implicit real*8 (a-h,o-z)
      implicit integer (i-n)

      parameter (ixm1=1024,ixm2=ixm1/2,ixm3=ixm2/2,ixm4=ixm3/2,
     +            iym1=-32,iym2=iym1/2,iym3=iym2/2,iym4=iym3/2,
     +            iyp1=64 ,iyp2=iyp1/2,iyp3=iyp2/2,iyp4=iyp3/2)

      integer ns,printsteps,steps,screen,keyboard,arcfile,
     +        psifile,vortfile,sumfile,channeltype,asymfile,
     +        vasymfile
      integer central,upwind,ncupwind,laxwendroff,quickest,
     +        swapflow,archiveflow,changereynolds,changedt,
     +        changemethod,finish
      real*8 newvort,mean

      common/flow/psi (0:ixm1,iym1:iyp1),newvort(0:ixm1,iym1:iyp1),
     +            vort(0:ixm1,iym1:iyp1),oldvort(0:ixm1,iym1:iyp1),
     +            vincmax,            vincrement(0:ixm1,iym1:iyp1),
     +            u   (0:ixm1,iym1:iyp1),v      (0:ixm1,iym1:iyp1)

      common/params/currenttime,dt,reynolds,strouhal,
     +            pex,pey,cx,cy,
     +            timeresidual,mean,tolerance,method

      common/geometry/dx,dy,vfac,jv,ixc1,channeltype
      common/iofiles/inputfile,logfile,screen,keyboard,arcfile,
     +               psifile,vortfile,sumfile,asymfile,vasymfile

      common/defines/central,upwind,ncupwind,laxwendroff,quickest,
     +        swapflow,archiveflow,changereynolds,changedt,
     +        changemethod,finish
      common/run/ns,ns1,ns2,printsteps,steps,
     +           ix1,iy1,ix2,iy2,ix3,iy3,ix4,iy4

      real*8 z1(0:ixm1,iym1:iyp1),r1(0:ixm1,iym1:iyp1)
      real*8 z2(0:ixm2,iym2:iyp2),r2(0:ixm2,iym2:iyp2)
      real*8 z3(0:ixm3,iym3:iyp3),r3(0:ixm3,iym3:iyp3)
      real*8 z4(0:ixm4,iym4:iyp4),r4(0:ixm4,iym4:iyp4)