First, "long unsigned int window_size=2147483648" is not correct. They type you need to use there is MPI_Aint. The syntax of this function is int MPI_Win_allocate_shared(MPI_Aint size, int disp_unit, MPI_Info info, MPI_Comm comm, void *baseptr, MPI_Win *win) It may be true that "long unsigned int" is safely case to MPI_Aint, but that's a very danger way to write code and it may be broken on some platforms. In any case, everything above 2^31 is probably not okay. Unless absolutely every integer type used in the code paths you are hitting is size_t (or equivalent) and not int, you're going to hit overflow somewhere. Maybe I'm wrong, but you should verify (as a debugging mechanism, not in general) that MPI_Win_allocate_shared is behaving as desired by memset-ing the resulting data (mem) to verify that you're actually getting e.g. 2^34 bytes back. If /dev/shm is 4G, I'm not sure how that's possible but maybe the implementation doesn't use that. I'm going to be on a plane today but I'll run your code on my machine and try to figure out more about how "count-safe" MPI_Win_allocate_shared is. Jeff PS Installing MPICH in ~/git/openmpi is just dirty :-) On Fri, Jun 7, 2013 at 5:50 AM, Weise Steffen <[email protected]> wrote:

Dear mailing-list,

this is my first time posting here. I found that with version 3.0.4 using MPI_Win_allocate_shared i get an error when using a size exactly 2^31 everything below and above is ok. Though i also had the same issue with 2^34. Some kind of division or type conversion seems to be off. (/dev/shm has 4G so it is not a size issue.. i know what those errors look like)

I attach my code and the output i get on a linux (debian 6.0) 64 bit machine (same issue on a mac though) .

I'll be happy to provide more machine details or everything you guys need to analyse whats going on.

with kind regards, Steffen Weise

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-- Jeff Hammond Argonne Leadership Computing Facility University of Chicago Computation Institute [email protected] / (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