[mpich-devel] O(N^p) data

[Dan Ibanez]

Hello,

This may be a silly question, but the reason
I'm asking is to obtain a fairly definitive answer.
Basically, does MPICH have data structures
which are of size:
1) O(N)
2) O(N^2)
Where N is the size of MPI_COMM_WORLD ?
My initial guess would be no, because there
exist machines (Mira) for which it is not
possible to store N^2 bytes, and even N bytes
becomes an issue.
I understand there are MPI functions (MPI_alltoall) one can
call that by definition will require at least O(N) memory,
but supposing one does not use these, would the internal
MPICH systems still have this memory complexity ?

Thank you for looking at this anyway
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