Single Thread Continuation

[Robert Engels]

To elaborate - the producer knows when no more values are coming and marks the iterator as such. So the next calls to hasNext()/next() fail appropriately. That is trivial. 

The only “complex” part of the design is that the returned iterator is tracked with a weak reference by the producer. So if it goes out of scope the producer can be woken from the blocked/waiting state and clean up. 

> On Jul 4, 2023, at 7:01 AM, Robert Engels <rengels at ix.netcom.com> wrote:
> 
> 
> That is built into the Iterator interface. 
> 
>>> On Jul 4, 2023, at 4:05 AM, Alex Otenko <oleksandr.otenko at gmail.com> wrote:
>>> 
>> 
>> How does the generator tell the consumer that no more values are forthcoming? 
>> 
>>> On Mon, 3 Jul 2023, 12:38 Robert Engels, <rengels at ix.netcom.com> wrote:
>>> Believe me. Queues are all you need there is no memory leak and no need to “close”. The producer side uses a weak reference to the queue. When there are no more strong references the producer side can terminate. 
>>> 
>>> You can’t use a standard blocking queue for this - but the queue implementation is fairly trivial - with a wake-up thread that listens on the weak reference queue. 
>>> 
>>>>> On Jul 3, 2023, at 6:19 AM, Attila Kelemen <attila.kelemen85 at gmail.com> wrote:
>>>>> 
>>>> 
>>>>> 
>>>>> 2. We need to synchronize access to mutable state to avoid memory
>>>>>    hazards. This is a separate issue from synchronizing access to
>>>>>    mutable state to avoid correctness issues. With virtual threads on
>>>>>    a single platform thread, this goes away too (because it's always
>>>>>    the same thread observing memory operations; no barriers needed).
>>>>> 
>>>> 
>>>> That still seems incorrect to me (in principle, in practice it most likely will end up to be fine, but I just wouldn't rely on it), because the barrier is needed to prevent instruction reordering by the compiler, and you are not safe from that by using the same platform thread.
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