[mpich-discuss] MPI_File_write_at_all issue

[Mohamad Chaarawi]

Hello all,

I've been trying to figure out what I'm doing wrong while implementing a
simple test case using MPI_File_write_at_all.

I have attached the test case, which basically creates a file view in a
way where each process writes/reads 4 integers 4 times.
In a 2 process scenario the file view is:

(PROC 0 --> 4 ints)(PROC 1 --> 4 ints)(PROC 0 --> 4 ints)(PROC 1 --> 4
ints)(PROC 0 --> 4 ints)(PROC 1 --> 4 ints)(PROC 0 --> 4 ints)(PROC 1
--> 4 ints)

When using MPI_File_write_at_all with an offset of 16 (which means 16*4
= 64bytes) since the etype used to create the file view is an int, and
each process writing 16 integers, I would expect the size of the file to
be 256, since each process is starting to write 16 integers into the
file view, or basically skipping one iteration of the file view into the
file.. however Im getting a file size of 240.

Im not sure if Im misunderstanding the way write_at_all works or there
is some bug somewhere..

Im using the Romio version included in the Open Mpi trunk.

Thank you,
Mohamad

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