Not saying we won't change the behavior. Just saying the user can't expect a
particular alignment as there is no guarantee in the standard. In Open MPI we
just don't bother to align the pointer so right now so it naturally aligns as
64-bit. It isn't about wasting memory.
Also remember that by
Given that this seems to break user experience on a relatively frequent
basis, I’d like to know the compelling reason why MPI implementers aren’t
willing to do something utterly trivial to fix it.
And don’t tell me that 16B alignment wastes memory versus 8B alignment.
Open-MPI “wastes” 4B relative
That is probably it. When there are 4 ranks there are 4 int64’s just before the
user data (for PSCW). With 1 rank we don’t even bother, its just malloc
(16-byte aligned). With any other odd number of ranks the user data is after an
odd number of int64’s and is 8-byte aligned. There is no require
Hello Open MPI team,
I'm looking for the recommended way to produce a debug build of Open MPI v3.0.1
that compiles with “-g -O0” so that I get accurate debug info under a debugger.
So far, I've gone through the following sequence. I started with CFLAGS="-g
-O0" on make:
shell$ ./configure --p
Martin,
You say that you allocate shared memory, do you mean shared memory
windows? If so, this could be the reason:
https://github.com/open-mpi/ompi/issues/4952
The alignment of memory allocated for MPI windows is not suitable for
128bit values in Open MPI (only 8-byte alignment is guarante
