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Worksheet 24: arrive, awaitAdvance, and Shared Work

class Phaser

• register(): Adds a new unarrived party to this phaser.
• arrive(): Arrives at this phaser, without waiting for others to arrive.
• awaitAdvance(phase): Awaits the phase of this phaser to advance from the given phase value, returning immediately if the current phase is not equal to the given phase value or this phaser is terminated.

PhaserUtils

• awaitAdvanceForPhase(phaser, phase): awaits for the specified phaser's specified phase to be reached.

Draw The Computation Graph To The Right

s1
Phaser ph = new Phaser();
ph.register();
Future<Void> f = void_fork(()->{
    s2
    ph.arrive();
    s3
});
s4
PhaserUtils.awaitAdvanceForPhase(ph, 0);
s5
join(f);
s6

What can run in parallel with:

s1?

s2?

s3?

s4?

s5?

s6?

Iterative Averaging Shared Work

Imagine an array of length 20 below which is sliced up into 3 Ranges A, B, and C:

For Sliced Range A

• Which indices are "shared work" and must be processed before signaling arrival?

• Which indices are "local work" with greater flexibility?

For Sliced Range B

• Which indices are "shared work" and must be processed before signaling arrival?

• Which indices are "local work" with greater flexibility?

For Sliced Range C

• Which indices are "shared work" and must be processed before signaling arrival?

• Which indices are "local work" with greater flexibility?

Post Lecture

Synthesize today's class session

What is unclear?