Re: Ada 2012 automatic concurrency?

["John B. Matthews" <nospam@nospam.invalid>]

In article <af146e53-f736-4c59-8015-60a90d9f5fcf@googlegroups.com>,
 charleshixsn@earthlink.net wrote:

> In the RM I read (page 209):
> NOTES
> 1 Concurrent task execution may be implemented on multicomputers, 
> multiprocessors, or with interleaved execution on a single physical 
> processor. On the other hand, whenever an implementation can 
> determine that the required semantic effects can be achieved when 
> parts of the execution of a given task are performed by different 
> physical processors acting in parallel, it may choose to perform them 
> in this way.
> 
>     ----------------
> Does this imply that if I use protected types, that the code will 
> automatically be run concurrently on a multiprocessor system, or 
> might automatically be run concurrently?  

Perhaps, to the extent possible, but Ada 95 Rationale, Section 9.1 
Protected Types suggests that the approach was chosen, in part, to 
"enable the implementation of a synchronization mechanism that scales 
smoothly from a single processor to a multiprocessor."

Similar language appeared in the Ada 83 LRM, Section 9: Tasks, and it 
has remained unchanged since Ada 95, Section 9: Tasks and 
Synchronization.

> If so, does Gnat do this?

I don't know what it does currently, but I recall an older version 
targeting Mac OS 9: absent preemptive multi-tasking, the implementation 
used  an available FSU threads library. Protected types proved ideal for 
synchronizing access to the platform's single-threaded GUI library.

-- 
John B. Matthews
trashgod at gmail dot com
<http://sites.google.com/site/drjohnbmatthews>