pvm_getinst - returns the instance number in a group of a PVM process.
pvm_getinst takes a group name
and a PVM task identifier
and returns the unique instance number that corresponds to the input. It can be called by any task whether in the group or not. If pvm_getinst is successful,
will be >= 0. If some error occurs then
will be < 0.
inum = pvm_getinst( "worker", pvm_mytid() )