Bug#953116: [petsc-maint] 32 bit vs 64 bit PETSc

[Drew Parsons]

On 2020-05-23 20:27, Junchao Zhang wrote:
> On Sat, May 23, 2020 at 1:49 AM Drew Parsons <dparsons at debian.org>
> wrote:
> 
>> On 2020-05-23 14:18, Jed Brown wrote:
>>> 
>>> You don't need to change BLAS or MPI.
>> 
>> I see, the PETSc API allows for PetscBLASInt and PetscMPIInt
>> distinct
>> from PetscInt. That gives us more flexibility. (In any case, the
>> Debian
>> BLAS maintainer is already providing blas64 packages. We've started
>> discussions about MPI).
>> 
>> But what about MUMPS? Would MUMPS need to be built with 64 bit
>> support
>> to work with 64-bit PETSc?
>> (the MUMPS docs indicate that its 64 bit support needs 64-bit
>> versions
>> of BLAS, SCOTCH, METIS and MPI).

>  In MUMPS's manual, it is called full 64-bit. Out of the same memory
> bandwidth concern, MUMPS also supports selective 64-bit, in a sense it
> only uses int64_t for selected variables. One can still use it with
> 32-bit BLAS, MPI etc.  We support selective 64-bit MUMPS starting from
> petsc-3.13.0


Thanks Junchao.  Sounds like we can get started on providing 64-bit 
MUMPS and PETSc without needing to wait for MPI then.
That's good timing with 3.13.

Drew