Semantics of Futures in The Actor Model
In the Actor model, an expression of the form future
- When F receives a request R, then it checks to see if it has already received a response (that can either be a return value or a thrown exception) from evaluating
proceeding as follows: - If it already has a response V, then
- If V is a return value, then it is sent the request R.
- If V is an exception, then it is thrown to the customer of the request R.
- If it does not already have a response, then R is stored in the queue of requests inside the F.
- If it already has a response V, then
- When F receives the response V from evaluating
, then V is stored in F and - If V is a return value, then all of the queued requests are sent to V.
- If V is an exception, then it is thrown to the customer of the each queued request.
However, some futures can deal with requests in special ways to provide greater parallelism. For example, the expression 1 + future factorial(n) can create a new future that will behave like the number 1+factorial(n). This trick does not always work. For example the following conditional expression:
- if m>future factorial(n) then print("bigger") else print("smaller")
suspends until the future for factorial(n) has responded to the request asking if m is greater than itself.
Read more about this topic: Futures And Promises
Famous quotes containing the words futures, actor and/or model:
“One of the things that is most striking about the young generation is that they never talk about their own futures, there are no futures for this generation, not any of them and so naturally they never think of them. It is very striking, they do not live in the present they just live, as well as they can, and they do not plan. It is extraordinary that whole populations have no projects for a future, none at all.”
—Gertrude Stein (18741946)
“Change begets change. Nothing propagates so fast. If a man habituated to a narrow circle of cares and pleasures, out of which he seldom travels, step beyond it, though for never so brief a space, his departure from the monotonous scene on which he has been an actor of importance would seem to be the signal for instant confusion.... The mine which Time has slowly dug beneath familiar objects is sprung in an instant; and what was rock before, becomes but sand and dust.”
—Charles Dickens (18121870)
“She represents the unavowed aspiration of the male human being, his potential infidelityand infidelity of a very special kind, which would lead him to the opposite of his wife, to the woman of wax whom he could model at will, make and unmake in any way he wished, even unto death.”
—Marguerite Duras (b. 1914)