On 29.11.2012 21:11, Ralph Sennhauser wrote: > On Thu, 29 Nov 2012 17:09:34 +0100 > justin <j...@gentoo.org> wrote: > >> On 29/11/12 16:51, Ian Stakenvicius wrote: > [...] >>> ..ok remind me again what the .pc files provide you? this is so >>> that you can have slotted blas providers and various packages can >>> choose their preferred one instead of having to use the eselected >>> one? or... >>> >> >> Not exactly. >> The user can choose for each package newly by eselecting the wanted >> implementation. This is the user side. From the pm side we ensure that >> the choice is really respected by linking against package specific >> names [1] instead of the generic ones e.g. libblas.so. And this can be >> achieved in an easy way by using pkg-config. >> >> justin >> >> 1) >> # eselect blas set atlas-threads >> # pkg-config --libs blas >> -lptf77blas -lm -latlas -lpthread >> >> # eselect blas set reference >> # pkg-config --libs blas >> -lrefblas >> > > This immediately bears the following questions: > > * How do you ensure the linked against implementation doesn't get > depcleaned? revdep-rebuild maybe?
portage handles this fine. > > * How do you let users configure the implementation to be used on a per > package basis? Interrupt an emerge world to set the appropriate > implementation for the next few packages? > The Standard user will get reference implementation and has no problem. Setting individual implementation on per package basis needs to be considered as they-know-what-they-are-doing. Otherwise you don't know which implementation to choose .
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