anchor.diff:  ! ===================================== !
   program sph_run
     use state
  +  use posvel
     implicit none
   
     time = 0.0_WP
  
positive.code: 
    call init
  
    do while (time .lt. tfin)
      if(iter .gt. itermax) then
        print*, "Exceeded maximum iterations. Exiting..."
        stop
  
negative.code: ! ================================================ !
  ! Read in command line arguments and initialize    !
  ! ================================================ !
  subroutine init
    use state
    use constants
  