This is the feedback thread for the second round of Community Review for DIP 1024, "Shared Atomics":

https://github.com/dlang/DIPs/blob/0093abce72fa803b9e4067db500171c634daa4a9/DIPs/DIP1024.md

All review-related feedback on and discussion of the DIP should occur in this thread. The review period will end at 11:59 PM ET on November 10, or when I make a post declaring it complete.

At the end of Round 2, if further review is deemed necessary, the DIP will be scheduled for another round of Community Review. Otherwise, it will be queued for the Final Review and Formal Assessment.

Anyone intending to post feedback in this thread is expected to be familiar with the reviewer guidelines:

https://github.com/dlang/DIPs/blob/master/docs/guidelines-reviewers.md

*Please stay on topic!*

Thanks in advance to all who participate.

On Sunday, 27 October 2019 at 12:20:49 UTC, Mike Parker wrote:
> This is the feedback thread for the second round of Community Review for DIP 1024, "Shared Atomics":
>
> [...]

Love this one! Some examples of code that’ll break would be nice to have i suppose. But otherwise can’t wait for this to get in!! 🎉

On Sun, Oct 27, 2019 at 5:25 AM Mike Parker via Digitalmars-d <digitalmars-d@puremagic.com> wrote:
>
> This is the feedback thread for the second round of Community Review for DIP 1024, "Shared Atomics":
>
> https://github.com/dlang/DIPs/blob/0093abce72fa803b9e4067db500171c634daa4a9/DIPs/DIP1024.md
>
> All review-related feedback on and discussion of the DIP should occur in this thread. The review period will end at 11:59 PM ET on November 10, or when I make a post declaring it complete.
>
> At the end of Round 2, if further review is deemed necessary, the DIP will be scheduled for another round of Community Review. Otherwise, it will be queued for the Final Review and Formal Assessment.
>
> Anyone intending to post feedback in this thread is expected to be familiar with the reviewer guidelines:
>
> https://github.com/dlang/DIPs/blob/master/docs/guidelines-reviewers.md
>
> *Please stay on topic!*
>
> Thanks in advance to all who participate.

Perfect. Thanks!

On 27.10.19 13:20, Mike Parker wrote:
> This is the feedback thread for the second round of Community Review for DIP 1024, "Shared Atomics":
> 
> https://github.com/dlang/DIPs/blob/0093abce72fa803b9e4067db500171c634daa4a9/DIPs/DIP1024.md 
> 
> 
> All review-related feedback on and discussion of the DIP should occur in this thread. The review period will end at 11:59 PM ET on November 10, or when I make a post declaring it complete.
> 
> At the end of Round 2, if further review is deemed necessary, the DIP will be scheduled for another round of Community Review. Otherwise, it will be queued for the Final Review and Formal Assessment.
> 
> Anyone intending to post feedback in this thread is expected to be familiar with the reviewer guidelines:
> 
> https://github.com/dlang/DIPs/blob/master/docs/guidelines-reviewers.md
> 
> *Please stay on topic!*
> 
> Thanks in advance to all who participate.

Looks good, except for this sentence:

"Atomic reads perform an acquire operation, writes perform a release operation, and read-modify-write performs an acquire, then a modification, and then a release. The result is sequentially consistent ordering, and each thread observes the same order of operations (total order)."

While atomics that act like this already provide some useful guarantees, this is not enough to ensure sequential consistency for more than two threads. This post explains it well: https://stackoverflow.com/a/14864466

Probably the sentence can just be dropped from the DIP, as it does not actually describe a language change, and core.atomic is more general than this anyway.

On Sun, Oct 27, 2019 at 2:25 PM Timon Gehr via Digitalmars-d <digitalmars-d@puremagic.com> wrote:
>
> On 27.10.19 13:20, Mike Parker wrote:
> > This is the feedback thread for the second round of Community Review for DIP 1024, "Shared Atomics":
> >
> > https://github.com/dlang/DIPs/blob/0093abce72fa803b9e4067db500171c634daa4a9/DIPs/DIP1024.md
> >
> >
> > All review-related feedback on and discussion of the DIP should occur in this thread. The review period will end at 11:59 PM ET on November 10, or when I make a post declaring it complete.
> >
> > At the end of Round 2, if further review is deemed necessary, the DIP will be scheduled for another round of Community Review. Otherwise, it will be queued for the Final Review and Formal Assessment.
> >
> > Anyone intending to post feedback in this thread is expected to be familiar with the reviewer guidelines:
> >
> > https://github.com/dlang/DIPs/blob/master/docs/guidelines-reviewers.md
> >
> > *Please stay on topic!*
> >
> > Thanks in advance to all who participate.
>
> Looks good, except for this sentence:
>
> "Atomic reads perform an acquire operation, writes perform a release operation, and read-modify-write performs an acquire, then a modification, and then a release. The result is sequentially consistent ordering, and each thread observes the same order of operations (total order)."
>
> While atomics that act like this already provide some useful guarantees, this is not enough to ensure sequential consistency for more than two threads. This post explains it well: https://stackoverflow.com/a/14864466
>
> Probably the sentence can just be dropped from the DIP, as it does not actually describe a language change, and core.atomic is more general than this anyway.

I had this thought too.
The atomic functions all accept arguments which define the fence
strategies anyway. The rules stated are not strictly necessary, or
actually true.

On 10/27/19 8:20 AM, Mike Parker wrote:
> This is the feedback thread for the second round of Community Review for DIP 1024, "Shared Atomics":
> 
> https://github.com/dlang/DIPs/blob/0093abce72fa803b9e4067db500171c634daa4a9/DIPs/DIP1024.md 
> 
> 
> All review-related feedback on and discussion of the DIP should occur in this thread. The review period will end at 11:59 PM ET on November 10, or when I make a post declaring it complete.
> 
> At the end of Round 2, if further review is deemed necessary, the DIP will be scheduled for another round of Community Review. Otherwise, it will be queued for the Final Review and Formal Assessment.
> 
> Anyone intending to post feedback in this thread is expected to be familiar with the reviewer guidelines:
> 
> https://github.com/dlang/DIPs/blob/master/docs/guidelines-reviewers.md
> 
> *Please stay on topic!*
> 
> Thanks in advance to all who participate.

This looks like exactly what I've been looking for in terms of shared! Thanks, I look very much forward to this being included. I'm a dunce when it comes to the atomic stuff, so I'll defer to more knowledgeable folks to cover those details (and hopefully provide some nice library/patterns).

-Steve

On Sunday, 27 October 2019 at 12:20:49 UTC, Mike Parker wrote:
> This is the feedback thread for the second round of Community Review for DIP 1024, "Shared Atomics":
>
> [...]

This is a much needed improvement. I look forward to fixing all the code it will deprecate as it's almost certainly wrong anyway.