anchor.diff:                call TD_bufferData()
                 call TD_writeData(fvarts, .false.)
               endif
  -            
  +
               !Update the Mach Control
               if(exts .and. exMC) then
                 !Note: the function MC_updateState must be called after
  
positive.code:                rerr(:, 9)=rerr(:, 9)+(yold(:,3)-ybar(:,3))**2
                 rerr(:,10)=rerr(:,10)+(yold(:,4)-ybar(:,4))**2
              endif
             
  c.. writing ybar field if requested in each restart file		
              
              !here is where we save our averaged field.  In some cases we want to
              !write it less frequently		
              if( (irs >= 1) .and. (
       &          mod(lstep, ntout) == 0 .or. !Checkpoint
       &          istep == nstp) )then        !End of simulation
  
negative.code:                         y(:,7)  = yold(:,7)
                          ac(:,7) = zero 
                          if (ivconstraint .eq. 1) then
  c ... applying the volume constraint
  c
                             call solvecon (y,    x,      iBC,  BC, 
  