Concurrency between replays

[hchoaf]

Even if inputEngines and renderingEngines run concurrently, I assume while one engine is running, the other engine should pause (or at least in the critical section of run) as we might have race condition.

For instance, I ensured that inputEngine and renderingEngine do not encounter race condition and checked that situation like below does not occur.

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#Aa@#
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You hit a wall
Undo Quota: 2

However if I run the reference jar file, I see some printouts like below for multiple replays.

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#Aa@#
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#Aa@#
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#Aa@#
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Undo Quota: 2
Undo Quota: 2
Undo Quota: 2

I understand that there is no scheduling between the "replays". Does this mean engines from different replays might enter critical region together as long as gameState of each replay is not affected?

[Troublor]

I understand that there is no scheduling between the "replays". Does this mean engines from different replays might enter critical region together as long as gameState of each replay is not affected?

Yes, different replay uses different gameState instances, so they will not encounter race conditions.

[hchoaf]

Thanks for a quick reply.

For instance, I ensured that inputEngine and renderingEngine do not encounter race condition and checked that situation like below does not occur.

For this, is my understanding correct?

[Troublor]

Hmm, it depends on where you print the message. But essentially, the input engine and rendering engine of the same replay game should not enter the critical region that reads/writes the game state simultaneously.

[hchoaf]

@Troublor Thanks. I want to ask one more question from your answer.

How is "The game must be rendered at least once before the first action is performed (i.e., the initial state of the game must be rendered)." being tested in the hidden case?

I tried to create my own test case by collecting the thread IDs of each engine to see if the first threadID collected is the threadID of the rendering engine.

However, if the implementation does something (checks condition, waits for lock, etc) inside the while loop in run(), we might have something like below.
InputEngine fetches Action
RenderingEngine renders the map (initial state)
InputEngine processes the fetched action and update game state.

My concern is, the initial state is printed before any action processing, but the test will fail as the first 'thread' ran is the inputEngine thread in this case.

[Troublor]

We will check the order between invocations of processAction and render methods in the hidden tests.
An action is processed means processAction is called with this action.
The game is rendered means render method is called.
What is printed in the console does not matter.