subroutine lsupdxx(
     &     nn, ifail, lphprint
     &     , jmin, jmax, nupdate
     &     , ff, fmin, fold, gnorm0, dotdg
     &     , gg, dd, xx, xdiff
     &     , tmin, tmax, tact, epsx
     &     )

c     ==================================================================
c     SUBROUTINE lsupdxx
c     ==================================================================
c
c     o conceived for variable online/offline version
c       computes - new descent direction dd based on latest 
c                  available gradient
c                - new tact based on new dd
c                - new control vector xx needed for offline run
c
c     o started: Patrick Heimbach, MIT/EAPS
c                29-Feb-2000: 
c
c     o Version 2.1.0, 02-Mar-2000: Patrick Heimbach, MIT/EAPS
c
c     ==================================================================
c     SUBROUTINE lsupdxx
c     ==================================================================
c

#include "blas1.h"
      implicit none
      include 'mpif.h'

c-----------------------------------------
c declare arguments
c-----------------------------------------
      integer nmax
      parameter( nmax = MAX_INDEPEND )
      integer nn, jmin, jmax, nupdate, ifail
      double precision    ff, fmin, fold, gnorm0, dotdg,dnorm
      double precision    gg(nn), dd(nn), xx(nn), xdiff(nn)
      double precision    tmin, tmax, tact, epsx,temp
      logical lphprint

      integer pidlen,myindx(2)
      integer status(MPI_STATUS_SIZE),ierr
      integer myid, nprocs,mystart,myend
      common /mpi_parm/ myid,nprocs,mystart,myend

c-----------------------------------------
C declare local variables
c-----------------------------------------
      integer i
      double precision    fdiff, preco

      real*8,allocatable:: vv(:)
      integer, allocatable:: displs(:)
      integer, allocatable:: counts(:) 
      double precision     DDOT,DNRM2
      external DDOT,DNRM2

c     ==================================================================

c-----------------------------------------
c use Fletchers scaling
c and initialize diagional to 1.
c-----------------------------------------
c
      if ( ( jmax .eq. 0 ) .or. (nupdate .eq. 0 ) ) then

         if (jmax .eq. 0) then
            fold = fmin
!            if (lphprint .and. myid .eq. 0) 
!     &           print *, 'pathei-lsopt: using fold = fmin = ', fmin
         end if
!         fdiff = fold - ff
         fdiff = .01D0*ff
         if (jmax .eq. 0) fdiff = ABS(fdiff)
         
         preco = 2. * fdiff / (gnorm0*gnorm0)
         do i = 1, nn
            dd(i)    = -gg(i)*preco
         end do

         if (lphprint .and. myid .eq. 0) 
     &        print *, 'pathei-lsopt: first estimate of dd via ',
     &        '.01*ff'

c-----------------------------------------
c use the matrix stored in [diag]
c and the (y,s) pairs
c-----------------------------------------

      else

            do i = 1, nn
               dd(i) = -gg(i)
            end do

            if (jmax .gt. 0) then
               call hessupd( nn, nupdate, dd, jmin, jmax, xdiff, 
     &              lphprint )
            else
               if (lphprint .and. myid .eq. 0) 
     &              print *, 'pathei-lsopt: no hessupd for first optim.'
            end if

      endif

c-----------------------------------------
c check whether new direction is a descent one
c-----------------------------------------

         temp  = DDOT( nn, dd, 1, gg, 1 )
         call MPI_ALLREDUCE(temp,dotdg,1,MPI_DOUBLE_PRECISION,MPI_SUM,MPI_COMM_WORLD,ierr)
         
         if (dotdg .ge. 0.0) then
            ifail = 4
            if(myid .eq. 0) print *,'bnc: ifail = 4, dotdg > 0.'
            goto 999
         end if

c----------------------------------
c declare arguments
c----------------------------------

      tmin = 0.
      do i = 1, nn
         tmin = max( tmin, abs(dd(i)) )
      end do
      temp = tmin
      call MPI_ALLREDUCE(temp,tmin,1,MPI_DOUBLE_PRECISION,MPI_MAX,MPI_COMM_WORLD,ierr)
      tmin = epsx/tmin

c----------------------------------
c make sure that t is between
c tmin and tmax
c----------------------------------

      tact  = 1.0
      tmax = 1.0e+10
      if (tact.le.tmin) then
         tact = tmin
         if (tact.gt.tmax) then
            tmin = tmax
         endif
      endif

      if (tact .gt. tmax) then
          tact = tmax
          ifail = 7
      endif

c----------------------------------
c compute new x
c----------------------------------
         temp = DNRM2(nn,dd,1)
         call MPI_ALLREDUCE(temp*temp,dnorm,1,MPI_DOUBLE_PRECISION,MPI_SUM,MPI_COMM_WORLD,ierr)
         dnorm = dsqrt(dnorm)

      if (myid .eq. 0) then
      print *,'bnc: initial stepsize tact = ',tact
      print *,'bnc: norm of dd            = ',dnorm
      endif

      do i = 1, nn
         xdiff(i) = xx(i) + tact*dd(i)
      end do

c----------------------------------
c save new x to file for offline version
c----------------------------------

 999  continue

      return

      end