[dmd-concurrency] shared arrays

[Sean Kelly]

On Jan 14, 2010, at 5:04 AM, Steve Schveighoffer wrote:

> ----- Original Message ----
> 
>> From: Michel Fortin <michel.fortin at michelf.com>
>> 
>> Le 2010-01-14 à 7:10, Steve Schveighoffer a écrit :
>> 
>>> 
>>> What happens in cases like this:
>>> 
>>> shared(S)[] arr3;
>>> arr3[] = arr2[];
>>> 
>>> any ideas of how this can be resolved?  Should shared arrays enjoy all the 
>> operations that normal arrays have?
>> 
>> Well, you need a lock.
> 
> Whatever locks that must be taken must also be taken any time an array is accessed.
> 
> For instance you'd need to take the same lock when doing:
> 
> arr2[3].x = 5;
> 
> I don't think this is a workable solution.

This isn't bad for indexes ops, but taking the address of a shared array element is a huge problem, since information about the underlying array is lost.  This makes C-style array operations totally unfeasible for shared arrays, and this is when the data is simply shared, the atomic ops were only needed when the ref itself was shared.  Darnit.