Is it possible to change any MPI settings during runtime? The only similar thing I know about is manipulation with intra and inter-communicators (docs).
Do you know about some other things? I'm thinking about changing PATH, MPIEXEC_TIMEOUT, prefix of PATH etc.
I need it just for demonstration purposes for one project, so anything that can be set during runtime, is enough :-)
The now standard way of doing this is with control variables (CVARs). These are all implementation specific, so you'll have to look in the documentation for your particular library. Often, these can be set with an environment variable.
For example, in MPICH 3.2, there is an environment variable called MPIR_CVAR_ASYNC_PROGRESS that allows you to turn on and off asynchronous progress at runtime. These things are documented in the tarball in a file called README.envvar.
These things will not be consistent between implementations so you'll have to be careful about names depending on where you are running. For instance, in Open MPI, I'd imagine that most of these environment variables will be prefixed with something like OMPI_something since that's more in line with the naming scheme used by that project.
