edu.rice.hj.api

Interface HjFuture<V>

Type Parameters:

V - the type of the value wrapped in the futureNb object.

All Known Subinterfaces:

HjDataDrivenFuture<V>

All Known Implementing Classes:

ParallelDataDrivenFuture, ParallelFuture

public interface HjFuture<V>

HJ also includes support for async tasks with return values in the form of futures . The statement, final HjFuture<T> f = futureNb(() -> Expr); creates a new child task to evaluate Expr that is ready to execute immediately. In this case, f contains a "futureNb handle" to the newly created task and the operation f.get() (also known as a force operation) can be performed to obtain the result of the futureNb task. If the futureNb task has not completed as yet, the task performing the f.get() operation blocks until the result of Expr becomes available. The get() operation also serves as a join on the futureNb task.

Author:

Shams Imam (shams@rice.edu)

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	HjFuture.CancelledException Exception returned

Method Summary

Modifier and Type	Method and Description
boolean	cancel() Attempts to cancel execution of this task.
boolean	failed() Return true if there was an exception while computing the value.
V	get() Returns the value wrapped in the futureNb.
boolean	resolved() Returns whether the futureNb has been resolved, i.e. the value has been computed.
V	safeGet() Returns the value wrapped in the Future.

Method Detail

get

V get()
throws SuspendableException

Returns the value wrapped in the futureNb.

If the futureNb task has not completed as yet, the task performing the get() operation blocks until the result of the futureNb becomes available.

Returns:

The value wrapped in the futureNb.

Throws:

HjFuture.CancelledException - when called on a futureNb which was successfully cancelled

SuspendableException

safeGet

V safeGet()

Returns the value wrapped in the Future.

It is illegal to perform a safeGet() operation on an empty Future (i.e. one that has not yet been resolved).

Returns:

The value wrapped in the futureNb.

resolved

boolean resolved()

Returns whether the futureNb has been resolved, i.e. the value has been computed. A failed future is also classified as resolved.

Returns:

whether the futureNb has been resolved, i.e. the value has been computed.

failed

boolean failed()

Return true if there was an exception while computing the value.

Returns:

true if there was an exception while computing the value.

cancel

boolean cancel()

Attempts to cancel execution of this task. If this task has not started when cancel is called, this task should never run its body. If the task has already started, then the task will not be interrupted and the task will run to completion.

Subsequent calls to failed() will always return true if this method returned true.

Returns:

false if the task could not be cancelled, typically because it has already completed normally or is being executed; true otherwise