[mpich-discuss] ROMIO: 2 phase IO method and error handling

[Rob Latham]

On Mon, Aug 23, 2010 at 04:35:36PM +0200, Pascal Deveze wrote:
> I discovered that I can read after the end of file !
> 
> After a look in the romio source code, I see that the "2 phase IO"
> method for read:
> 1) Does not return the right count value in the status
...
> Has anybody an idea on how to correct this ?

well, i've got an idea but it's not great.

We could report how much data each process actually read, but that
would return surprising results in this test: rank 0 reads 5 bytes but
rank 1 reads none. 

So we have to communicate the fact that we had a short read.  I guess
another allreduce in the collective I/O path won't be so bad, but I
still need to think some more about how to react to the fact that one
aggregator had a short read.

==rob

-- 
Rob Latham
Mathematics and Computer Science Division
Argonne National Lab, IL USA