# 8.7. Diagnostics

PRRTE provides various diagnostic reports that aid the user in verifying and tuning the mapping/ranking/binding for a specific job.

The `:REPORT` qualifier to the `--bind-to` command line option can be used to report process bindings.

As an example, consider a node with:

- 2 processor packages,

- 4 cores per package, and

- 8 hardware threads per core.

In each of the examples below the binding is reported in a human readable format.

    $ prun --np 4 --map-by core --bind-to core:REPORT ./a.out
    [node01:103137] MCW rank 0 bound to package[0][core:0]
    [node01:103137] MCW rank 1 bound to package[0][core:1]
    [node01:103137] MCW rank 2 bound to package[0][core:2]
    [node01:103137] MCW rank 3 bound to package[0][core:3]

In the example above, processes are bound to successive cores on the first package.

    $ prun --np 4 --map-by package --bind-to package:REPORT ./a.out
    [node01:103115] MCW rank 0 bound to package[0][core:0-9]
    [node01:103115] MCW rank 1 bound to package[1][core:10-19]
    [node01:103115] MCW rank 2 bound to package[0][core:0-9]
    [node01:103115] MCW rank 3 bound to package[1][core:10-19]

In the example above, processes are bound to all cores on successive packages in a round-robin fashion.

    $ prun --np 4 --map-by package:PE=2 --bind-to core:REPORT ./a.out
    [node01:103328] MCW rank 0 bound to package[0][core:0-1]
    [node01:103328] MCW rank 1 bound to package[1][core:10-11]
    [node01:103328] MCW rank 2 bound to package[0][core:2-3]
    [node01:103328] MCW rank 3 bound to package[1][core:12-13]

The example above shows us that 2 cores have been bound per process. The `:PE=2` qualifier states that 2 CPUs underneath the package (which would be cores in this case) are mapped to each process.

    $ prun --np 4 --map-by core:PE=2:HWTCPUS --bind-to :REPORT  hostname
    [node01:103506] MCW rank 0 bound to package[0][hwt:0-1]
    [node01:103506] MCW rank 1 bound to package[0][hwt:8-9]
    [node01:103506] MCW rank 2 bound to package[0][hwt:16-17]
    [node01:103506] MCW rank 3 bound to package[0][hwt:24-25]

The example above shows us that 2 hardware threads have been bound per process. In this case `prun` is directing the DVM to map by hardware threads since we used the `:HWTCPUS` qualifier. Without that qualifier this command would return an error since by default the DVM will not map to resources smaller than a core. The `:PE=2` qualifier states that 2 processing elements underneath the core (which would be hardware threads in this case) are mapped to each process.

    $ prun --np 4 --bind-to none:REPORT  hostname
    [node01:107126] MCW rank 0 is not bound (or bound to all available processors)
    [node01:107126] MCW rank 1 is not bound (or bound to all available processors)
    [node01:107126] MCW rank 2 is not bound (or bound to all available processors)
    [node01:107126] MCW rank 3 is not bound (or bound to all available processors)

Binding is turned off in the above example, as reported.