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

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

10       SUBROUTINE SSBEV( JOBZ, UPLO, N, KD, AB, LDAB, W, Z, LDZ, WORK, INFO )
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12           CHARACTER     JOBZ, UPLO
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14           INTEGER       INFO, KD, LDAB, LDZ, N
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16           REAL          AB( LDAB, * ), W( * ), WORK( * ), Z( LDZ, * )
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PURPOSE

19       SSBEV computes all the eigenvalues and, optionally, eigenvectors  of  a
20       real symmetric band 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       KD      (input) INTEGER
35               The  number of superdiagonals of the matrix A if UPLO = 'U', or
36               the number of subdiagonals if UPLO = 'L'.  KD >= 0.
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38       AB      (input/output) REAL array, dimension (LDAB, N)
39               On entry, the upper or lower triangle  of  the  symmetric  band
40               matrix A, stored in the first KD+1 rows of the array.  The j-th
41               column of A is stored in the j-th column of  the  array  AB  as
42               follows:  if  UPLO  = 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-
43               kd)<=i<=j;  if  UPLO  =  'L',  AB(1+i-j,j)     =   A(i,j)   for
44               j<=i<=min(n,j+kd).  On exit, AB is overwritten by values gener‐
45               ated during the reduction to tridiagonal form.  If UPLO =  'U',
46               the  first  superdiagonal  and  the diagonal of the tridiagonal
47               matrix T are returned in rows KD and KD+1 of AB, and if UPLO  =
48               'L',  the  diagonal  and first subdiagonal of T are returned in
49               the first two rows of AB.
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51       LDAB    (input) INTEGER
52               The leading dimension of the array AB.  LDAB >= KD + 1.
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54       W       (output) REAL array, dimension (N)
55               If INFO = 0, the eigenvalues in ascending order.
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57       Z       (output) REAL array, dimension (LDZ, N)
58               If JOBZ = 'V', then if INFO = 0,  Z  contains  the  orthonormal
59               eigenvectors of the matrix A, with the i-th column of Z holding
60               the eigenvector associated with W(i).  If JOBZ = 'N', then Z is
61               not referenced.
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63       LDZ     (input) INTEGER
64               The  leading dimension of the array Z.  LDZ >= 1, and if JOBZ =
65               'V', LDZ >= max(1,N).
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67       WORK    (workspace) REAL array, dimension (max(1,3*N-2))
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69       INFO    (output) INTEGER
70               = 0:  successful exit
71               < 0:  if INFO = -i, the i-th argument had an illegal value
72               > 0:  if INFO = i, the algorithm failed  to  converge;  i  off-
73               diagonal  elements  of an intermediate tridiagonal form did not
74               converge to zero.
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78 LAPACK driver routine (version 3.N2o)vember 2008                        SSBEV(1)
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