anchor.diff:    end if
   
     call enforce_BCs
  +
  +  fx = 0.0_WP
  +  fy = 0.0_WP
  +  fz = 0.0_WP
   
     return
   end subroutine posvel_update
  
positive.code:     do j = 1, l
        nb = nbs(i,j)
        rhosum = rhosum + densitykernel(i,nb)
  
      end do
    rho(i) = rho(i) + rhosum
  
    end do
  
    return
  end subroutine compute_density
  
negative.code:       dz = pz(i) - pz(j)
        r2 = dx*dx + dy*dy + dz*dz
        h2 = h*h
  
        if(sqrt(r2).lt.1.0e-4_WP) r2 = 1.0e-4_WP**2
  
        if(r2 .gt. h2) then
          pressurekernel = 0.0_WP
        else
          c = 45.0_WP*mass/PI/h**5/rho(j)*(1.0_WP-sqrt(r2/h2))
          pressurekernel = c * BULK_MODULUS*0.5_WP &
                          *(rho(i)+rho(j)-2.0_WP*PARTICLE_DENSITY) &
                          *(1.0_WP - sqrt(r2/h2))/sqrt(r2/h2)
        end if
  
        return
  