-malign-double

[Barry Smith]

On Nov 14, 2009, at 4:01 PM, Lisandro Dalcin wrote:

> 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...

    BlueGene has two compilers, IBM's XLc and gcc. I do not know if  
either of them are rigged to 8 byte align by default.

   Barry

>
>>
>> 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