SUBROUTINE tdiagrw ( v, e, t, subd,n,nmax,nvmax )
USE Numeric_Kinds_Module
USE FileUnits_Module
IMPLICIT NONE
!==============================================================================
!     <tdiag>--calls tred3, tql2, and trbak3 to diagonalize a matrix
!     v(n*(n+1)/2) -- matrix to be diagonalized, must be symmetric
!     e(n) -- output, the eigenvalues of <v>
!     t(n,n) -- output, the eigenvectors of <v>
!     n  -- appropriate dimension variables   (INTEGER*4)
!     subd(n) -- scratch array used by tred2 and tql2
!==============================================================================
INTEGER  :: n, nmax, nvmax
INTEGER  :: nv, i, j, ierr
REAL(dp) :: e(nmax), t(nmax,nmax), subd(nmax), v(nvmax)

!==============================================================================
nv=(n*(n+1))/2

CALL tred3rw(n,nv,v,e,subd,subd,nmax,nvmax)

 DO i=1,n
   DO j=1,n
     t(j,i)=0.d0
   ENDDO
   t(i,i)=1.d0
 ENDDO

 CALL tql2rw(n,n,e,subd,t,ierr,nmax,nvmax)
 IF(ierr.ne.0)  WRITE(Output_Unit,10) ierr
 
 CALL trbak3rw(n,n,nv,v,n,t,nmax,nvmax)
 IF ( ierr .ne. 0 ) WRITE(Output_Unit,10) ierr

 10 FORMAT ( ' diagonalization error #', i3, ' returned by tql2' )

RETURN
!  --------------***END-tdiag***---------------------------------------
END