[PPL-devel] PPL 0.11 ready for beta testing

[Albert Cohen]

Sebastian Pop wrote:
> Hi,
> 
> On Fri, Apr 16, 2010 at 02:14, Roberto Bagnara <bagnara at cs.unipr.it> wrote:
>> PPL 0.11 release candidates are available at
>>
>>  http://www.cs.unipr.it/ppl/Download/ftp/snapshots/
>>
> 
> I will update the Graphite automatic testers to use the PPL-0.11
> snapshots from now on.
> 
>> Several items in the NEWS file should be of interest to the
>> Graphite people.  Please give them a try.
>>
> 
>> o  New class PIP_Problem provides a Parametric Integer Programming
>>    (PIP) problem solver (mainly based on P. Feautrier's
>>    specification).  The implementation combines a parametric dual
>>    simplex algorithm using exact arithmetic with Gomory's cut
>>    generation.  Still under beta testing.
> 
> Using the PIP algorithm in the data dependence test, and in the loop
> fusion heuristic is high priority in my todo list.

Excellent. We need it right now with Konrad and Ramakrishna as well. 
Ramakrishna will be unavailable for 1 week, but Konrad can probably 
start helping you with it on Monday.

Our motivation is primarily to get rid of the spurious sequentialization 
  constraints due to scalar (1-element array) dependences. We have a 
method to do this WITHOUT expansion, in some loop transformation 
scenarios, including all the ones that are currently considered in 
Graphite. More specifically, for search-based techniques, we can weaken 
the condition of the Violated Dependence Analysis to handle live 
(unorderd) interval isolation constraints instead of (ordered) 
dependence constraints. We'll talk about or method in a future phone 
call. It is one more interesting research outcome of the Graphite 
project, after the pointer aliasing edge-clique cover problem!

>> o  New "deterministic" timeout computation facilities: it is now
>>    possible to set computational bounds (on the library calls taking
>>    exponential time) that do not depend on the actual elapsed time and
>>    hence are independent from the actual computation environment (CPU,
>>    operating system, etc.).  Still under beta testing.
> 
> I will also give this one a try: we have a testcase producing an
> exponential behavior for the conversion of polyhedra to powerset.
> I will try to use the deterministic timeout to solve this.
> 
>> If all goes well (i.e., the PPL bug-tracking system remains
>> clean) PPL 0.11 will be released on May 8, 2010.  Please
>> take into account that our past record indicates that,
>> despite our will to release more often, we are only able
>> to release once per year.
> 
> Thank you and the PPL development team for your excellent work.
> 
> Sebastian
> 
>