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)
“I suspect there isnt an actor alive who was able to truthfully answer his familys questions after his first days activity in his future profession.”
—Simone Signoret (19211985)
“Research shows clearly that parents who have modeled nurturant, reassuring responses to infants fears and distress by soothing words and stroking gentleness have toddlers who already can stroke a crying childs hair. Toddlers whose special adults model kindliness will even pick up a cookie dropped from a peers high chair and return it to the crying peer rather than eat it themselves!”
—Alice Sterling Honig (20th century)