[MITgcm-devel] mnc and "global" files

[Jean-Michel Campin]

Hi Baylor, Ed, and others,

> So, you can have four processors
> per tile which requires an additional indexing...which I recommend
> denoting with a p.

No. You can have several tiles per processor, but not more than
1 processor per tile.

And regarding the sync. of pickup/state/tave, I am not sure that I fully
understand the point, and right now, I don't see it as an improvement.
And suppose we have the possibility to decide when to cut and create
a new state.*.nc file (=as Ed proposed), you can always set this
frequency = to (a multiple of) the pickup frequency, and this will do
what you want. Does this make sense or did I miss something ?

Ed, I have 2 remarks/questions:
1) What do we do when there is only 1 face (90 % of the MITgcm users
 don't run a "cube" like set-up, and don't use exch2):
   a) do we drop the face ".f000001." piece ?
or b) do we keep it whatever the set-up is ?

2) I don't recommend to use 6 digits for the face number, and
I think 3 is enough (i.e. .f001. , .f002. ...):
- this is specially relevant if we choose to always have this face
  number (solution b of question 1) in the file name.
- this will make things more clear: global file / face =
  larger file but fewer of them, and with shorter name, as opposed
  to local files per tile.

3) my recent experience with fields that don't fit into the
Nx x Ny array structure (like vorticity on the cube), is that
it's much more convenient to use a compressed form (nc*nc*6+2,Nr)
than a faced structure (nc+1,nc+1,Nr,6) (<- especially the face
after the k index is a pain). One of the advantages of the
compressed form is that it can also be used for unstructure grids.
This comes more as a post-processing / matlab issue.
But regarding the choice of global file / face, I just want to be
sure that we are aware of the alternative (= toward unstructure
grids: Nb of horizontal grid points x Nb of levels), and that we
don't change your mind before finishing the implementation of
the 1rst choice.

Jean-Michel