!***********************************************************************
!
!     file  lusol8b.f
!
!     lu8adc   lu8adr   lu8dlc   lu8dlr   lu8mod   lu8rpr
!
!     These routines call lu7asv and lu7bak in lusol7b.f.
!
! 08 Jun 2004: lusol8b.f is essentially lu8b.for from VMS days.
!              integer*4 changed to integer  .
! 15 Sep 2004: Test nout. gt. 0 to protect write statements.
*+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

      subroutine lu8adc( mode, m, n, v, w,
     $                   lena, luparm, parmlu,
     $                   a, indc, indr, ip, iq,
     $                   lenc, lenr, locc, locr,
     $                   inform, diag, vnorm )

      implicit           double precision (a-h,o-z)
      integer            luparm(30)
      double precision   parmlu(30), a(lena), v(m), w(n)
      integer            indc(lena), indr(lena), ip(m), iq(n)
      integer            lenc(n), lenr(m)
      integer            locc(n), locr(m)

!     ------------------------------------------------------------------
!     lu8adc  updates the LU factorization  A = L*U  when the vector
!     a(new)  is added to become the  n-th  column of  A.
!     The dimension of  A  is assumed to increase from  n-1  to  n
!     (not from  n  to  n+1).
!
!     If  mode = 1,  v(*)  must contain  a(new).
!     If  mode = 2,  v(*)  must satisfy  L*v = a(new).
!     On exit,  L*v = a(new)  in both cases.
!
!     The array  w(*)  is not used or altered.
!
!     On entry, all elements of  locc  are assumed to be zero.
!     On a successful exit (inform ne 7), this will again be true.
!
!     On exit:
!     inform =  0  if the rank of U stayed the same.
!     inform =  1  if the rank of U increased by 1.
!     inform =  7  if the update was not completed (lack of storage).
!
!     -- Feb 1985: Last  F66 version.
!     12 May 1988: First F77 version.  Now uses lu8rpc.
!     ------------------------------------------------------------------

      nout   = luparm(1)
      lprint = luparm(2)
      nrank  = luparm(16)

      ! Set  locc(n)  in case the user forgot.
      ! Then let lu8rpc do the job (but stop it from printing messages).

      locc(n)   =  0
      iq(n)     =  n
      luparm(2) = -1

      call lu8rpc( 0, mode, m, n, n, v, w,
     $             lena, luparm, parmlu,
     $             a, indc, indr, ip, iq,
     $             lenc, lenr, locc, locr,
     $             inform, diag, vnorm )

      if (inform .le. 0) then
         if (nrank .eq. n - 1) then
            if (nout. gt. 0  .and.  lprint .ge. 0)
     &           write(nout, 1100) m, n, diag, vnorm
         end if
      else if (inform .eq. 7) then
         if (nout. gt. 0  .and.  lprint .ge. 0)
     &        write(nout, 1700) lena
      end if

      luparm(2) = lprint
      return

 1100 format(/ ' lu8adc  warning.  Rank did not increase',
     $         ' after adding a column.'
     $       / ' m =', I8, '    n =', i8,
     $         '    diag =', 1p, e12.2, '    vnorm =', e12.2)
 1700 format(/ ' lu8adc  error...  Insufficient storage.',
     $         '    lena =', I8)

      end ! subroutine lu8adc

!+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

      subroutine lu8adr( m, n, w,
     $                   lena, luparm, parmlu,
     $                   a, indc, indr, ip, iq,
     $                   lenc, lenr, locc, locr,
     $                   inform, diag )

      implicit           double precision (a-h,o-z)
      integer            luparm(30)
      double precision   parmlu(30), a(lena), w(n)
      integer            indc(lena), indr(lena), ip(m), iq(n)
      integer            lenc(n), lenr(m)
      integer            locc(n), locr(m)

!     ------------------------------------------------------------------
!     lu8adr  updates the LU factorization  A = L*U  when the vector
!     w(*)  is added to become the  m-th  row of  A.
!     The dimension of  A  is assumed to increase from  m-1  to  m
!     (not from  m  to  m+1).
!
!     w(*)  is not altered.
!
!     On entry, all elements of  locc  are assumed to be zero.
!     On a successful exit (inform ne 7), this will again be true.
!
!     On exit:
!     inform =  0  if the rank of U stayed the same.
!     inform =  1  if the rank of U increased by 1.
!     inform =  7  if the update was not completed (lack of storage).
!
!     -- Feb 1985: Last  F66 version.
!     17 May 1988: First F77 version.
!     ------------------------------------------------------------------

      parameter        ( zero = 0.0d+0 )

      nout   = luparm(1)
      lprint = luparm(2)
      nrank  = luparm(16)
      lenl   = luparm(23)
      lenu   = luparm(24)
      lrow   = luparm(25)
      small  = parmlu(3)
      diag   = zero
      nrank1 = nrank + 1

      ! Compress row file if necessary.

      minfre = n
      nfree  = lena - lenl - lrow
      if (nfree .ge. minfre) go to 100
      call lu1rec( m, .true., luparm, lrow, ilast,
     $             lena, a, indr, lenr, locr )
      nfree  = lena - lenl - lrow
      if (nfree .lt. minfre) go to 970

      ! Pack the nonzeros of  w  at the end of the row file.
      ! Go backwards in order to set  kfirst.

  100 locr(m) = lrow + 1
      ip(m)   = m
      lenr(m) = 0

      do 120 k = n, 1, -1
         j          = iq(k)
         if (abs( w(j) ) .le. small) go to 120
         kfirst     = k
         lrow       = lrow + 1
         a(lrow)    = w(j)
         indr(lrow) = j
  120 continue

      lenw    = lrow + 1 - locr(m)
      lenu    = lenu + lenw
      lenr(m) = lenw

!     ------------------------------------------------------------------
!     Triangularize the new row.
!     ------------------------------------------------------------------

      if (lenw .gt. 0) then

         ! Swap the new row into position nrank1.

         ip(m)      = ip(nrank1)
         ip(nrank1) = m

         ! Perform a forward sweep to eliminate subdiagonal elements.

         if (kfirst .le. nrank1) then
            call lu7for( m, n, kfirst, nrank1,
     $                   lena, luparm, parmlu,
     $                   lenl, lenu, lrow,
     $                   a, indc, indr, ip, iq, lenr, locc, locr,
     $                   inform, diag )
            if (inform .eq. 7) go to 970
         end if

         ! See if the rank increases.

         if (nrank .lt. n) then
            nrank  = nrank1
            call lu7rnk( m, n, 0,
     $                   lena, luparm, parmlu,
     $                   lenl, lenu, lrow, nrank,
     $                   a, indc, indr, ip, iq, lenr, locc, locr,
     $                   inform, diag )
         end if
      end if

!     ------------------------------------------------------------------
!     Set inform for normal exit.
!     ------------------------------------------------------------------
      if (nrank .ne. nrank1) then
         inform = 0
         if (nrank .eq. m - 1) then
            if (nout. gt. 0  .and.  lprint .ge. 0)
     &           write(nout, 1100) m, n, diag
         end if
      else
         inform = 1
      end if
      go to 990

      ! Not enough storage.

  970 inform = 7
      if (nout. gt. 0  .and.  lprint .ge. 0)
     &     write(nout, 1700) lena

      ! Exit.

  990 luparm(10) = inform
      luparm(15) = luparm(15) + 1
      luparm(16) = nrank
      luparm(23) = lenl
      luparm(24) = lenu
      luparm(25) = lrow
      return

 1100 format(/ ' lu8adr  warning.  Rank did not increase',
     $         ' after adding a row.'
     $       / ' m =', i8, '    n =', i8,
     $         '    diag =', 1p, e12.2)
 1700 format(/ ' lu8adr  error...  Insufficient storage.',
     $         '    lena =', i8)

      end ! subroutine lu8adr

!+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

      subroutine lu8dlc( m, n, jdel,
     $                   lena, luparm, parmlu,
     $                   a, indc, indr, ip, iq,
     $                   lenc, lenr, locc, locr,
     $                   inform )

      implicit           double precision (a-h,o-z)
      integer            luparm(30)
      double precision   parmlu(30), a(lena)
      integer            indc(lena), indr(lena), ip(m), iq(n)
      integer            lenc(n), lenr(m)
      integer            locc(n), locr(m)

!     ------------------------------------------------------------------
!     lu8dlc  updates the LU factorization  A = L*U  when column  jdel
!     is deleted.  The dimension of  A  decreases from  n  to  n-1.
!     The column permutation  iq(*)  and the column indices in  U
!     are altered accordingly.
!
!     NOTE:  The calling program must change  n  to  n-1.
!
!     In some cases it may be more efficient to use  lu8rpc  to
!     replace column  jdel  by zero, leaving it in the current position.
!
!     On entry, all elements of  locc  are assumed to be zero.
!     On a successful exit (inform ne 7), this will again be true.
!
!     On exit:
!     inform = -1  if the rank of U decreased by 1.
!     inform =  0  if the rank of U stayed the same.
!     inform =  7  if the update was not completed (lack of storage).
!
!     -- Feb 1985: Last  F66 version.
!     17 May 1988: First F77 version.
!     ------------------------------------------------------------------

      nout   = luparm(1)
      lprint = luparm(2)
      nrank  = luparm(16)
      lenl   = luparm(23)
      lenu   = luparm(24)
      lrow   = luparm(25)
      n1     = n - 1
      if (jdel .lt. 1) go to 980
      if (jdel .gt. n) go to 980

      ! Remove column jdel from U, and set kdel so that iq(kdel) = jdel.

      call lu7zap( m, n, jdel, kdel,
     $             lena, lenu, lrow, nrank,
     $             a, indr, ip, iq, lenr, locr )

      ! Renumber columns of  U  that are to the right of column  jdel.
      ! In effect, those columns are shifted one place to the left.

      if (jdel .lt. n) then
         do k = 1, nrank
            i      = ip(k)
            lr1    = locr(i)
            lr2    = lr1 + lenr(i) - 1

            do l = lr1, lr2
               j     = indr(l)
               if (j .gt. jdel) indr(l) = j - 1
            end do
         end do

         do k = 1, n
            j     = iq(k)
            if (j .gt. jdel) iq(k) = j - 1
         end do
      end if

      ! Perform cyclic permutations to move column kdel to the end
      ! and the corresponding row to position nrank.
      ! Then eliminate the resulting row spike.

      call lu7cyc( kdel, nrank, ip )
      call lu7cyc( kdel, n    , iq )

      call lu7for( m, n1, kdel, nrank,
     $             lena, luparm, parmlu,
     $             lenl, lenu, lrow,
     $             a, indc, indr, ip, iq, lenr, locc, locr,
     $             inform, diag )
      if (inform .eq. 7) go to 970

      ! See if the rank decreased.

      CALL LU7RNK( M, N1, 0,
     $             LENA, LUPARM, PARMLU,
     $             LENL, LENU, LROW, NRANK,
     $             A, INDC, INDR, IP, IQ, LENR, LOCC, LOCR,
     $             INFORM, DIAG )
      go to 990

      ! Not enough storage.

  970 inform = 7
      if (nout. gt. 0  .and.  lprint .ge. 0)
     &     write(nout, 1700) lena
      go to 990

      ! jdel  is out of range.

  980 inform = 8
      if (nout. gt. 0  .and.  lprint .ge. 0)
     &     write(nout, 1800) m, n, jdel

      ! Exit.

  990 luparm(10) = inform
      luparm(15) = luparm(15) + 1
      luparm(16) = nrank
      luparm(23) = lenl
      luparm(24) = lenu
      luparm(25) = lrow
      return

 1700 format(/ ' lu8dlc  error...  Insufficient storage.',
     $         '    lena =', i8)
 1800 format(/ ' lu8dlc  error...  jdel  is out of range.',
     $         '    m =', i8, '    n =', i8, '    jdel =', i8)

      end ! subroutine lu8dlc

!+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++


!+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

      subroutine lu8mod( mode, m, n, beta, v, w,
     $                   lena, luparm, parmlu,
     $                   a, indc, indr, ip, iq,
     $                   lenc, lenr, locc, locr,
     $                   lenlv, inform )

      implicit           double precision (a-h,o-z)
      integer            luparm(30)
      double precision   parmlu(30), a(lena), v(m), w(n)
      integer            indc(lena), indr(lena), ip(m), iq(n)
      integer            lenc(n), lenr(m)
      integer            locc(n), locr(m)
      integer            lenlv(3)
!     ------------------------------------------------------------------
!     lu8mod  updates the LU factorization  A = L*U  when the
!     m by n matrix  A  is subjected to a rank-one modification
!     to become
!                    A  +  beta * v * w(transpose)
!     for the given scalar  beta  and vectors  v, w.
!
!     If mode = 1, v(*) must contain the vector  v.
!                  On exit, v(*) will contain  y  satisfying  L*y = v.
!
!     If MODE = 2, v(*) must already contain   y  satisfying  L*y = v.
!
!     In both cases, w(*) is unaltered.
!
!     On entry, the elements of  locc  are assumed to be zero.
!     On a successful exit (inform ne 7), this will again be true.
!
!     On exit:
!     inform = -1  if the rank of U decreased by 1.
!     inform =  0  if the rank of U stayed the same.
!     inform =  1  if the rank of U increased by 1.
!     inform =  7  if the update was not completed (lack of storage).
!
!     -- Mar 1985: Last  F66 version.
!     18 May 1988: First F77 version.
!     ------------------------------------------------------------------

      logical            singlr
   
      nout   = luparm(1)
      lprint = luparm(2)
      nrank  = luparm(16)
      lenl   = luparm(23)
      lenu   = luparm(24)
      lrow   = luparm(25)
      small  = parmlu(3)
      utol1  = parmlu(4)
      nrank0 = nrank
      lenl0  = lenl
      singlr = .FALSE.
      ! If necessary, solve  L*v(new) = v.

      if (mode .eq. 1) then
         call lu6sol( 1, m, n, v, w, lena, luparm, parmlu,
     $                a, indc, indr, ip, iq, lenc, lenr, locc, locr,
     $                inform )
      end if

!     ------------------------------------------------------------------
!     Find the first nonzero in  w  (in pivotal column order).
!     ------------------------------------------------------------------
      do k = 1, n
         kfirst = k
         j      = iq(k)
         if (abs( w(j) ) .gt. small) go to 120
      end do
      go to 900

!     ------------------------------------------------------------------
!     Eliminate any nonzeros in  v  below the trapezoid.
!     --- This shouldn't ever happen. REMEMBER TO ERASE THIS ------
!     ------------------------------------------------------------------
  120 if (nrank .lt. m) then
         jelm   = 0

         call lu7elm( m, n, jelm, v,
     $                lena, luparm, parmlu,
     $                lenl, lenu, lrow, nrank,
     $                a, indc, indr, ip, iq, lenr, locc, locr,
     $                inform, diag )

         if (inform .eq. 1) nrank = nrank+1;
         if (inform .eq. 7) go to 970

      end if

!     ------------------------------------------------------------------
!     Find the last nonzero in  v  (in pivotal row order).
!     ------------------------------------------------------------------
      do k = nrank, 1, -1
         klast  = k
         i      = ip(k)
         if (abs( v(i) ) .gt. small) go to 220
      end do
      go to 900

!     ------------------------------------------------------------------
!     Perform a backward sweep of eliminations to reduce part of  v
!     to a multiple of the unit vector  e(iw),  where  iw = ip(klast).
!     Elements  ip(kfirst+1),  ip(kfirst+2),  ...,  ip(klast)  of  v
!     are involved.
!     L, U  and  ip  are updated accordingly.
!     U  will then be trapezoidal except for row  iw = ip(klast).
!     ------------------------------------------------------------------
  220 if (kfirst+1 .lt.  klast) then
         call lu7bak( m, n, kfirst, klast, v,
     $                lena, luparm, parmlu,
     $                lenl, lenu, lrow,
     $                a, indc, indr, ip, iq, lenr, locc, locr,
     $                inform )
         if (inform .ne. 0) go to 970
      end if
      lenlv(1) = lenl - lenl0
      lenl0 = lenl
!     ------------------------------------------------------------------
!     Pack the nonzeros of  w  in pivotal order in front of  L.
!     (We will treat the packed  w  much like a normal row of  U.)
!     Set markers on  w  and initialize the corresponding
!     elements of  indc(*),  which are later used by  lu7asv.
!     ------------------------------------------------------------------

      lfree  = lena - lenl
      minfre = n + 1 - kfirst
      nfree  = lfree - lrow
      if (nfree .ge. minfre) go to 310
      call lu1rec( m, .true., luparm, lrow, ilast,
     $             lena, a, indr, lenr, locr )
      nfree  = lfree - lrow
      if (nfree .lt. minfre) go to 970

  310 lw     = lfree + 1

      do 320   k  = n, kfirst, -1
         j        = iq(k)
         if (abs( w(j) ) .le. small) go to 320
         lw       = lw - 1
         a(lw)    = w(j)
         indr(lw) = j
         indc(lw) = 0
         locc(j)  = lw
  320 continue

      lw1    = lw
      lw2    = lfree
      lenw   = lw2 + 1 - lw1
      lfree  = lfree - lenw

!     ------------------------------------------------------------------
!     Add multiples of  w  to the first  kfirst  rows of  U.
!     (This does not alter the trapezoidal form of  U.)
!     ------------------------------------------------------------------

      do 450 k  = 1, kfirst
         iv     = ip(k)
         cv     = v(iv)
         if (abs( cv ) .le. small) go to 450

!        ===============================================================
!        Compress storage if necessary, so there will be room if
!        row  iv  has to be moved to the end.
!        ===============================================================
         minfre = n
         nfree  = lfree - lrow
         if (nfree .ge. minfre) go to 420
         call lu1rec(m, .true., luparm, lrow,
     $               ilast, lena, a,indr,lenr, locr)
         nfree  = lfree - lrow
         if (nfree .lt. minfre) go to 970

!        ===============================================================
!        Set  v  =  v  +  wmult * w.
!        ===============================================================
  420    wmult  = beta * cv
         call lu7asv( m, n, iv, lenw, lw1, lw2, k, wmult,
     $                lena, luparm, parmlu,
     $                lenu, lrow,
     $                a, indc, indr, lenr, locc, locr )
  450 continue

!     ------------------------------------------------------------------
!     Add a multiple of  w  to row  iw  of  U.
!     ------------------------------------------------------------------

      if (kfirst .lt. klast) then
         minfre = n
         nfree  = lfree - lrow
         if (nfree .ge. minfre) go to 500
         call lu1rec( m, .true., luparm, lrow, ilast,
     $                lena, a,indr,lenr,locr )
         nfree  = lfree - lrow
         if (nfree .lt. minfre) go to 970

  500    iw     = ip(klast)
         marker = m + 1
         wmult  = beta * v(iw)
         call lu7asv( m, n, iw, lenw, lw1, lw2, marker, wmult,
     $                lena, luparm, parmlu,
     $                lenu, lrow,
     $                a, indc, indr, lenr, locc, locr )
      end if

!     ------------------------------------------------------------------
!     Cancel the markers on  w.
!     ------------------------------------------------------------------
      do lw  = lw1, lw2
         jw       = indr(lw)
         locc(jw) = 0
      end do
!     ------------------------------------------------------------------
!     Apply a forward sweep to eliminate the nonzeros in row  iw.
!     ------------------------------------------------------------------
      if (kfirst .gt. klast) then
         if (klast .lt. nrank) go to 900
      else
         call lu7for( m, n, kfirst, klast,
     $                lena, luparm, parmlu,
     $                lenl, lenu, lrow,
     $                a, indc, indr, ip, iq, lenr, locc, locr,
     $                inform, diag )
         if (inform .eq. 7) go to 970
         lenlv(2) = lenl - lenl0
         lenl0 = lenl
      end if

!     ------------------------------------------------------------------
!     Test for singularity in column klast (if klast .le. nrank).
!     The code is similar to part of lu8rpc with klast in place of krep.
!     ------------------------------------------------------------------

      if (klast .le. nrank) then
         diag   = zero
         iw     = ip(klast)
         singlr = lenr(iw) .eq. 0

         if (.not. singlr) then
            l1     = locr(iw)
            j1     = indr(l1)
            singlr = j1 .ne. jrep

            if (.not. singlr) then
               diag   = a(l1)
               singlr = abs( diag ) .le. utol1
            end if
         end if

         if ( singlr  .and.  klast .lt. nrank ) then

            ! Perform cyclic permutations to move column klast
            ! to the end and the corresponding row to position nrank.
            ! Then eliminate the resulting row spike.

            call lu7cyc( klast, nrank, ip )
            call lu7cyc( klast, n    , iq )

            call lu7for( m, n, klast, nrank,
     $                   lena, luparm, parmlu,
     $                   lenl, lenu, lrow,
     $                   a, indc, indr, ip, iq, lenr, locc, locr,
     $                   inform, diag )
            lenlv(3) = lenl - lenl0
            if (inform .eq. 7) go to 970
         end if
         ! Find the best column to be in position nrank.
         ! If nothing satisfactory exists, nrank will be decreased.

         jsing  = 0
         call lu7rnk( m, n, jsing,
     $                lena, luparm, parmlu,
     $                lenl, lenu, lrow, nrank,
     $                a, indc, indr, ip, iq, lenr, locc, locr,
     $                inform, diag )
      end if 
!     ------------------------------------------------------------------
!     Set inform for exit.
!     ------------------------------------------------------------------

  900 if (nrank .eq. nrank0) then
         inform =  0
      else if (nrank .lt. nrank0) then
         inform = -1
      else
         inform =  1
      end if
      go to 990

      ! Not enough storage.

  970 inform = 7
      if (nout. gt. 0  .and.  lprint .ge. 0)
     &     write(nout, 1700) lena

      ! Exit.

  990 luparm(10) = inform
      luparm(15) = luparm(15) + 1
      luparm(16) = nrank
      luparm(23) = lenl
      luparm(24) = lenu
      luparm(25) = lrow
      return

 1700 format(/ ' lu8mod  error...  Insufficient storage.',
     $         '    lena =', i8)

      end ! subroutine lu8mod

!+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

      subroutine lu8rpr( mode1, mode2, m, n, irep, v, w, wnew,
     $                   lena, luparm, parmlu,
     $                   a, indc, indr, ip, iq,
     $                   lenc, lenr, locc, locr,
     $                   lenlv, li, lj, lv, 
     $                   inform )

      implicit           double precision (a-h,o-z)
      integer            luparm(30)
      double precision   parmlu(30), a(lena), v(m), w(n), wnew(n)
      integer            indc(lena), indr(lena), ip(m), iq(n)
      integer            lenc(n), lenr(m)
      integer            locc(n), locr(m)
      integer            lenlv(3),li(3*m), lj(3*m)
      double precision   lv(3*m)

!     ------------------------------------------------------------------
!     lu8rpr  updates the LU factorization  A = L*U  when row  irep
!     (a vector  w(old)) is replaced by some vector  w(new).
!     The update is implemented as the rank-one modification
!
!           A(new)  =  A  -  e(irep) * ( w(old) - w(new) )'
!
!     with variations determined by  mode1  and  mode2  as follows.
!
!     mode1
!     -----
!       0     w(old)  is assumed to be zero.
!             w(*)    need not be set on entry, but will be altered.
!
!       1     w(old)  is assumed to be unknown.  it will be computed
!                     from the LU factors of  A.
!             w(*)    need not be set on entry, but will be altered.
!
!       2     w(*)    must contain  w(old).
!                     On exit, it will contain  w(old) - w(new).
!
!       3     w(*)    must contain  w(old) - w(new).  It is not altered.
!                     wnew(*) is not used.
!
!       4     w(*)    must contain  w(new) - w(old).  It is not altered.
!                     wnew(*) is not used.
!
!     If  mode1 = 3 or 4,  mode2  is not used.  It may be set to 0 or 1.
!     Otherwise,  mode2  is used as follows.
!
!     mode2
!     -----
!       0     w(new)  is assumed to be zero.   wnew(*)  is not used.
!
!       1     wnew(*) must contain the new row.
!
!     v(*)    is a work array of length  m.
!     On entry, all elements of  locc  are assumed to be zero.
!     On a successful exit (inform ne 7), this will again be true.
!
!
!     On exit:
!     inform = -1  if the rank of U decreased by 1.
!     inform =  0  if the rank of U stayed the same.
!     inform =  1  if the rank of U increased by 1.
!     inform =  7  if the update was not completed (lack of storage).
!     inform =  8  if jrep is not between 1 and n.
!
!     -- Mar 1985: Last  F66 version.
!     18 May 1988: First F77 version.
!     ------------------------------------------------------------------

      parameter        ( zero = 0.0d+0,  one = 1.0d+0 )
      
      lenL0 = luparm(23)     
      lenlv(1:3) = 0
      nout   = luparm(1)
      lprint = luparm(2)
      if (irep .lt. 1) go to 980
      if (irep .gt. m) go to 980

      if (mode1 .eq. 0) then

         ! The old row  irep  is zero.

         do j = 1, n
            w(j) = zero
         end do
      else if (mode1 .eq. 1) then

         ! Compute row irep as the vector  w  =  A(transpose) * e(irep).

         do i = 1, m
            v(i)  = zero
         end do
         v(irep) = one
         call lu6mul( 6, m, n, v, w, lena, luparm, parmlu,
     $                a, indc, indr, ip, iq, lenc, lenr, locc, locr )
      end if

      if (mode1 .le. 2) then

         ! Compute the difference except if  wnew = 0.

         if (mode2 .gt. 0) then
            do j = 1, n
               w(j)  = w(j) - wnew(j)
            end do
         end if
      end if

!     ------------------------------------------------------------------
!     Set  v = a unit vector  and do the rank-one modification
!     (but don't let lu8mod print anything).
!     ------------------------------------------------------------------

      do i = 1, m
         v(i)  = zero
      end do

      v(irep)   =   one
      beta      = - one
      if (mode1 .eq. 4) beta = one
      luparm(2) = - 1

      call lu8mod( 1, m, n, beta, v, w,
     $             lena, luparm, parmlu,
     $             a, indc, indr, ip, iq, lenc, lenr, locc, locr,
     $             lenlv, inform )
      if (inform .eq. 7) go to 970

      lenlv_total = lenlv(1) + lenlv(2) + lenlv(3)
      do j =1, lenlv_total
         li(j) = indc(lena-lenL0-j+1)
         lj(j) = indr(lena-lenL0-j+1)
         lv(j) = a(lena-lenL0-j+1)
      end do
      go to 990

      ! Not enough storage.

  970 inform = 7
      if (nout. gt. 0  .and.  lprint .ge. 0)
     &     write(nout, 1700) lena
      go to 990

      ! irep  is out of range.

  980 inform = 8
      if (nout. gt. 0  .and.  lprint .ge. 0)
     &     write(nout, 1800) m, n, irep

      ! Exit.

  990 luparm(2)  = lprint
      luparm(10) = inform
      return

 1700 format(/ ' lu8rpr  error...  Insufficient storage.',
     $         '    lena =', i8)
 1800 format(/ ' lu8rpr  error...  irep  is out of range.',
     $         '    m =', i8, '    n =', i8, '    irep =', i8)

      end ! subroutine lu8rpr

