Re: RFC: Naming convention for ILP64 variant of BLAS/LAPACK
- Date: Mon, 22 Oct 2018 15:07:10 +0000
- From: Mo Zhou <lumin@xxxxxxxxxx>
- Subject: Re: RFC: Naming convention for ILP64 variant of BLAS/LAPACK
Hi Wookey and Bastian,
On Sun, Oct 21, 2018 at 06:51:16PM +0100, Wookey wrote:
> On 2018-10-21 17:16 +0200, Bastian Blank wrote:
> > Hi
> > On Sun, Oct 21, 2018 at 09:51:15AM +0000, Mo Zhou wrote:
> > > about naming convention of SONAME and package name.
> > >
> > > As discussed in , Debian will need a set of ILP64 interface
> > > to BLAS/LAPACK in the future.
> > Could you please describe what you mean? All 64-bit Debian
> > architectures are LP64. So building a single binary using ILP64 will
> > even break the ABI for glibc and it will most likely not run very far.
> > (A file descriptor is defined as "int", so even the most basic file
> > calls will be incompatible.)
I missed some points in the original post. The proposal meant to add
a new set of BLAS/LAPACK packages that are compiled in ILP64, and the
existing BLAS/LAPACK API/ABI won't be changed and nothing will break.
Here is a detailed example for demonstration
bin:libopenblas-base (LP64, won't be changed at all)
bin:libopenblas-dev (LP64, won't be changed at all)
bin:libopenblas-ilp64 (ILP64, newly-added)
bin:libopenblas-ilp64-dev (ILP64, newly-added)
So there is no "ABI bump" but just "adding a new set of ABI". At the
same time, it won't result in any transition or breakage.
> I wondered about this. The mail said that the BLAS/LAPACK ABIs do not
> change, so I presumed that this was about internal data layouts for
> the data being passed which. But reading the bugreps it does sound
> like just a new ABI using ILP64. That would be properly done using
> multiarch or multilib paths, and needs some thought about how best to
> lay things out and what else would be needed to make it work.
The simplest solution is just to create a separate ABI with different
name and different package name. And it introduces the least overhead.
> Are any
> other packages likely to start wanting to use ILP64 ABIs? I guess it's
> very much an 'HPC' sort of thing at the moment.
> So yeah, some clarification in order I think, and an explanation of use-cases.
HPC is indeed a related use case. I don't know any other package that
would need such an ILP64 BLAS/LAPACK interface except for Julia.
Actually by default Julia uses ILP64 version of openblas instead of
LP64, see [julia-ilp64-default].
Here are some references:
The Intel MKL ILP64 libraries use the 64-bit integer type (necessary
for indexing large arrays, with more than 231-1 elements), whereas
the LP64 libraries index arrays with the 32-bit integer type.
Julia upstream and fedora chose a different solution... they mangled
the BLAS/LAPACK symbol names by adding an "64_" suffix. However,
Julia is the only upstream that use this mangling rule in practice,
and maybe some other ILP64-capable BLAS/LAPACK providers doesn't
allow easy name mangling. That means if we still want to take
advantage from the update-alternatives mechanism, we should not
mangle the symbol names.
src:intel-mkl is currently the only ILP64-ready BLAS/LAPACK provider
in the archive, and it doesn't mangle symbol names.