The PETSc library  for the solution of partial differential equations has been instrumented by its authors to show all library routine calls. This enables them to better understand the relative effect on performance of various parts of the PETSc library. In Figure 10 one can see the nested states corresponding to the nested subroutine calls. Only a few states (PETSc functions) are visible in the states window, although the horizontal and vertical scrollbars for this window can be used to access the others. This is a case where the ability to tear off this window and display it in full size is useful.