1SSYEV(1)              LAPACK driver routine (version 3.2)             SSYEV(1)
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NAME

6       SSYEV  -  computes  all  eigenvalues and, optionally, eigenvectors of a
7       real symmetric matrix A
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SYNOPSIS

10       SUBROUTINE SSYEV( JOBZ, UPLO, N, A, LDA, W, WORK, LWORK, INFO )
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12           CHARACTER     JOBZ, UPLO
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14           INTEGER       INFO, LDA, LWORK, N
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16           REAL          A( LDA, * ), W( * ), WORK( * )
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PURPOSE

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

23       JOBZ    (input) CHARACTER*1
24               = 'N':  Compute eigenvalues only;
25               = 'V':  Compute eigenvalues and eigenvectors.
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27       UPLO    (input) CHARACTER*1
28               = 'U':  Upper triangle of A is stored;
29               = 'L':  Lower triangle of A is stored.
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31       N       (input) INTEGER
32               The order of the matrix A.  N >= 0.
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34       A       (input/output) REAL array, dimension (LDA, N)
35               On  entry,  the symmetric matrix A.  If UPLO = 'U', the leading
36               N-by-N upper triangular part of A contains the upper triangular
37               part  of the matrix A.  If UPLO = 'L', the leading N-by-N lower
38               triangular part of A contains the lower triangular part of  the
39               matrix A.  On exit, if JOBZ = 'V', then if INFO = 0, A contains
40               the orthonormal eigenvectors of the matrix A.  If JOBZ  =  'N',
41               then on exit the lower triangle (if UPLO='L') or the upper tri‐
42               angle (if UPLO='U') of A, including the diagonal, is destroyed.
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44       LDA     (input) INTEGER
45               The leading dimension of the array A.  LDA >= max(1,N).
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47       W       (output) REAL array, dimension (N)
48               If INFO = 0, the eigenvalues in ascending order.
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50       WORK    (workspace/output) REAL array, dimension (MAX(1,LWORK))
51               On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
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53       LWORK   (input) INTEGER
54               The length of the array  WORK.   LWORK  >=  max(1,3*N-1).   For
55               optimal  efficiency,  LWORK >= (NB+2)*N, where NB is the block‐
56               size for SSYTRD returned by ILAENV.  If  LWORK  =  -1,  then  a
57               workspace  query  is  assumed;  the routine only calculates the
58               optimal size of the WORK array, returns this value as the first
59               entry  of the WORK array, and no error message related to LWORK
60               is issued by XERBLA.
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62       INFO    (output) INTEGER
63               = 0:  successful exit
64               < 0:  if INFO = -i, the i-th argument had an illegal value
65               > 0:  if INFO = i, the algorithm failed  to  converge;  i  off-
66               diagonal  elements  of an intermediate tridiagonal form did not
67               converge to zero.
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71 LAPACK driver routine (version 3.N2o)vember 2008                        SSYEV(1)
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