share/odepack/fortran/mdp.f

   1       subroutine mdp
   2      *     (k,ek,tail, v,l, head,last,next, mark)
   3 c***********************************************************************
   4 c  mdp -- purge inactive elements and do mass elimination
   5 c***********************************************************************
   6       integer  ek, tail,  v(*), l(*),  head(*), last(*), next(*),
   7      *   mark(*),  tag, free, li,vi,lvi,evi, s,ls,es, ilp,ilpmax
   8 c
   9 c----initialize tag
  10       tag = mark(ek)
  11 c
  12 c----for each vertex vi in ek
  13       li = ek
  14       ilpmax = last(ek)
  15       if (ilpmax.le.0)  go to 12
  16       do 11 ilp=1,ilpmax
  17         i = li
  18         li = l(i)
  19         vi = v(li)
  20 c
  21 c------remove vi from degree list
  22         if (last(vi).eq.0)  go to 3
  23           if (last(vi).gt.0)  go to 1
  24             head(-last(vi)) = next(vi)
  25             go to 2
  26    1        next(last(vi)) = next(vi)
  27    2      if (next(vi).gt.0)  last(next(vi)) = last(vi)
  28 c
  29 c------remove inactive items from element list of vi
  30    3    ls = vi
  31    4    s = ls
  32         ls = l(s)
  33         if (ls.eq.0)  go to 6
  34           es = v(ls)
  35           if (mark(es).lt.tag)  go to 5
  36             free = ls
  37             l(s) = l(ls)
  38             ls = s
  39    5      go to 4
  40 c
  41 c------if vi is interior vertex, then remove from list and eliminate
  42    6    lvi = l(vi)
  43         if (lvi.ne.0)  go to 7
  44           l(i) = l(li)
  45           li = i
  46 c
  47           k = k+1
  48           next(vi) = -k
  49           last(ek) = last(ek) - 1
  50           go to 11
  51 c
  52 c------else ...
  53 c--------classify vertex vi
  54    7      if (l(lvi).ne.0)  go to 9
  55             evi = v(lvi)
  56             if (next(evi).ge.0)  go to 9
  57               if (mark(evi).lt.0)  go to 8
  58 c
  59 c----------if vi is prototype vertex, then mark as such, initialize
  60 c----------overlap count for corresponding element, and move vi to end
  61 c----------of boundary list
  62                 last(vi) = evi
  63                 mark(evi) = -1
  64                 l(tail) = li
  65                 tail = li
  66                 l(i) = l(li)
  67                 li = i
  68                 go to 10
  69 c
  70 c----------else if vi is duplicate vertex, then mark as such and adjust
  71 c----------overlap count for corresponding element
  72    8            last(vi) = 0
  73                 mark(evi) = mark(evi) - 1
  74                 go to 10
  75 c
  76 c----------else mark vi to compute degree
  77    9            last(vi) = -ek
  78 c
  79 c--------insert ek in element list of vi
  80   10      v(free) = ek
  81           l(free) = l(vi)
  82           l(vi) = free
  83   11    continue
  84 c
  85 c----terminate boundary list
  86   12  l(tail) = 0
  87 c
  88       return
  89       end