Subtask states

[forax at univ-mlv.fr]

> From: "Alan Bateman" <alan.bateman at oracle.com>
> To: "Remi Forax" <forax at univ-mlv.fr>, "loom-dev" <loom-dev at openjdk.org>
> Sent: Saturday, September 27, 2025 9:33:42 AM
> Subject: Re: Subtask states

> On 26/09/2025 18:41, Remi Forax wrote:

>> Currently,
>> the interface Subtask defines 3 different states, but while the implementation
>> needs 3 states, I believe the interface only need 2.

>> Currently, having 3 states punished people that are using the API correctly, i.e
>> accessing the state when all the computations are done,
>> after join() is called, because for them, only two states are visible, but they
>> still need to write a code that takes can of the state
>> UNINITIALIZED.

>> I propose that state() can only return SUCCESS or FAILURE and throw an ISE if
>> the internal state is UNINITIALIZED given it means
>> that the API is not used correctly.

>> In the past, with the previous iteration of the design using inheritance instead
>> of delegation, the Subtask was not sealed,
>> so the internal state had to be exposed, but now that only the implementation of
>> STS can create a Subtask, the internal state UNINITIALIZED does not have to be
>> visible.

> Subtask has always been sealed. It has always had 3 states, nothing has changed,
> and nothing from the implementation has leaked into the API. So I'm a bit
> puzzled by your message. There is no outcome to report when a subtask is
> executing, was cancelled, or was forked after the scope was cancelled. The
> Subtask::state returns "UNAVAILABLE" for all these cases. It's easy to come up
> with examples where join returns a stream of subtasks in each of these states.
sorry, 
i forget that case, worst, i think you already explain that to me, again sorry. 

> Is your gripe with the onComplete method when writing a custom Joiner? That will
> only be called when the Subtask has completed and so is guaranteed to be in the
> SUCCESS or FAILED state?
yes, 
i think my mistake comes from the fact that for me the subtasks returned by STS.join() should all have been gone through onComplete, 
but this is not the case actually 

> -Alan
regards, 
Rém 
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