Quoting Thomas Kahle <tomka@g.o>:

> On 17:27 Wed 30 May 2012, P Purkayastha wrote:
>> On 05/30/2012 05:07 PM, Thomas Kahle wrote:
>> > Hi,
>> > I'm trying to build sage on gentoo but I get a conflict:
>> >
>> > !!! Multiple package instances within a single package slot have 
>> been pulled
>> > !!! into the dependency graph, resulting in a slot conflict:
>> >
>> > dev-python/numpy:0
>> >
>> >    (dev-python/numpy-1.5.1::sage-on-gentoo, ebuild scheduled for 
>> merge) pulled in by
>> >      ~dev-python/numpy-1.5.1 required by 
>> (sci-mathematics/sage-5.0-r1::sage-on-gentoo, ebuild scheduled for 
>> merge)
>> >
>> >    (dev-python/numpy-1.6.0::gentoo, ebuild scheduled for merge) 
>> pulled in by
>> >      >=dev-python/numpy-1.5[lapack] required by 
>> (sci-libs/scipy-0.9.0-r1::gentoo, ebuild scheduled for merge)
>> >
>> > Any suggestions?
>> >
>> > Thanks!
>> > Thomas
>> >
>>
>> The latter package scipy depends on >=numpy-1.5 whereas sage depends 
>> on =numpy-1.5.1. So, simply mask the higher versions of numpy:
>>
>> If you have /etc/portage/package.mask directory then,
>>
>> echo ">dev-python/numpy-1.5.1" >> /etc/portage/package.mask/mask_numpy
>>
>> otherwise
>>
>> echo ">dev-python/numpy-1.5.1" >> /etc/portage/package.mask
>
> ... and now it pulls in eselect-cblas and gsl which are blocking each other:
>
> [blocks B      ] app-admin/eselect-cblas ("app-admin/eselect-cblas" 
> is blocking sci-libs/gsl-1.15-r2)
>
>  * Error: The above package list contains packages which cannot be
>  * installed at the same time on the same system.
>
>   (app-admin/eselect-cblas-0.1::gentoo, ebuild scheduled for merge) 
> pulled in by
>     app-admin/eselect-cblas required by 
> (sci-libs/cblas-reference-20030223-r4::gentoo, ebuild scheduled for 
> merge)
>
>   (sci-libs/gsl-1.15-r2::science, installed) pulled in by
>     sci-libs/gsl required by (media-gfx/inkscape-0.48.2::gentoo, installed)
>     >=sci-libs/gsl-1.15 required by 
> (sci-mathematics/sage-5.0-r1::sage-on-gentoo, ebuild scheduled for 
> merge)
>
I think that's a different problem. You are using blas stuff from the science
overlay but the version of cblas-reference from the main tree as a higher
version number than the one from the science overlay (3. something?). So you
probably have to mask sci-libs/cblas-reference::gentoo.

For your original problem, yes portage should solve the conflict, this is very
strange, are numpy or scipy part of your world file?

Francois