Hi. Yes, applications can span multiple nodes (e.g. in clusters and supercomputers), and is one of the main use cases of charm++/charmpy. The fact that you don'

Hi. Yes, applications can span multiple nodes (e.g. in clusters and supercomputers), and is one of the main use cases of charm++/charmpy. The fact that you don't see anything in the API or examples is that application code is basically transparent to the amount of processes that are launched. What determines the number of processes used is the launcher (e.g. charmrun, or something like aprun or ibrun on other systems). During initialization, the charmpy runtime will figure out internally how many charmpy processes are active in the job. With charmrun, you can launch multiple processes in one host, but also across multiple hosts (by ssh'ing into each one and spawning the processes). This is done automatically by charmrun assuming you specify a list of hosts (called nodelist, see http://charm.cs.illinois.edu/manuals/html/charm++/C.html http://charm.cs.illinois.edu/manuals/html/charm++/C.html). Again, the application code is not affected by this. Similarly, on other systems you can launch charmpy applications with the system job launcher (e.g. aprun, sbatch, ibrun…). We have done so for example on Cray supercomputers. It is simple enough but we have to update the documentation to at least show an example of this.