sstevd (3p)

Name

sstevd - compute all eigenvalues and, optionally, eigenvectors of a real symmetric tridiagonal matrix

Synopsis

SUBROUTINE SSTEVD(JOBZ, N, D, E, Z, LDZ, WORK, LWORK, IWORK, LIWORK,
INFO)

CHARACTER*1 JOBZ
INTEGER N, LDZ, LWORK, LIWORK, INFO
INTEGER IWORK(*)
REAL D(*), E(*), Z(LDZ,*), WORK(*)

SUBROUTINE SSTEVD_64(JOBZ, N, D, E, Z, LDZ, WORK, LWORK, IWORK,
LIWORK, INFO)

CHARACTER*1 JOBZ
INTEGER*8 N, LDZ, LWORK, LIWORK, INFO
INTEGER*8 IWORK(*)
REAL D(*), E(*), Z(LDZ,*), WORK(*)




F95 INTERFACE
SUBROUTINE STEVD(JOBZ, N, D, E, Z, LDZ, WORK, LWORK, IWORK,
LIWORK, INFO)

CHARACTER(LEN=1) :: JOBZ
INTEGER :: N, LDZ, LWORK, LIWORK, INFO
INTEGER, DIMENSION(:) :: IWORK
REAL, DIMENSION(:) :: D, E, WORK
REAL, DIMENSION(:,:) :: Z

SUBROUTINE STEVD_64(JOBZ, N, D, E, Z, LDZ, WORK, LWORK, IWORK,
LIWORK, INFO)

CHARACTER(LEN=1) :: JOBZ
INTEGER(8) :: N, LDZ, LWORK, LIWORK, INFO
INTEGER(8), DIMENSION(:) :: IWORK
REAL, DIMENSION(:) :: D, E, WORK
REAL, DIMENSION(:,:) :: Z




C INTERFACE
#include <sunperf.h>

void sstevd(char jobz, int n, float *d, float *e, float  *z,  int  ldz,
int *info);

void  sstevd_64(char  jobz,  long n, float *d, float *e, float *z, long
ldz, long *info);

Description

Oracle Solaris Studio Performance Library                           sstevd(3P)



NAME
       sstevd  -  compute  all  eigenvalues and, optionally, eigenvectors of a
       real symmetric tridiagonal matrix


SYNOPSIS
       SUBROUTINE SSTEVD(JOBZ, N, D, E, Z, LDZ, WORK, LWORK, IWORK, LIWORK,
             INFO)

       CHARACTER*1 JOBZ
       INTEGER N, LDZ, LWORK, LIWORK, INFO
       INTEGER IWORK(*)
       REAL D(*), E(*), Z(LDZ,*), WORK(*)

       SUBROUTINE SSTEVD_64(JOBZ, N, D, E, Z, LDZ, WORK, LWORK, IWORK,
             LIWORK, INFO)

       CHARACTER*1 JOBZ
       INTEGER*8 N, LDZ, LWORK, LIWORK, INFO
       INTEGER*8 IWORK(*)
       REAL D(*), E(*), Z(LDZ,*), WORK(*)




   F95 INTERFACE
       SUBROUTINE STEVD(JOBZ, N, D, E, Z, LDZ, WORK, LWORK, IWORK,
              LIWORK, INFO)

       CHARACTER(LEN=1) :: JOBZ
       INTEGER :: N, LDZ, LWORK, LIWORK, INFO
       INTEGER, DIMENSION(:) :: IWORK
       REAL, DIMENSION(:) :: D, E, WORK
       REAL, DIMENSION(:,:) :: Z

       SUBROUTINE STEVD_64(JOBZ, N, D, E, Z, LDZ, WORK, LWORK, IWORK,
              LIWORK, INFO)

       CHARACTER(LEN=1) :: JOBZ
       INTEGER(8) :: N, LDZ, LWORK, LIWORK, INFO
       INTEGER(8), DIMENSION(:) :: IWORK
       REAL, DIMENSION(:) :: D, E, WORK
       REAL, DIMENSION(:,:) :: Z




   C INTERFACE
       #include <sunperf.h>

       void sstevd(char jobz, int n, float *d, float *e, float  *z,  int  ldz,
                 int *info);

       void  sstevd_64(char  jobz,  long n, float *d, float *e, float *z, long
                 ldz, long *info);



PURPOSE
       sstevd computes all eigenvalues and, optionally, eigenvectors of a real
       symmetric  tridiagonal  matrix.  If eigenvectors are desired, it uses a
       divide and conquer algorithm.

       The divide and conquer algorithm  makes  very  mild  assumptions  about
       floating  point arithmetic. It will work on machines with a guard digit
       in add/subtract, or on those binary machines without guard digits which
       subtract  like the Cray X-MP, Cray Y-MP, Cray C-90, or Cray-2. It could
       conceivably fail on hexadecimal or decimal machines without guard  dig-
       its, but we know of none.


ARGUMENTS
       JOBZ (input)
                 = 'N':  Compute eigenvalues only;
                 = 'V':  Compute eigenvalues and eigenvectors.


       N (input) The order of the matrix.  N >= 0.


       D (input/output)
                 On  entry,  the n diagonal elements of the tridiagonal matrix
                 A.  On exit, if INFO = 0, the eigenvalues in ascending order.


       E (input/output)
                 On  entry,  the (n-1) subdiagonal elements of the tridiagonal
                 matrix A, stored in elements 1 to N-1 of E; E(N) need not  be
                 set,  but is used by the routine.  On exit, the contents of E
                 are destroyed.


       Z (output)
                 If JOBZ = 'V', then if INFO = 0, Z contains  the  orthonormal
                 eigenvectors of the matrix A, with the i-th column of Z hold-
                 ing the eigenvector associated with D(i).   If  JOBZ  =  'N',
                 then Z is not referenced.


       LDZ (input)
                 The  leading dimension of the array Z.  LDZ >= 1, and if JOBZ
                 = 'V', LDZ >= max(1,N).


       WORK (workspace)
                 dimension (LWORK) On exit, if INFO = 0, WORK(1)  returns  the
                 optimal LWORK.


       LWORK (input)
                 The  dimension  of  the array WORK.  If JOBZ  = 'N' or N <= 1
                 then LWORK must be at least 1.  If JOBZ  = 'V' and N > 1 then
                 LWORK must be at least ( 1 + 4*N + N**2 ).

                 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)
                 On exit, if INFO = 0, IWORK(1) returns the optimal LIWORK.


       LIWORK (input)
                 The dimension of the array IWORK.  If JOBZ  = 'N' or N  <=  1
                 then  LIWORK  must  be  at least 1.  If JOBZ  = 'V' and N > 1
                 then LIWORK must be at least 3+5*N.

                 If LIWORK = -1, then a workspace query is assumed;  the  rou-
                 tine  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)
                 = 0:  successful exit
                 < 0:  if INFO = -i, the i-th argument had an illegal value
                 >  0:   if INFO = i, the algorithm failed to converge; i off-
                 diagonal elements of E did not converge to zero.




                                  7 Nov 2015                        sstevd(3P)