Plugin to show hardware info

[amartyads]

I was planning to write a plugin that shows hardware info. At minimum, it would show which rank is on which node. Creating this issue for brainstorming and for input from others.

My ideas so far:

1. Accept a filename in xml. If there is filename, print the info in a CSV/TSV/whatever out current standard is. Otherwise, pretty-print to stdout.
2. The info should be (at the very least)
   1. The rank (output of MPI_Comm_rank)
   2. The processor_name (output of MPI_Get_processor_name)
3. Additional info we can have:
   1. The lower and upper bound of the subdomain in this rank (stepping on the DecompWriter's toes a bit here)
4. The info is only printed/written at beginning of simulation. To deal with load balancing, we can either add a print frequency in the xml, or we can trigger a write whenever a load balance occurs. For this, I would add a bool called balancedInLastTImestep somewhere (probably in DomainDecompBase) that is set once a rebalance is done, and reset at the beginning of the next timestep. (NB: I would like to have this bool anyway in the future for mamico reasons, but it's not necessary in this specific issue).

Any other input/ideas?

[FG-TUM]

Why duplicate the functionality of the DecompWriter?

[amartyads]

I could just merge this idea into DecompWriter, make it also write MPI_Get_processor_name somewhere. Would that be better than writing a separate plugin?

[FG-TUM]

I think if you just want to show the rank to hardware mapping this should be a standalone plugin. You could also include each ranks thread to core mapping.

[rubenhorn]

I agree with @FG-TUM that the plugins should probably stick to their main responsibility… I'm not a big fan of merging this with the decomp plugin.
Also, maybe we should output to a different format than simple tabular/text file.
JSON/YAML/XML allows for hierarchical structure, which is A) easier to parse in post-processing IMHO and B) accommodates additional hardware info on different systems (future-proof).