Sebastian Pop wrote:
Hi,
On Fri, Apr 16, 2010 at 02:14, Roberto Bagnara bagnara@cs.unipr.it wrote:
PPL 0.11 release candidates are available at
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