      subroutine nsfc
     *      (n, r, ic, ia,ja, jlmax,il,jl,ijl, jumax,iu,ju,iju,
     *       q, ira,jra, irac, irl,jrl, iru,jru, flag)
c*** subroutine nsfc
c*** symbolic ldu-factorization of nonsymmetric sparse matrix
c      (compressed pointer storage)
c
c
c       input variables.. n, r, ic, ia, ja, jlmax, jumax.
c       output variables.. il, jl, ijl, iu, ju, iju, flag.
c
c       parameters used internally..
c nia   - q     - suppose  m*  is the result of reordering  m.  if
c       -           processing of the ith row of  m*  (hence the ith
c       -           row of  u) is being done,  q(j)  is initially
c       -           nonzero if  m*(i,j) is nonzero (j.ge.i).  since
c       -           values need not be stored, each entry points to the
c       -           next nonzero and  q(n+1)  points to the first.  n+1
c       -           indicates the end of the list.  for example, if n=9
c       -           and the 5th row of  m*  is
c       -              0 x x 0 x 0 0 x 0
c       -           then  q  will initially be
c       -              a a a a 8 a a 10 5           (a - arbitrary).
c       -           as the algorithm proceeds, other elements of  q
c       -           are inserted in the list because of fillin.
c       -           q  is used in an analogous manner to compute the
c       -           ith column of  l.
c       -           size = n+1.
c nia   - ira,  - vectors used to find the columns of  m.  at the kth
c nia   - jra,      step of the factorization,  irac(k)  points to the
c nia   - irac      head of a linked list in  jra  of row indices i
c       -           such that i .ge. k and  m(i,k)  is nonzero.  zero
c       -           indicates the end of the list.  ira(i)  (i.ge.k)
c       -           points to the smallest j such that j .ge. k and
c       -           m(i,j)  is nonzero.
c       -           size of each = n.
c nia   - irl,  - vectors used to find the rows of  l.  at the kth step
c nia   - jrl       of the factorization,  jrl(k)  points to the head
c       -           of a linked list in  jrl  of column indices j
c       -           such j .lt. k and  l(k,j)  is nonzero.  zero
c       -           indicates the end of the list.  irl(j)  (j.lt.k)
c       -           points to the smallest i such that i .ge. k and
c       -           l(i,j)  is nonzero.
c       -           size of each = n.
c nia   - iru,  - vectors used in a manner analogous to  irl and jrl
c nia   - jru       to find the columns of  u.
c       -           size of each = n.
c
c  internal variables..
c    jlptr - points to the last position used in  jl.
c    juptr - points to the last position used in  ju.
c    jmin,jmax - are the indices in  a or u  of the first and last
c                elements to be examined in a given row.
c                for example,  jmin=ia(k), jmax=ia(k+1)-1.
c
      integer cend, qm, rend, rk, vj
      integer ia(*), ja(*), ira(*), jra(*), il(*), jl(*), ijl(*)
      integer iu(*), ju(*), iju(*), irl(*), jrl(*), iru(*), jru(*)
      integer r(*), ic(*), q(*), irac(*), flag
c
c  ******  initialize pointers  ****************************************
      np1 = n + 1
      jlmin = 1
      jlptr = 0
      il(1) = 1
      jumin = 1
      juptr = 0
      iu(1) = 1
      do 1 k=1,n
        irac(k) = 0
        jra(k) = 0
        jrl(k) = 0
   1    jru(k) = 0
c  ******  initialize column pointers for a  ***************************
      do 2 k=1,n
        rk = r(k)
        iak = ia(rk)
        if (iak .ge. ia(rk+1))  go to 101
        jaiak = ic(ja(iak))
        if (jaiak .gt. k)  go to 105
        jra(k) = irac(jaiak)
        irac(jaiak) = k
   2    ira(k) = iak
c
c  ******  for each column of l and row of u  **************************
      do 41 k=1,n
c
c  ******  initialize q for computing kth column of l  *****************
        q(np1) = np1
        luk = -1
c  ******  by filling in kth column of a  ******************************
        vj = irac(k)
        if (vj .eq. 0)  go to 5
   3      qm = np1
   4      m = qm
          qm =  q(m)
          if (qm .lt. vj)  go to 4
          if (qm .eq. vj)  go to 102
            luk = luk + 1
            q(m) = vj
            q(vj) = qm
            vj = jra(vj)
            if (vj .ne. 0)  go to 3
c  ******  link through jru  *******************************************
   5    lastid = 0
        lasti = 0
        ijl(k) = jlptr
        i = k
   6      i = jru(i)
          if (i .eq. 0)  go to 10
          qm = np1
          jmin = irl(i)
          jmax = ijl(i) + il(i+1) - il(i) - 1
          long = jmax - jmin
          if (long .lt. 0)  go to 6
          jtmp = jl(jmin)
          if (jtmp .ne. k)  long = long + 1
          if (jtmp .eq. k)  r(i) = -r(i)
          if (lastid .ge. long)  go to 7
            lasti = i
            lastid = long
c  ******  and merge the corresponding columns into the kth column  ****
   7      do 9 j=jmin,jmax
            vj = jl(j)
   8        m = qm
            qm = q(m)
            if (qm .lt. vj)  go to 8
            if (qm .eq. vj)  go to 9
              luk = luk + 1
              q(m) = vj
              q(vj) = qm
              qm = vj
   9        continue
            go to 6
c  ******  lasti is the longest column merged into the kth  ************
c  ******  see if it equals the entire kth column  *********************
  10    qm = q(np1)
        if (qm .ne. k)  go to 105
        if (luk .eq. 0)  go to 17
        if (lastid .ne. luk)  go to 11
c  ******  if so, jl can be compressed  ********************************
        irll = irl(lasti)
        ijl(k) = irll + 1
        if (jl(irll) .ne. k)  ijl(k) = ijl(k) - 1
        go to 17
c  ******  if not, see if kth column can overlap the previous one  *****
  11    if (jlmin .gt. jlptr)  go to 15
        qm = q(qm)
        do 12 j=jlmin,jlptr
          if (jl(j) - qm)  12, 13, 15
  12      continue
        go to 15
  13    ijl(k) = j
        do 14 i=j,jlptr
          if (jl(i) .ne. qm)  go to 15
          qm = q(qm)
          if (qm .gt. n)  go to 17
  14      continue
        jlptr = j - 1
c  ******  move column indices from q to jl, update vectors  ***********
  15    jlmin = jlptr + 1
        ijl(k) = jlmin
        if (luk .eq. 0)  go to 17
        jlptr = jlptr + luk
        if (jlptr .gt. jlmax)  go to 103
          qm = q(np1)
          do 16 j=jlmin,jlptr
            qm = q(qm)
  16        jl(j) = qm
  17    irl(k) = ijl(k)
        il(k+1) = il(k) + luk
c
c  ******  initialize q for computing kth row of u  ********************
        q(np1) = np1
        luk = -1
c  ******  by filling in kth row of reordered a  ***********************
        rk = r(k)
        jmin = ira(k)
        jmax = ia(rk+1) - 1
        if (jmin .gt. jmax)  go to 20
        do 19 j=jmin,jmax
          vj = ic(ja(j))
          qm = np1
  18      m = qm
          qm = q(m)
          if (qm .lt. vj)  go to 18
          if (qm .eq. vj)  go to 102
            luk = luk + 1
            q(m) = vj
            q(vj) = qm
  19      continue
c  ******  link through jrl,  ******************************************
  20    lastid = 0
        lasti = 0
        iju(k) = juptr
        i = k
        i1 = jrl(k)
  21      i = i1
          if (i .eq. 0)  go to 26
          i1 = jrl(i)
          qm = np1
          jmin = iru(i)
          jmax = iju(i) + iu(i+1) - iu(i) - 1
          long = jmax - jmin
          if (long .lt. 0)  go to 21
          jtmp = ju(jmin)
          if (jtmp .eq. k)  go to 22
c  ******  update irl and jrl, *****************************************
            long = long + 1
            cend = ijl(i) + il(i+1) - il(i)
            irl(i) = irl(i) + 1
            if (irl(i) .ge. cend)  go to 22
              j = jl(irl(i))
              jrl(i) = jrl(j)
              jrl(j) = i
  22      if (lastid .ge. long)  go to 23
            lasti = i
            lastid = long
c  ******  and merge the corresponding rows into the kth row  **********
  23      do 25 j=jmin,jmax
            vj = ju(j)
  24        m = qm
            qm = q(m)
            if (qm .lt. vj)  go to 24
            if (qm .eq. vj)  go to 25
              luk = luk + 1
              q(m) = vj
              q(vj) = qm
              qm = vj
  25        continue
          go to 21
c  ******  update jrl(k) and irl(k)  ***********************************
  26    if (il(k+1) .le. il(k))  go to 27
          j = jl(irl(k))
          jrl(k) = jrl(j)
          jrl(j) = k
c  ******  lasti is the longest row merged into the kth  ***************
c  ******  see if it equals the entire kth row  ************************
  27    qm = q(np1)
        if (qm .ne. k)  go to 105
        if (luk .eq. 0)  go to 34
        if (lastid .ne. luk)  go to 28
c  ******  if so, ju can be compressed  ********************************
        irul = iru(lasti)
        iju(k) = irul + 1
        if (ju(irul) .ne. k)  iju(k) = iju(k) - 1
        go to 34
c  ******  if not, see if kth row can overlap the previous one  ********
  28    if (jumin .gt. juptr)  go to 32
        qm = q(qm)
        do 29 j=jumin,juptr
          if (ju(j) - qm)  29, 30, 32
  29      continue
        go to 32
  30    iju(k) = j
        do 31 i=j,juptr
          if (ju(i) .ne. qm)  go to 32
          qm = q(qm)
          if (qm .gt. n)  go to 34
  31      continue
        juptr = j - 1
c  ******  move row indices from q to ju, update vectors  **************
  32    jumin = juptr + 1
        iju(k) = jumin
        if (luk .eq. 0)  go to 34
        juptr = juptr + luk
        if (juptr .gt. jumax)  go to 106
          qm = q(np1)
          do 33 j=jumin,juptr
            qm = q(qm)
  33        ju(j) = qm
  34    iru(k) = iju(k)
        iu(k+1) = iu(k) + luk
c
c  ******  update iru, jru  ********************************************
        i = k
  35      i1 = jru(i)
          if (r(i) .lt. 0)  go to 36
          rend = iju(i) + iu(i+1) - iu(i)
          if (iru(i) .ge. rend)  go to 37
            j = ju(iru(i))
            jru(i) = jru(j)
            jru(j) = i
            go to 37
  36      r(i) = -r(i)
  37      i = i1
          if (i .eq. 0)  go to 38
          iru(i) = iru(i) + 1
          go to 35
c
c  ******  update ira, jra, irac  **************************************
  38    i = irac(k)
        if (i .eq. 0)  go to 41
  39      i1 = jra(i)
          ira(i) = ira(i) + 1
          if (ira(i) .ge. ia(r(i)+1))  go to 40
          irai = ira(i)
          jairai = ic(ja(irai))
          if (jairai .gt. i)  go to 40
          jra(i) = irac(jairai)
          irac(jairai) = i
  40      i = i1
          if (i .ne. 0)  go to 39
  41    continue
c
      ijl(n) = jlptr
      iju(n) = juptr
      flag = 0
      return
c
c ** error.. null row in a
 101  flag = n + rk
      return
c ** error.. duplicate entry in a
 102  flag = 2*n + rk
      return
c ** error.. insufficient storage for jl
 103  flag = 3*n + k
      return
c ** error.. null pivot
 105  flag = 5*n + k
      return
c ** error.. insufficient storage for ju
 106  flag = 6*n + k
      return
      end
