anchor.diff:      Ir = 0
       Zpiv(1:Neqns) = 1
   
  -    do l = 1, Nttbr
  -      i = Irow(l)
  -      j = Jcol(l)
  -      if ( i<=0 .or. j<=0 ) then
  -        Ir = -1
  -        goto 100
  -      elseif ( i>Neqns .or. j>Neqns ) then
  -        Ir = 1
  -        goto 100
  -      endif
  -      if ( i==j ) Zpiv(i) = 0
  -    enddo
  -    do i = Neqns, 1, -1
  -      if ( Zpiv(i)==0 ) then
  -        Neqnsz = i
  -        exit
  -      endif
  -    enddo
  -    100 if ( IDBg/=0 ) write (6,"(20I3)") (Zpiv(i),i=1,Neqns)
  +    loop1: do
  +      do l = 1, Nttbr
  +        i = Irow(l)
  +        j = Jcol(l)
  +        if ( i<=0 .or. j<=0 ) then
  +          Ir = -1
  +          exit loop1
  +        elseif ( i>Neqns .or. j>Neqns ) then
  +          Ir = 1
  +          exit loop1
  +        endif
  +        if ( i==j ) Zpiv(i) = 0
  +      enddo
  +      do i = Neqns, 1, -1
  +        if ( Zpiv(i)==0 ) then
  +          Neqnsz = i
  +          exit
  +        endif
  +      enddo
  +      exit
  +    enddo loop1
  +    if ( IDBg/=0 ) write (6,"(20I3)") (Zpiv(i),i=1,Neqns)
     end subroutine ZPIVOT
   
     !======================================================================!
  
positive.code:     irch = 0
      inhd = 0
      node = Root
      100 jstrt = Xadj(node)
      jstop = Xadj(node+1) - 2
      if ( jstop>=jstrt ) then
        do j = jstrt, jstop
          irch = irch + 1
          Adjncy(j) = Rchset(irch)
          if ( irch>=Rchsze ) goto 200
        enddo
      endif
      link = Adjncy(jstop+1)
      node = -link
      if ( link>=0 ) then
        inhd = inhd + 1
        node = Nbrhd(inhd)
        Adjncy(jstop+1) = -node
      endif
      goto 100
  
      200 Adjncy(j+1) = 0
      do irch = 1, Rchsze
        node = Rchset(irch)
        if ( Marker(node)>=0 ) then
  
negative.code:           Marker(nabor) = -1
            Nhdsze = Nhdsze + 1
            Nbrhd(Nhdsze) = nabor
            loop1: do
              jstrt = Xadj(nabor)
              jstop = Xadj(nabor+1) - 1
              do j = jstrt, jstop
                node = Adjncy(j)
                nabor = -node
                if ( node<0 ) cycle loop1
                if ( node==0 ) exit
                if ( Marker(node)==0 ) then
                  Rchsze = Rchsze + 1
  