text: Subroutine graduk(ix, iy, iz, gradxk, gradyk, gradzk)
    Parameter (maxx=20, maxz=24)
    Parameter (rho0=0.168)
    Common /dd/rho(-maxx:maxx, -maxx:maxx, -maxz:maxz), rhop(-maxx:maxx, -maxx:maxx, -maxz:maxz), rhon(-maxx:maxx, -maxx:maxx, -maxz:maxz)
    Common /ss/inout(20)
    Save
    rxplus = rho(ix+1, iy, iz)
    rxmins = rho(ix-1, iy, iz)
    ryplus = rho(ix, iy+1, iz)
    rymins = rho(ix, iy-1, iz)
    rzplus = rho(ix, iy, iz+1)
    rzmins = rho(ix, iy, iz-1)
    gradxk = (rxplus-rxmins)/2.
    gradyk = (ryplus-rymins)/2.
    gradzk = (rzplus-rzmins)/2.
    Return
  End Subroutine graduk
  