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Go Back   Linux Archive > Gentoo > Gentoo Portage Developer

 
 
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Old 03-03-2009, 06:55 AM
Pacho Ramos
 
Default emerge prefers to install x11-libs/qt:4 instead of ( x11-libs/qt-gui:4 x11-libs/qt-webkit:4 ) even when x11-libs/qt-gui:4 is already installed

El lun, 02-03-2009 a las 13:01 -0800, Zac Medico escribió:
> || ( ( x11-libs/qt-gui:4 x11-libs/qt-webkit:4 ) x11-libs/qt:4 )
>
> It's a variation of bug 161953 [1]. For this particular variation,
> at the moment I don't think there's a good way to distinguish that
> the choice on the left is the better choice.

>From my point of view, I think that portage should do something like
calculating how much a dep is already in the system, for example, in
this case, I have 50% of ( x11-libs/qt-gui:4 x11-libs/qt-webkit:4 )
already installed on my system while 0% of x11-libs/qt:4. Then,
( x11-libs/qt-gui:4 x11-libs/qt-webkit:4 ) would be a better option
because, hopefully, a user that has already installed a portion of this
dep, will prefer to maintain it installed

But, this is only theoretical as I am not a programmer and I don't know
if this could be implemented

> However, if we
> implement PROPERTIES=virtual [2] then we can use that to tag the
> qt-4 ebuild as a virtual and then we should get better behavior due
> to virtual lookahead mechanism that has been implemented for bug
> 141118 [3]. In the absence of PROPERTIES=virtual support, we'd have
> to use a more complex approach such as the "avoid redundant
> upgrades" algorithm suggested for bug 260225 [4].
>
> [1] http://bugs.gentoo.org/show_bug.cgi?id=161953
> [2]
> http://archives.gentoo.org/gentoo-dev/msg_9d449a18a96a25a547fcfd40544085cf.xml
> [3] http://bugs.gentoo.org/show_bug.cgi?id=141118
> [4] http://bugs.gentoo.org/show_bug.cgi?id=260225
> - --
> Thanks,
> Zac

This seems another option but, implementing previous one, would allow to
cover more possible cases

Best regards :-)
 
Old 03-04-2009, 06:55 AM
Pacho Ramos
 
Default emerge prefers to install x11-libs/qt:4 instead of ( x11-libs/qt-gui:4 x11-libs/qt-webkit:4 ) even when x11-libs/qt-gui:4 is already installed

El mar, 03-03-2009 a las 11:25 -0800, Zac Medico escribió:
>
> You're right. It's easy to says it in words but if you tried to
> actually implementing you'd find that the PROPERTIES=virtual concept
> simplifies the problem a lot and makes it possible to optimally
> solve some cases of bug 141118 that couldn't otherwise be solved
> optimally without the information that PROPERTIES=virtual provides.
>
> What we're talking about is a cost calculation and in order for the
> cost calculation to be as accurate as possible, we need to know
> which ebuilds have zero-cost to install (the virtual ones do not
> install anything directly so they are considered to have zero-cost
> in themselves). If you consider all ebuilds to have equal cost then
> your calculation won't be as accurate as it could be. Knowing which
> ebuilds are virtual gives a hint to the resolver that it should
> perform a "lookahead" in the cost calculation.
>
> We could implement a similar lookahead mechanism for non-virtual
> ebuilds, but it's more useful for the virtual ones. Backtracking
> (which isn't implemented yet but is planned for bug 1343) would also
> be useful for implementing additional cost optimizations (like the
> one for bug 260225).
> - --
> Thanks,
> Zac

No problem. Thanks for the explanation :-)
 

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