out of curiosity, why would you want to do that ?
----- Original Message -----
Is it easy to update ompi_datatype_is_valid to judge invalid
datatypes, such as -1?
Dahai
On Fri, Jun 2, 2017 at 9:00 AM, Gilles Gouaillardet <gilles.
gouaillar...@gmail.com> wrote:
MPI_Datatype is a opaque handler, and -1 is a (signed) integer,
so
what you are trying is very likely to have an undefined behavior
per
the standard.
if this seems to work with MPICH, this is not portable anyway,
and
will very likely cause a crash with OpenMPI
Cheers,
Gilles
On Fri, Jun 2, 2017 at 10:41 PM, Dahai Guo <dahai....@gmail.com>
wrote:
> so you are saying that a user should NOT define send/recv data
type as -1,
> in openmpi?
>
> Dahai
>
> On Thu, Jun 1, 2017 at 6:59 PM, Gilles Gouaillardet <gilles@
rist.or.jp>
> wrote:
>>
>> +1
>>
>>
>> MPI_Datatype is an opaque handler, and in Open MPI, this is
an
>> ompi_datatype_t *
>>
>> so we can only test for NULL pointers or MPI_DATATYPE_NULL
that cannot be
>> used per the standard.
>>
>>
>> fwiw, and iirc, MPICH made an other design choice and MPI_
Datatype is a
>> number, so the mpich equivalent of ompi_datatype_is_valid()
>>
>> might be able to handle random values without crashing.
>>
>>
>> Cheers,
>>
>>
>> Gilles
>>
>>
>> On 6/2/2017 7:36 AM, George Bosilca wrote:
>>>
>>> You have to pass it an allocated datatype, and it tells you
if the
>>> pointer object is a valid MPI datatype for communications (
aka it has a
>>> corresponding type with a well defined size, extent and
alignment).
>>>
>>> There is no construct in C able to tell you if a random
number if a valid
>>> C "object".
>>>
>>> George.
>>>
>>>
>>> On Thu, Jun 1, 2017 at 5:42 PM, Dahai Guo <dahai.guo@gmail.
com
>>> <mailto:dahai....@gmail.com>> wrote:
>>>
>>> Hi,
>>>
>>> if I insert following lines somewhere openmpi, such
>>> as ompi/mpi/c/iscatter.c
>>>
>>> printf(" --- in MPI_Iscatter\n");
>>> //MPI_Datatype dt00 = (MPI_Datatype) MPI_INT;
>>> *MPI_Datatype dt00 = (MPI_Datatype) -1;*
>>> if(*!ompi_datatype_is_valid(dt00)* ) {
>>> printf(" --- dt00 is NOT valid \n");
>>> }
>>>
>>> The attached test code will give the errors:
>>>
>>> *** Process received signal ***
>>> Signal: Segmentation fault (11)
>>> Signal code: Address not mapped (1)
>>> Failing at address: 0xf
>>> [ 0] [0x3fff9d480478]
>>> ...
>>>
>>> Is it a bug in the function *ompi_datatype_is_valid(..)
*? or I
>>> miss something?
>>>
>>> Dahai
>>>
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>>>
>>>
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>>
>>
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>
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