1DSPEV(1)              LAPACK driver routine (version 3.1)             DSPEV(1)
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NAME

6       DSPEV  -  all  the  eigenvalues and, optionally, eigenvectors of a real
7       symmetric matrix A in packed storage
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SYNOPSIS

10       SUBROUTINE DSPEV( JOBZ, UPLO, N, AP, W, Z, LDZ, WORK, INFO )
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12           CHARACTER     JOBZ, UPLO
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14           INTEGER       INFO, LDZ, N
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16           DOUBLE        PRECISION AP( * ), W( * ), WORK( * ), Z( LDZ, * )
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PURPOSE

19       DSPEV computes all the eigenvalues and, optionally, eigenvectors  of  a
20       real symmetric matrix A in packed storage.
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ARGUMENTS

24       JOBZ    (input) CHARACTER*1
25               = 'N':  Compute eigenvalues only;
26               = 'V':  Compute eigenvalues and eigenvectors.
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28       UPLO    (input) CHARACTER*1
29               = 'U':  Upper triangle of A is stored;
30               = 'L':  Lower triangle of A is stored.
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32       N       (input) INTEGER
33               The order of the matrix A.  N >= 0.
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35       AP      (input/output) DOUBLE PRECISION array, dimension (N*(N+1)/2)
36               On  entry,  the upper or lower triangle of the symmetric matrix
37               A, packed columnwise in a linear array.  The j-th column  of  A
38               is  stored  in  the  array AP as follows: if UPLO = 'U', AP(i +
39               (j-1)*j/2) =  A(i,j)  for  1<=i<=j;  if  UPLO  =  'L',  AP(i  +
40               (j-1)*(2*n-j)/2) = A(i,j) for j<=i<=n.
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42               On  exit,  AP  is  overwritten  by  values generated during the
43               reduction to tridiagonal form.  If UPLO = 'U', the diagonal and
44               first  superdiagonal  of the tridiagonal matrix T overwrite the
45               corresponding elements of A, and if UPLO =  'L',  the  diagonal
46               and first subdiagonal of T overwrite the corresponding elements
47               of A.
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49       W       (output) DOUBLE PRECISION array, dimension (N)
50               If INFO = 0, the eigenvalues in ascending order.
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52       Z       (output) DOUBLE PRECISION array, dimension (LDZ, N)
53               If JOBZ = 'V', then if INFO = 0,  Z  contains  the  orthonormal
54               eigenvectors of the matrix A, with the i-th column of Z holding
55               the eigenvector associated with W(i).  If JOBZ = 'N', then Z is
56               not referenced.
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58       LDZ     (input) INTEGER
59               The  leading dimension of the array Z.  LDZ >= 1, and if JOBZ =
60               'V', LDZ >= max(1,N).
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62       WORK    (workspace) DOUBLE PRECISION array, dimension (3*N)
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64       INFO    (output) INTEGER
65               = 0:  successful exit.
66               < 0:  if INFO = -i, the i-th argument had an illegal value.
67               > 0:  if INFO = i, the algorithm failed  to  converge;  i  off-
68               diagonal  elements  of an intermediate tridiagonal form did not
69               converge to zero.
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73 LAPACK driver routine (version 3.N1o)vember 2006                        DSPEV(1)
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