ssyev.f man page

ssyev.f —



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

Function/Subroutine Documentation

subroutine ssyev (characterJOBZ, characterUPLO, integerN, real, dimension( lda, * )A, integerLDA, real, dimension( * )W, real, dimension( * )WORK, integerLWORK, integerINFO)

SSYEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for SY matrices  


 SSYEV computes all eigenvalues and, optionally, eigenvectors of a
 real symmetric matrix A.


          JOBZ is CHARACTER*1
          = 'N':  Compute eigenvalues only;
          = 'V':  Compute eigenvalues and eigenvectors.


          UPLO is CHARACTER*1
          = 'U':  Upper triangle of A is stored;
          = 'L':  Lower triangle of A is stored.


          N is INTEGER
          The order of the matrix A.  N >= 0.


          A is REAL array, dimension (LDA, N)
          On entry, the symmetric matrix A.  If UPLO = 'U', the
          leading N-by-N upper triangular part of A contains the
          upper triangular part of the matrix A.  If UPLO = 'L',
          the leading N-by-N lower triangular part of A contains
          the lower triangular part of the matrix A.
          On exit, if JOBZ = 'V', then if INFO = 0, A contains the
          orthonormal eigenvectors of the matrix A.
          If JOBZ = 'N', then on exit the lower triangle (if UPLO='L')
          or the upper triangle (if UPLO='U') of A, including the
          diagonal, is destroyed.


          LDA is INTEGER
          The leading dimension of the array A.  LDA >= max(1,N).


          W is REAL array, dimension (N)
          If INFO = 0, the eigenvalues in ascending order.


          WORK is REAL array, dimension (MAX(1,LWORK))
          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.


          LWORK is INTEGER
          The length of the array WORK.  LWORK >= max(1,3*N-1).
          For optimal efficiency, LWORK >= (NB+2)*N,
          where NB is the blocksize for SSYTRD returned by ILAENV.

          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.


          INFO is INTEGER
          = 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 an intermediate tridiagonal
                form did not converge to zero.

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.


November 2011

Definition at line 133 of file ssyev.f.


Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

ssyev(3) is an alias of ssyev.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK