An empty derivation of Struct.
Sometimes you only want to transmit a message without data, e.g. a
command to end the receiver. Then it would be to much overhead
(both for programming and for compiling) to define a new class for
all those messages. As a solution this class is defined. You
simply have to make instances of this class, constructed with the
corresponding StructId (It still has to be unique, see
vmStruct). As an example see the following:
Pvm::EmptyStruct Begin (BeginId);
Pvm::EmptyStruct End (EndId);
Pvm::Task Task;
Begin.Receive (Task);
End.Send (Task);