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Re: [p2-dev] Projector weight function

Here is a non final copy of the article 

Attachment: lash2010.pdf
Description: Adobe PDF document

On 2011-07-20, at 5:26 PM, Langhuth, Eckart wrote:

> Hi Daniel,
> 
> thanks for reply.
> Just for clarification. I do not assume the current behavior as a bug.
> But I failed to find information regarding the objective function definition used.
> So I raised the question here really out of curiosity.
> Unfortunately the provided documentation link does not work for me. (404)
> 
> The reported Tycho problem should be fixed in Tycho anyway.
> 0.0.0 versions used in the feature.xml should be strictly resolved to the latest available version. 
> 
> Best regards, 
> Eckart
> 
> On Behalf Of Daniel Le Berre
> Sent: Mittwoch, 20. Juli 2011 15:44
> 
> Hi Eckart,
> 
> Thanks for the bug report. We will take a closer look at your particular case.
> 
> The way the objective function is defined in p2 is described here:
> http://www.cril.univ-artois.fr/spip/publications/lash2010.pdf
> 
> The behavior you observe might be expectable.
> 
> Suppose that you have package x version 1 and x version 2
> 
> Version 1 has no dependencies and version 2 has dependencies on y z u and v.
> 
> Suppose we have a minimal penalty of 1 for installing a package (to avoid installing a non necessary package).
> 
> In that case, if the penalty for installing an "old" package for x1 is 4 for instance, then the solver prefers to install x1 for a penalty of 4 instead of x2 for a penalty of 5 (1 for each x2, y,,z, u, v).
> 
> Note that with a bigger penalty for old versions, we could still install x2.
> 
> I will check in your bug report if this is really what happens in your case.
> 
> Cheers,
> 
> Daniel
> Le 20 juil. 2011 à 13:22, Langhuth, Eckart a écrit :
> 
>> Hi,
>> 
>> As requested I created a p2 bug for this issue
>> https://bugs.eclipse.org/bugs/show_bug.cgi?id=352560
>> 
>> Best regards,
>> Eckart
>> 
>> From: p2-dev-bounces@xxxxxxxxxxx [mailto:p2-dev-bounces@xxxxxxxxxxx] On Behalf Of Pascal Rapicault
>> Sent: Montag, 18. Juli 2011 18:52
>> To: P2 developer discussions
>> Subject: Re: [p2-dev] Projector weight function
>> 
>> For a new install (which is the case in a tycho build), the intent is for the resolver to return the highest version available.
>> For addition on top of an install or update, the algorithm is a bit more complex but should favour the highest version of the things being in the transitive closure of what is being changed.
>> 
>> Could you please open a bug (https://bugs.eclipse.org/bugs/enter_bug.cgi?product=Equinox) with the necessary IUs to recreate the problem.
>> 
>> Thx
>> 
>> On 2011-07-14, at 4:46 PM, Langhuth, Eckart wrote:
>> 
>> 
>> Hi,
>> 
>> while investigating a problem resulting in bug
>> https://bugs.eclipse.org/bugs/show_bug.cgi?id=352081
>> I stumbled over the behavior of org.eclipse.equinox.internal.p2.director.Projector.
>> 
>> Out of curiosity. Is there a description of the weight function used to determine a solution?
>> In my example a feature includes a single plugin without a version constraint. (0.0.0)
>> The search scope contains two version of the required plugin.
>> The solution provided by the projector contains the plugin with the smaller version.
>> My assumption would have been to prefer a solution with latest plugin version.
>> The difference I see is that the higher version plugin defines more dependencies.
>> Is it intended to prefer a small installation over a new one?
>> 
>> Best regards,
>> Eckart
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