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

[Balaji, Pavan]

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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