anchor.diff:         open(newunit=lun, file=trim(outfile), status="old", position="append")
       endif
   
  -100 format(1x, g20.10, 1x, g20.10)
  -    write(unit=lun,fmt=100) t, mach_max
  +100 format(1x, g20.10, 1x, g20.10, 1x, g20.10)
  +    write(unit=lun,fmt=100) t, mach_max, mach_L2
   
       close (unit=lun)
   
  
positive.code:        rho = U%data(i,iudens)
         call eos(eos_input_e, p, e, rho)
  
         mach_max = max(mach_max, &
                        abs(U%data(i,iumomx)/U%data(i,iudens))/sqrt(gamma*p/rho))
      enddo
      
      outfile = trim(problem_name) // "_diag.out"
  
      if (n == 1) then
  
negative.code:     character (len=256) :: outfile
  
      mach_max = -1.d33
      mach_L2 = 0.0d0
  
      do i = U%grid%lo, U%grid%hi
  
  