Jeff Squyres wrote on Thu, 8 Jul 2010 at 10:34:46

On Jul 8, 2010, at 1:32 PM, Quincey Koziol wrote:

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As an aside, can count ever be larger than size_t?

I would imagine so - on a 32-bit CPU/system with a 64-bit file system.

Oh ya, that whole filesystem thing. :-)

But even on a 32-bit system, you can't do more than a 32-bit file access at a time. Even if you created a datatype that represented more than 2^31 bytes, you wouldn't be able to use it in any of the functions because you wouldn't be able to transfer that much data at once.

But still -- why do you ask? I am hoping you don't plan to mention "size_t" in the standard at all...

I ask because MPI_Size (for MPI_Type_size, MPI_Pack_size, and the position parameters of MPI_Pack/Unpack) would likely be size_t - how could you use more than the addressable space? I also think that MPI_Count would reasonably be size_t also, since I pretty firmly believe that MPI_Count and MPI_Size should be the same type. -Fab