORK >= max(1,10*N)
+*          if the eigenvectors are desired, and LIWORK >= max(1,8*N)
+*          if only the eigenvalues are to be computed.
+*          If LIWORK = -1, then a workspace query is assumed; the
+*          routine only calculates the optimal size of the IWORK array,
+*          returns this value as the first entry of the IWORK array, and
+*          no error message related to LIWORK is issued by XERBLA.
+*
+*  INFO    (output) INTEGER
+*          On exit, INFO
+*          = 0:  successful exit
+*          < 0:  if INFO = -i, the i-th argument had an illegal value
+*          > 0:  if INFO = 1X, internal error in SLARRE,
+*                if INFO = 2X, internal error in SLARRV.
+*                Here, the digit X = ABS( IINFO ) < 10, where IINFO is
+*                the nonzero error code returned by SLARRE or
+*                SLARRV, respectively.
+*
+*  Further Details
+*  ===============
+*
+*  Based on contributions by
+*     Inderjit Dhillon, IBM Almaden, USA
+*     Osni Marques, LBNL/NERSC, USA
+*     Christof Voemel, LBNL/NERSC, USA
+*
+*  =====================================================================
+*
+*     .. Local Scalars ..
+      LOGICAL TRYRAC
+*     ..
+*     .. External Subroutines ..
+      EXTERNAL SSTEMR
+*     ..
+*     .. Executable Statements ..
+      INFO = 0
+      TRYRAC = .FALSE.
+
+      CALL SSTEMR( JOBZ, RANGE, N, D, E, VL, VU, IL, IU,
+     $                   M, W, Z, LDZ, N, ISUPPZ, TRYRAC, WORK, LWORK,
+     $                   IWORK, LIWORK, INFO )
+*
+*     End of SSTEGR
+*
+      END