What's the meaning of "chunk"?

[rongur@sohu_com]

Hi all,

I'm a newcomer of CAM.
I'm not very clear about the glossary "chunk" when trying to understanding some codes.
Anybody give me some hints?

Thanks in advance!

 

[rneale]

'chunk' refers to the particular group of atmospheric columns that is being operated on by a
particular process. It comes from parallel version of the model whereby each processor (or group of processors) will be given a bunch of columns to work with. These columns are determined by the domain decompostion in the model. A particular chunk may have columns that are not physically located adjacent to one another - for the purposes of obtaining the best model run efficiency.

The variable 'lchunk' refers to the index of the chunk of colums with 'ncol' number of columns in that particular chunk. The physical location of the particular gridpoints carried by a chunk are carried in the fortran type physics_state.
Namely physics_state%lchnk, physics_state%lat, physics_state%lon

See http://www.ccsm.ucar.edu/models/atm-cam/docs/phys-interface/phys-interface.pdf
for details