[gentoo-dev] RFC: new global flag: index64

[gentoo-dev] RFC: new global flag: index64

[Michał Górny]

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Hello,

I'd like to propose adding a new global flag, with the following
proposed description:

index64 - Use the BLAS/LAPACK index64 API with 64-bit integers for array indexing

This is flag is not yet used in ::gentoo, it is part of ILP64 support
for BLAS/LAPACK that I'm working on [1].  It replaces the existing
'64bit-index' and 'index-64bit' flags, and extends them to the remaining
BLAS / LAPACK packages.

The idea is that the flag would be present in a semi-consistent manner
on two kinds of packages:

1) BLAS/LAPACK providers (blis, lapack, openblas and the virtuals),
where it will be locally redefined to indicate that it enables
installing / providing ILP64 BLAS / LAPACK libraries in addition
to the LP64 libraries,

2) BLAS/LAPACK consumers (such as numpy) where it will enable linking
against the ILP64 libraries instead of the LP64 libraries.


Short explanation for onlookers:

The "traditional" BLAS API (also called LP64) used 32-bit integers for
array indexing.  The ILP64 API (also known as index64 or simply "64-bit
BLAS") uses 64-bit integers instead, providing e.g. support for very
long arrays.


[1] https://github.com/gentoo/gentoo/pull/43776

-- 
Best regards,
Michał Górny

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Re: [gentoo-dev] RFC: new global flag: index64

[Matthias Maier]

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> index64 - Use the BLAS/LAPACK index64 API with 64-bit integers for array indexing


What about we make the use flag description slightly more general?


We have at least two additional scientific packages,

  sci-libs/dealii USE=int64
  sci-mathematics/petsc USE=int64

that have a use flag for 64bit ordinals/indexing. If we introduce a
global use flag "index64" we could use that one for the two packages as
well.


Best,
Matthias

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Re: [gentoo-dev] RFC: new global flag: index64

[Michał Górny]

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On Sun, 2025-09-14 at 13:29 -0500, Matthias Maier wrote:
> > index64 - Use the BLAS/LAPACK index64 API with 64-bit integers for array indexing
> 
> 
> What about we make the use flag description slightly more general?
> 
> 
> We have at least two additional scientific packages,
> 
>   sci-libs/dealii USE=int64
>   sci-mathematics/petsc USE=int64
> 
> that have a use flag for 64bit ordinals/indexing. If we introduce a
> global use flag "index64" we could use that one for the two packages as
> well.
> 

Sure.  Something like:

index64 - Enable 64-bit array indexing support

?

-- 
Best regards,
Michał Górny

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Re: [gentoo-dev] RFC: new global flag: index64

[Matthias Maier]

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> Sure.  Something like:
>
> index64 - Enable 64-bit array indexing support
>
> ?

Sounds good!

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Re: [gentoo-dev] RFC: new global flag: index64

[Sam James]

Matthias Maier <tamiko@gentoo.org> writes:

>> Sure.  Something like:
>>
>> index64 - Enable 64-bit array indexing support
>>
>> ?
>
> Sounds good!

WFM too and it solves the issue mgorny and I had discussed (felt a bit
too generic and like we might need a new name, but the new desc works).

sam

Re: [gentoo-dev] RFC: new global flag: index64

[Andreas K. Huettel]

Am Sonntag, 14. September 2025, 11:05:34 Westeuropäische Sommerzeit schrieb Michał Górny:
> Hello,
> 
> I'd like to propose adding a new global flag, with the following
> proposed description:
> 


Semi-related, just to mention another point where similar problems pop up:

Until now, on 32bit arches, Perl integers were in the Gentoo config 32bit too.

With Perl 5.42 we've silently switched that and now enforce 64bit Perl integers everywhere.

No need to take any action, and so far there have been no bugs I'm aware of.

-- 
Andreas K. Hüttel
dilfridge@gentoo.org
Gentoo Linux developer 
(council, comrel, toolchain, base-system, perl, libreoffice)
https://wiki.gentoo.org/wiki/User:Dilfridge