The tickle function is a simple, extensible
interface that allows a task to poke at its local pvmd as it runs.
It is not formally specified,
but has proven to be very useful in debugging the system.
Tickle is accessible from the console (tickle command)
or libpvm.
Function pvm_tickle() sends a TM_TICKLE message to
the pvmd containing a short (maximum of ten) array of
integers and receives an array in reply.
The first element of the array is a subcommand,
and the remaining elements are parameters.
The commands currently defined are:
New tickle commands are generally added to the end of the list.