[PPL-devel] New deterministic timeout facilities of the PPL and PWL

[Sebastian Pop]

On Mon, Jul 13, 2009 at 11:03, Roberto Bagnara<bagnara at cs.unipr.it> wrote:
> Sebastian Pop wrote:
>>
>> On Thu, Jul 9, 2009 at 07:12, Michael
>> Classen<michael.classen at uni-passau.de> wrote:
>>>
>>> Maybe it could also be possible to use the Parma Watchdog Library
>>> (PWL) for providing a timeout for the precise method and falling back
>>> to the more conservative method once a certain timeout is reached?
>>
>> Not in GCC.
>> This would make the compiler non deterministic.
>
> The new deterministic timeout facilities of the PPL and PWL (you need
> both) can be exploited (using the C language interface) by using the
> following functions:

Awesome!  Thanks!

> At the moment we cannot provide meaningful hints regarding the
> appropriate values to be given to these weight thresholds:
> they mainly depend on the particular application and on the
> particular problem instances considered. Some experimentation
> and tuning are unavoidable.
>
> Please test and let us know how it goes.  If you think you
> want this in time for GCC 4.5.0, please advise so that our
> release schedule matches the one of GCC.

We will play with PWL before integrating it in GCC.

I was thinking about starting the counter at the beginning of Graphite
when we initialize PPL and reseting it after code generation is done.
We may consider having the weight as a parameter of GCC with a default
value set such that we don't increase more than 10-20% the compile time
of SPEC Cpu2006 benchmarks.

Sebastian