PETSc in double-double and quad-double...

[Matthew Knepley]

On Wed, Nov 4, 2009 at 2:06 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
>   This is tricky because some C/C++ compilers long double uses 128 bits of
> space but actually (on Intel) only uses 80 of the bits (those are the bits
> that floating point unit handles). So you do not really get 128 bits. Also
> MPI may not properly handle the 128 bit doubles.
>

I figured that his types were just C++ types once he said they were provided
by a package.


>   I am investigating qd now. Is there any MPI implementation that uses qd?
> Do you need MPI?
>

Can't we just make a type the correct number of bytes long?

  Matt


>   Barry
>
>
>
> On Nov 4, 2009, at 1:33 PM, Matthew Knepley wrote:
>
>  If you are alright with EVERYTHING running with that, it already works.
>> Just set PetscScalar
>> to that type. I would help you setup a configure switch for it if needed.
>>
>> If you only want it for some operations, we would have to hear more
>> specifics.
>>
>>  Thanks,
>>
>>    Matt
>>
>> On Wed, Nov 4, 2009 at 10:45 AM, Todd Munson <tmunson at mcs.anl.gov> wrote:
>>
>> Barry and Matt,
>>
>> I was wondering how hard it would be to modify PETSc to support
>> double-double and quad-double arithmetic using the QD package
>> from LBL?
>>
>> Its looking more and more likely that I may need this functionality for
>> some upcoming projects that have bad scaling issues and I don't want to have
>> to reimplement KSP and PC methods...
>>
>> Cheers, Todd.
>>
>>
>>
>>
>> --
>> 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
>>
>
>


-- 
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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20091104/eb82322e/attachment.html>