CAM debugging techniques

This page contains techniques which are useful when the model is crashing. Note that this is not a page about using parallel debuggers since availability is often limited.

Debugging Techniques

• CAM Snapshot
• Stopping the model
• cam_pio_dump_field
• pbuf_dump_pbuf

CAM Snapshot

Stopping the model

cam_pio_dump_field

cam_pio_dump_field is a function which immediately writes a NetCDF file with information from a field. For example:

   call cam_pio_dump_field('CLD', 1, pcols, 1, pver, cld)

will write the field, cld, to a file called CLD_dump_<##>.nc where <##> is a number starting at one and increasing as this call is repeated. The file simply contains the contents as a 3-dimensional array where the first two dimensions are given by the bounds (1:pcols and 1:pver) and the third dimension is the MPI task number (1:npes).

cam_pio_dump_field can also handle 3, 4, and 6-dimensional fields, just call the function with the appropriate number of bounds for the field.

Note that by default, cam_pio_dump_field collects the bounds from all MPI tasks and uses the largest range for the NetCDF file. To skip this step, set the optional variable, compute_maxdim_in, to .false..

pbuf_dump_pbuf

pbuf_dump_pbuf is similar to cam_pio_dump_field in that it immediately writes NetCDF files. The main difference is that is cannot be called from a threaded region and requires access to the full pbuf (aka the pbuf2d variable). The call is:

pbuf_dump_pbuf(pbuf2d, name, num)

where pbuf2d is the full pbuf, name is an optional name to be added to each filename, and num is an optional integer to be added to each filename.

pbuf_dump_pbuf then writes a NetCDF file for each field in the pbuf for this run. The file format is the same for cam_pio_dump_field (see above).