2
Active
Objects and Messages
Nutshell summary:
•active means parallel, wait means blocking:
Gaining/losing concurrency is explicit, as is reentrancy.
Gaining/losing concurrency is explicit, as is reentrancy.
•Each active object conceptually runs on
its own thread.
•Method calls
from other threads are async messages processed serially Þ atomic w.r.t. each other, so no need to lock the object internally or externally. Default mainline is a
prioritized FIFO pump.
•Return values and out parameters are
futures (future<T>).
•Express thread/task lifetimes as object
lifetimes:
Exploit existing rich language semantics.
Exploit existing rich language semantics.
active
class C {
public:
void f() { … }
};
public:
void f() { … }
};
// in calling code, using a C object
active C c;
c.f(); // call is nonblocking
active C c;
c.f(); // call is nonblocking
… // this code can execute in parallel with c.f()