[mpich-devel] MPI_Reduce_scatter_block() with zero-size, NULL buffers.

[Thakur, Rajeev]

The alias check should be done only if the count is not zero, as in scatter.c or gather.c.

Rajeev

On Jul 6, 2014, at 6:34 AM, Balaji, Pavan <balaji at anl.gov> wrote:

> 
> Yes, this is intentional.  It’s an additional error check and is showing a bug in your user code.
> 
> You can suppress this error using the environment MPIR_CVAR_COLL_ALIAS_CHECK=0, but I wouldn’t recommend it.
> 
>  — Pavan
> 
> On Jul 6, 2014, at 6:29 AM, Lisandro Dalcin <dalcinl at gmail.com> wrote:
> 
>> This is from a build of master updated today and configured with
>> --enable-g=all. AFAICT, previous versions of MPICH did not generate
>> this error. Was this an intentional change?
>> 
>> Traceback (most recent call last):
>> File "/home/dalcinl/Devel/mpi4py-dev/test/test_msgzero.py", line 36,
>> in testReductions
>>   comm.Reduce_scatter_block(self.null_b, self.null_b)
>> File "Comm.pyx", line 714, in mpi4py.MPI.Comm.Reduce_scatter_block
>> (src/mpi4py.MPI.c:93219)
>> Exception: Invalid buffer pointer, error stack:
>> PMPI_Reduce_scatter_block(1182): MPI_Reduce_scatter_block(sbuf=(nil),
>> rbuf=(nil), recvcount=0, MPI_INT, MPI_SUM, MPI_COMM_SELF) failed
>> PMPI_Reduce_scatter_block(1142): Buffers must not be aliased
>> 
>> 
>> -- 
>> Lisandro Dalcin
>> ---------------
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