[MPICH2 Req #4033] RE: [mpich2-dev] Bug in ch3 MPIDI_Accumulate()?

[William Gropp]

This is a reminder that we need to review the coverage tests.  For  
example, the local copy for put also does not appear to be tested.  See

http://www.mcs.anl.gov/research/projects/mpich2/todo/coverage/ 
ch3:sock/src/mpid/ch3/src/ch3u_rma_ops.c.htm

Bill
On Apr 4, 2008, at 3:27 PM, Rajeev Thakur wrote:

> David,
>            You are right. There is a bug. It didn't get caught so  
> far because the test suite doesn't have a test for an accumulate  
> with derived datatype at origin, basic datatype at target, and  
> origin = target.
>
> Rajeev
>
> From: owner-mpich2-dev at mcs.anl.gov [mailto:owner-mpich2- 
> dev at mcs.anl.gov] On Behalf Of David Gingold
> Sent: Wednesday, April 02, 2008 3:23 PM
> To: mpich2-dev at mcs.anl.gov
> Subject: [mpich2-dev] Bug in ch3 MPIDI_Accumulate()?
>
> I ran into this problem in code that I cribbed from the ch3  
> implementation. I've not verified that it happens in ch3, but it  
> seems, by inspection, that it probably does:
>
> In MPIDI_Accumulate() (ch3u_rma_ops.c), in the case where  
> target_rank == rank and the origin and target datatypes are not  
> both pre-defined, the code does this:
>
> MPID_Datatype_get_ptr(target_datatype, dtp);
> vec_len = dtp->n_contig_blocks * target_count + 1;
>
> The trouble is that we'll hit this case where the origin type is  
> derived and the target type is pre-defined. And  
> MPID_Datatype_get_ptr() isn't workable for pre-defined datatypes.  
> So dtp->* will evaluate to zero. That causes grief when we  
> reference dtp->eltype a few lines down.
>
> I think the simple fix is to add separate cases in here for when  
> target_datatype is predefined. But I also spotted the code in  
> MPIR_Datatype_builtin_fillin(), which, if called, would seem to  
> make MPID_Datatype_get_ptr() become valid for built-in datatypes.  
> Is there a reason why MPIR_Datatype_builtin_fillin() isn't simply  
> called inside MPI_Init() somwehere?
>
> -dg
>
> --
> David Gingold
> Principal Software Engineer
> SiCortex
> Three Clock Tower Place, Suite 210
> Maynard MA 01754
> (978) 897-0214 x224
>
>
>

William Gropp
Paul and Cynthia Saylor Professor of Computer Science
University of Illinois Urbana-Champaign


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