TRBAK3(3F)

NAME
     TRBAK3, STRBAK3  -  EISPACK routine.  This subroutine forms the
     eigenvectors of a REAL SYMMETRIC matrix by back transforming those of the
     corresponding symmetric tridiagonal matrix determined by  TRED3.


SYNOPSYS
          subroutine  trbak3(nm, n, nv, a, m, z)
          integer          nm, n, nv, m
          double precision a(nv), z(nm,m)

          subroutine strbak3(nm, n, nv, a, m, z)
          integer          nm, n, nv, m
          real             a(nv), z(nm,m)



DESCRIPTION
     On Input

     NM must be set to the row dimension of two-dimensional array parameters
     as declared in the calling program dimension statement.

     N is the order of the matrix.

     NV must be set to the dimension of the array parameter A as declared in
     the calling program dimension statement.

     A contains information about the orthogonal transformations used in the
     reduction by  TRED3  in its first N*(N+1)/2 positions.

     M is the number of eigenvectors to be back transformed.

     Z contains the eigenvectors to be back transformed in its first M
     columns.  On Output

     Z contains the transformed eigenvectors in its first M columns.  Note
     that TRBAK3 preserves vector Euclidean norms.  Questions and comments
     should be directed to b. s. Garbow, APPLIED MATHEMATICS DIVISION, ARGONNE
     NATIONAL LABORATORY