[mpich-devel] MPIR_ERRTEST_ARGNULL and count=0 (or type_size=0)

[Jeff Hammond]

Hi Bill,

When I went looking for examples of ERRTEST_ARGNULL, I recall at least
most of them being for internally allocated buffers, i.e. used in the
MPICH-ized version of "void * b = malloc(); assert(b!=NULL);"

I'll look into making both of the changes you describe.  It is
obviously going to be much more useful to have ERRTEST_USERBUFFER
return a message like ERRTEST_ARGNULL.

Best,

Jeff

On Mon, Jun 3, 2013 at 8:25 AM, William Gropp <wgropp at illinois.edu> wrote:
> The reason that you are not seeing the MPIR_ERRTEST_USERBUFFER is that the
> original intent of the design is that easy error tests are carried out in
> the error test block and anything else must be handled elsewhere.  For
> example, some of the group operations have consistency checks in the body of
> the code, rather than in the error test block.  Because MPI_BOTTOM with an
> MPI Datatype containing non-zero offsets is always valid, the simple checks
> for NULL were originally not performed in any of the routines.  The
> ERRTEST_USERBUFFER check will catch many (though not all) null buffers at
> relatively low cost, though since other parts of the code must also check
> for null, it should not be considered necessary or sufficient.
>
> Its probably worth adding a comment that it is incorrect to use
> ERRTEST_ARGNULL for communication buffers in every routine that has one,
> since this issue comes up every few years.
>
> Also, the ERRTEST_USERBUFFER should include the parameter name and add an
> error message that includes the parameter name, since many routines have
> multiple communication buffers to which this can be applied.
>
> Bill
>
> William Gropp
> Director, Parallel Computing Institute
> Deputy Director for Research
> Institute for Advanced Computing Applications and Technologies
> Thomas M. Siebel Chair in Computer Science
> University of Illinois Urbana-Champaign
>
>
>
>
> On May 30, 2013, at 6:40 AM, Jeff Hammond wrote:
>
> The check for NO_OP in *get_accumulate was most certainly present.
> That was the first thing I checked when
> MPI_Get_accumulate(MPI_REPLACE) failed to behave like MPI_Get w.r.t.
> ARMCI-MPI test codes.
>
> I'm going to supplement the RMA test suite so that this issue and ones
> like it would have been caught by MPICH rather than waiting until the
> very last ARMCI-MPI test to be revealed.
>
> Jeff
>
> On Thu, May 30, 2013 at 4:53 AM, Jim Dinan <james.dinan at gmail.com> wrote:
>
> Ugh, deep shame upon me and whoever reviewed my patch!  Lisandro is
>
> correct.  :)
>
>
> For accumulate ops, the op can also cause a buffer to be ignored (e.g.
>
> GACC/FOP with NO_OP).  I think there is code to handle this, but keep an
>
> eye out for it.
>
>
> ~Jim.
>
>
> On 05/29/2013 03:08 PM, Lisandro Dalcin wrote:
>
> On 29 May 2013 22:49, Jeff Hammond <jhammond at alcf.anl.gov> wrote:
>
> It seems that I didn't understand MPI_BOTTOM completely, so the error
>
> checks needed to be different than described below, but the high-level
>
> issues are the same.
>
>
> Interested parties may consult
>
> http://trac.mpich.org/projects/mpich/ticket/1863 for details and
>
> further discussion.
>
>
>
> Please take a look at the macro MPIR_ERRTEST_USERBUFFER .
>
>
>
>
> --
>
> Lisandro Dalcin
>
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>
>
>
> --
> Jeff Hammond
> Argonne Leadership Computing Facility
> University of Chicago Computation Institute
> jhammond at alcf.anl.gov / (630) 252-5381
> http://www.linkedin.com/in/jeffhammond
> https://wiki.alcf.anl.gov/parts/index.php/User:Jhammond
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>
>



-- 
Jeff Hammond
Argonne Leadership Computing Facility
University of Chicago Computation Institute
jhammond at alcf.anl.gov / (630) 252-5381
http://www.linkedin.com/in/jeffhammond
https://wiki.alcf.anl.gov/parts/index.php/User:Jhammond
ALCF docs: http://www.alcf.anl.gov/user-guides