FFT - SYMINV

SYNOPSIS
     
     CALL SYMINV( a , nd , n , cond , work , eps )
     
DESCRIPTION
     
     a    - array containing the lower triangle of matrix including
            the diagonal
            On output, a is overwritten by the inverse lower triangle
            matrice.
     
     nd   - integer first dimension of a
     
     n    - integer dimension of matrix a
     
     work - array of dimension n containing work space
     
     eps  - real optional parameter
            ill-conditioning test value (default is 0)
            eps>0 makes the positive definite test more severe.
            This optional parameter is not available on workstations.
     
     cond - estimated condition number
     
            if A is not positive-definite -
     
                 COND=-FLOAT(I)
     
            where I is the rank of the first principal minor of A that is
            not positive-definite.
     
            if A is positive definite     -
     
                 COND=1/(N*N*MAX(A(I,J))*MAX(AINVERTED(I,J)))
     
            i.e. in the infinity norm, an upper limit on the inverse of
     
                 NORM(A)*NORM(AINVERTED)
     
            cond  is small for ill-conditioned A.