-malign-double

[Lisandro Dalcin]

On Fri, Nov 13, 2009 at 11:09 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>
>   Good point, I have removed it.
>
>   I put it in because I wanted an easy way to test that PETSc double arrays
> are always 8 byte aligned (and the unaligned struct values were giving me
> lots of false alarms).
>
>   I guess we can test for double align on x86_64 systems.
>
>   Barry
>
> The IBM BlueGene doesn't like 4 byte aligned doubles and sends a bus error
> after a certain number are generated, Thus I was motivated to make PETSc a
> bit clearer on that.
>

But then the compiler in the BlueGene does not -malign-double by
default? That would be weird and annoying...

>
> On Nov 12, 2009, at 9:29 AM, Lisandro Dalcin wrote:
>
>> On Wed, Nov 11, 2009 at 11:02 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>>>
>>>  Satish,
>>>
>>>   gcc supports the option  -malign-double on some systems. Please add it
>>> to
>>> the flags that configure checks for c and c++ and have it added if it
>>> exists.
>>>
>>
>> Definitely -1. Why are you asking for this? On x86_64 this is the
>> default. In i386, this flag is likely going to break ABI's.
>>
>>
>> --
>> Lisandro Dalcín
>> ---------------
>> Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
>> Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
>> Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
>> PTLC - Güemes 3450, (3000) Santa Fe, Argentina
>> Tel/Fax: +54-(0)342-451.1594
>
>



-- 
Lisandro Dalcín
---------------
Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
PTLC - Güemes 3450, (3000) Santa Fe, Argentina
Tel/Fax: +54-(0)342-451.1594