[petsc-dev] assuming sizeof(PetscInt) <= sizeof(PetscScalar)

[Peter Brune]

I'll get this stuff out of MatCoarsen and PCGAMG.  I will note that
users/developers wouldn't do this if there were a good way of taking
indices or proc/index pairs out of scatters.

One thought on --with-64-bit-indices --with-precision=single: reducing over 4
billion floats sounds like a bad time.

- Peter


On Sat, Feb 8, 2014 at 5:52 PM, Matthew Knepley <knepley at gmail.com> wrote:

> On Sat, Feb 8, 2014 at 5:40 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>>
>>    It appears people have been assuming sizeof(PetscInt) <=
>> sizeof(PetscScalar) right and left in the code (to take advantage of
>> VecScatter functionality). This is most definitely not true with
>> --with-64-bit-indices --with-precision=single
>>
>> MatGetBrowsOfAoCols_MPIAIJ
>> PCGAMGProlongator_Classical_Standard
>> maybe others
>>
>> VecScatters are for moving Vec elements around, they are not a
>> replacement for MPI calls!
>>
>> Please don't do this in the future.
>
>
> Please please please use PetscSF if you have regular layouts, and
> PetscSection for irregular layouts.
>
>   Matt
>
>
>>
>>    Barry
>>
>>
>
>
> --
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> -- Norbert Wiener
>
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