- checkdone.cgi: a purely browser driven mechanism. It also means that
  certain actions never done unless trigered by the browser; anoying.

- causes of R stopping:
  1. done
  2. undetermined crash
  3. MPI errors: 
     3.1 LAM/MPI itself
     3.2 Rmpi

  In 1. and 2. we want to return. In 3. we want to keep trying.



- we could alternatively have a refresh that only shows results.html

- another mechanism which handles everything else. It keeps running
  forever until it is done (1., 2., or enough of 3.). Danger is that it
  might fail accidentally and no way to recover it? (could use a cgi, that
  just displays the html and checks the checker is running).

- this other mechanism is the one to launch the very first R process too.