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From: Scott Atchley (atchley_at_[hidden])
Date: 2007-07-10 13:40:24

On Jul 10, 2007, at 1:14 PM, Christopher D. Maestas wrote:

> Has anyone seen the following message with Open MPI:
> ---
> warning:regcache incompatible with malloc
> ---
> <snip>
> ---
> We don't see this message with mpich-mx-1.2.7..4

Hi Chris,

MX has an internal registration cache that can be enabled with
MX_RCACHE=1 or disabled with MX_RCACHE=0 (the default before MX-1.2.1
was off, and starting with 1.2.1 the default is on). If it is on, MX
checks to see if the application is trying to override malloc() and
other memory handling functions. If so, it prints the error that you
are seeing and fails to use the registration cache.

Open MPI can use the regcache if you set MX_RCACHE=2. This tells MX
to skip the malloc() check and use the cache regardless. In the case
of Open MPI, this is believed to be safe. That will not be true for
all applications.

MPICH-MX does not manage memory, so MX_RCACHE=1 is safe to use unless
the user's application manages memory.


Scott Atchley
Myricom Inc.