[PPL-devel] Thread Safety (continued)

[Enea Zaffanella]

Hello John.


On 10/07/2016 06:54 PM, John Paulson wrote:
> Hi Enea and Roberto,
>
> Thank you very much for all of the work you have done on threading 
> with PPL. I have a couple of questions about the current status of the 
> thread safety. A project I am currently working on needs to have 
> multiple threads working simultaneously on distinct PPL objects. Is 
> that possible with the new thread safe version?

Yes, it is possible.

If the PPL objects are distinct, so that there is no concurrent access 
to the *same* object, then things should not be difficult (e.g., no need 
at all for synchronization). You can have a look to the ppl_lcdd and 
ppl_lpsol demos or to the recently added tests in 
tests/Polyhedron/threadsafe*.cc

>
> I made an implementation of my current project where I fork processes 
> instead of using multiple threads. However, if I fork and have two 
> processes manipulating distinct PPL objects, I do not get a speedup by 
> a factor of two like I would expect. Is there anyway to get that type 
> of speedup?

If you use many process, then the PPL should be working fine "as is" 
(i.e., with thread-safety off).
As for the missing speedup, I doubt it has something to do with the library:
there should be something else going on, but I have no information to 
guess what it could be.

Cheers,
Enea.

>
>
> Best,
> John C. Paulson
>
>
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