[mpich-discuss] Funky MPI_File_write_at Parameters

[Ellis H. Wilson III]

Hi all,

Back with another odd-ball tracing question.  When I trace IOR using the
following parameters:

IOR -a MPIIO -b 4m -t 2m -i 1 -o pvfs2:/tmp/pvfs2client/test.dat

I get what I feel are very odd tracing parameters shown below for the
MPI_File_write_at function:

MPI_File_write_at(0x9ae9ab0, 4194304, NULL, -1211088896, 0x200000,
0x4c00010d

Now there are 6 parameters, which I expected from the specification, but
it seems to me like they might be out of order.  P1 seems to be the file
handle, P2 seems to be the offset, P3 indicates my lack of a buffer,
which I believe to be fine, but P4 is the real oddity as the count
argument should be nonnegative and here we have -1211088896.  0x200000
corresponds to 2097152 decimal so I would think that makes more sense as
a count (-t means transfers of 2megs, which is dead on for that) and I
know the last parameter shown should have been my datatype and sitting
in position 5, but it is in 6.  Status object is nowhere to be found as
it ends there (unless status object somehow got switched to position 4,
which is my guess currently).  These parameters are similarly weird for
MPI_File_read_at.

I am tracing MPI calls using LANL-Trace and I've looked through the code
for LANL-Trace and IOR and everything seems to check out except the
difference between how IOR internally handles offset and count (both
long long int) and how mpich handles offset and count (int).  I don't
think this is the issue however as I've added some quick casts to IOR
and the problem persists.  I am truly lost on why this is happening, but
then again perhaps I am misunderstanding something fundamental about this.

If anyone can confirm that at the very least, I am right in thinking
this looks weird it would be very helpful.

Thanks,

ellis